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* [Bug c/18065] New: wrong built-in functions selected
@ 2004-10-19 20:22 schlie at comcast dot net
2004-10-19 20:27 ` [Bug c/18065] " schlie at comcast dot net
` (32 more replies)
0 siblings, 33 replies; 40+ messages in thread
From: schlie at comcast dot net @ 2004-10-19 20:22 UTC (permalink / raw)
To: gcc-bugs
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 31364 bytes --]
Overall, the major problem is that the lhs operand object type, or most
optimal compatible type in the case of immedite operands, is not being
used to correcly select builtin functions; which is fairly important for
a compiler for 8-bit target to get right; where (u)divmod(q/h)i4 signed and
unsigned 8 and 16 bit builtin verions of the / and % functions corespondingly.
(This bug is independant of bug #10733, which doesn't actually seem
as a bug to me, unless the divmod built-in functions are coded incorrectly,
implies the use of divmodhi4 16 bit signed builtin; just as t1% = 30 implies
the use of the udivmodqi4 unsigned 8-bit builtin.
per ref: <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=10733> )
The following main.c and main.lss file listings demonstrate the failure:
// main.c
//
// inspecting code using avr-gcc 3.4.3 & buinutils 2.15.x as of 10/16/04 snapshots:
int main( void ){
volatile signed char s;
volatile unsigned char u;
//
// Overall, the major problem is that the lhs operand object type, or most
// optimal compatible type in the case of immedite operands, is not being
// used to correcly select builtin functions; which is fairly important for
// a compiler for 8-bit target to get right; where (u)divmod(q/h)i4 signed and
// unsigned 8 and 16 bit builtin verions of the / and % functions corespondingly.
//
// (This bug is independant of bug #10733, which doesn't actually seem
// as a bug to me, unless the divmod built-in functions are coded incorrectly,
// as in t1 = (t1 + 40) % 30; the (t1 + 40) sub-exp returns an int, which then
// implies the use of divmodhi4 16 bit signed builtin; just as t1% = 30 implies
// the use of the udivmodqi4 unsigned 8-bit builtin.
// per ref: <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=10733> )
char ss = s % s ; //<__divmodhi4> wrong, should be 8-bit <__divmodqi4>
char su = s % u ; //<__divmodhi4> correct.
char us = u % s ; //<__divmodhi4> correct.
char uu = u % u ; //<__udivmodqi4> correct.
// although optminally selecting the builtin's for rhs immediate's:
char sn = s % -3 ; //<__divmodqi4> correct.
char sp = s % +3 ; //<__divmodqi4> correct.
char un = u % -3 ; //<__divmodhi4> correct.
char up = u % +3 ; //<__udivmodqi4> correct.
// it never recognizes any opportunites for lhs immeidate's ?:
char ns = -3 % s ; //<__divmodhi4> wrong, should be 8-bit <__divmodqi4>
char ps = +3 % s ; //<__divmodhi4> wrong, should be 8-bit <__divmodqi4>
char nu = -3 % u ; //<__divmodhi4> wrong, should be 8-bit <__divmodqi4>
char pu = +3 % u ; //<__divmodhi4> wrong, should be 8-bit unsigned <__udivmodqi4>
// but does optimally select based on expicitly cast immediate values:
char uc = u % ( char)-3 ; //<__udivmodqi4> correct, :: unsigned char
char ux = u % ( signed char)-3 ; //<__divmodhi4> correct.
char uy = u % (unsigned char)-3 ; //<__udivmodqi4> correct.
char cu = ( char)-3 % u ; //<__udivmodqi4> correct, :: unsigned char
char xu = ( signed char)-3 % u ; //<__divmodhi4> correct.
char yu = (unsigned char)-3 % u ; //<__udivmodqi4> correct.
char sc = s % ( char)-3 ; //<__divmodhi4> correct, :: unsigned char
char sx = s % ( signed char)-3 ; //<__divmodqi4> correct.
char sy = s % (unsigned char)-3 ; //<__divmodhi4> correct.
char cs = ( char)-3 % s ; //<__divmodhi4> correct, :: unsigned char
char xs = ( signed char)-3 % s ; //<__divmodhi4> wrong, should be 8-bit <__divmodqi4>
char ys = (unsigned char)-3 % s ; //<__divmodhi4> correct.
return ss + su + us + uu +
sn + sp + un + up +
ns + ps + nu + pu +
uc + ux + uy + cu + xu + yu +
sc + sx + sy + cs + xs + ys ;
}
/*
main.lss file listing:
--begin--
main.elf: file format elf32-avr
Sections:
Idx Name Size VMA LMA File off Algn
0 .data 00000000 00800100 0000034e 000003e2 2**0
CONTENTS, ALLOC, LOAD, DATA
1 .text 0000034e 00000000 00000000 00000094 2**0
CONTENTS, ALLOC, LOAD, READONLY, CODE
2 .bss 00000000 00800100 0000034e 000003e2 2**0
ALLOC
3 .noinit 00000000 00800100 00800100 000003e2 2**0
CONTENTS
4 .eeprom 00000000 00810000 00810000 000003e2 2**0
CONTENTS
5 .stab 00000600 00000000 00000000 000003e4 2**2
CONTENTS, READONLY, DEBUGGING
6 .stabstr 000004c6 00000000 00000000 000009e4 2**0
CONTENTS, READONLY, DEBUGGING
Disassembly of section .text:
00000000 <__vectors>:
0: 0c 94 46 00 jmp 0x8c
4: 0c 94 61 00 jmp 0xc2
8: 0c 94 61 00 jmp 0xc2
c: 0c 94 61 00 jmp 0xc2
10: 0c 94 61 00 jmp 0xc2
14: 0c 94 61 00 jmp 0xc2
18: 0c 94 61 00 jmp 0xc2
1c: 0c 94 61 00 jmp 0xc2
20: 0c 94 61 00 jmp 0xc2
24: 0c 94 61 00 jmp 0xc2
28: 0c 94 61 00 jmp 0xc2
2c: 0c 94 61 00 jmp 0xc2
30: 0c 94 61 00 jmp 0xc2
34: 0c 94 61 00 jmp 0xc2
38: 0c 94 61 00 jmp 0xc2
3c: 0c 94 61 00 jmp 0xc2
40: 0c 94 61 00 jmp 0xc2
44: 0c 94 61 00 jmp 0xc2
48: 0c 94 61 00 jmp 0xc2
4c: 0c 94 61 00 jmp 0xc2
50: 0c 94 61 00 jmp 0xc2
54: 0c 94 61 00 jmp 0xc2
58: 0c 94 61 00 jmp 0xc2
5c: 0c 94 61 00 jmp 0xc2
60: 0c 94 61 00 jmp 0xc2
64: 0c 94 61 00 jmp 0xc2
68: 0c 94 61 00 jmp 0xc2
6c: 0c 94 61 00 jmp 0xc2
70: 0c 94 61 00 jmp 0xc2
74: 0c 94 61 00 jmp 0xc2
78: 0c 94 61 00 jmp 0xc2
7c: 0c 94 61 00 jmp 0xc2
80: 0c 94 61 00 jmp 0xc2
84: 0c 94 61 00 jmp 0xc2
88: 0c 94 61 00 jmp 0xc2
0000008c <__ctors_end>:
8c: 11 24 eor r1, r1
8e: 1f be out 0x3f, r1 ; 63
90: cf ef ldi r28, 0xFF ; 255
92: d0 e1 ldi r29, 0x10 ; 16
94: de bf out 0x3e, r29 ; 62
96: cd bf out 0x3d, r28 ; 61
00000098 <__do_copy_data>:
98: 11 e0 ldi r17, 0x01 ; 1
9a: a0 e0 ldi r26, 0x00 ; 0
9c: b1 e0 ldi r27, 0x01 ; 1
9e: ee e4 ldi r30, 0x4E ; 78
a0: f3 e0 ldi r31, 0x03 ; 3
a2: 02 c0 rjmp .+4 ; 0xa8
000000a4 <.do_copy_data_loop>:
a4: 05 90 lpm r0, Z+
a6: 0d 92 st X+, r0
000000a8 <.do_copy_data_start>:
a8: a0 30 cpi r26, 0x00 ; 0
aa: b1 07 cpc r27, r17
ac: d9 f7 brne .-10 ; 0xa4
000000ae <__do_clear_bss>:
ae: 11 e0 ldi r17, 0x01 ; 1
b0: a0 e0 ldi r26, 0x00 ; 0
b2: b1 e0 ldi r27, 0x01 ; 1
b4: 01 c0 rjmp .+2 ; 0xb8
000000b6 <.do_clear_bss_loop>:
b6: 1d 92 st X+, r1
000000b8 <.do_clear_bss_start>:
b8: a0 30 cpi r26, 0x00 ; 0
ba: b1 07 cpc r27, r17
bc: e1 f7 brne .-8 ; 0xb6
be: 0c 94 63 00 jmp 0xc6
000000c2 <__bad_interrupt>:
c2: 0c 94 00 00 jmp 0x0
000000c6 <main>:
// inspecting code using avr-gcc 3.4.3 & buinutils 2.15.x as of 10/16/04 snapshots:
int main( void ){
c6: c5 ef ldi r28, 0xF5 ; 245
c8: d0 e1 ldi r29, 0x10 ; 16
ca: de bf out 0x3e, r29 ; 62
cc: cd bf out 0x3d, r28 ; 61
volatile signed char s;
volatile unsigned char u;
//
// Overall, the major problem is that the lhs operand object type, or most
// optimal compatible type in the case of immedite operands, is not being
// used to correcly select builtin functions; which is fairly important for
// a compiler for 8-bit target to get right; where (u)divmod(q/h)i4 signed and
// unsigned 8 and 16 bit builtin verions of the / and % functions corespondingly.
//
// (this bug is independant of bug #10733, which doesn't actually seem
// as a bug to me, as in t1 = (t1 + 40) % 30; the (t1 + 40) sub-exp
// returns an int, which then implies the use of divmodhi4 16 bit signed
// builtin; just as t1% = 30 implies the use of the udivmodqi4 unsigned 8-bit
// builtin. ref: <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=10733> )
char ss = s % s ; //<__divmodhi4> wrong, should be 8-bit <__divmodqi4>
ce: 99 81 ldd r25, Y+1 ; 0x01
d0: 89 81 ldd r24, Y+1 ; 0x01
d2: 28 2f mov r18, r24
d4: 33 27 eor r19, r19
d6: 27 fd sbrc r18, 7
d8: 30 95 com r19
da: 89 2f mov r24, r25
dc: 99 27 eor r25, r25
de: 87 fd sbrc r24, 7
e0: 90 95 com r25
e2: b9 01 movw r22, r18
e4: 0e 94 7f 01 call 0x2fe
e8: 8b 83 std Y+3, r24 ; 0x03
char su = s % u ; //<__divmodhi4> correct.
ea: 99 81 ldd r25, Y+1 ; 0x01
ec: 8a 81 ldd r24, Y+2 ; 0x02
ee: 28 2f mov r18, r24
f0: 33 27 eor r19, r19
f2: 89 2f mov r24, r25
f4: 99 27 eor r25, r25
f6: 87 fd sbrc r24, 7
f8: 90 95 com r25
fa: b9 01 movw r22, r18
fc: 0e 94 7f 01 call 0x2fe
100: 8c 83 std Y+4, r24 ; 0x04
char us = u % s ; //<__divmodhi4> correct.
102: 9a 81 ldd r25, Y+2 ; 0x02
104: 89 81 ldd r24, Y+1 ; 0x01
106: 28 2f mov r18, r24
108: 33 27 eor r19, r19
10a: 27 fd sbrc r18, 7
10c: 30 95 com r19
10e: 89 2f mov r24, r25
110: 99 27 eor r25, r25
112: b9 01 movw r22, r18
114: 0e 94 7f 01 call 0x2fe
118: 8d 83 std Y+5, r24 ; 0x05
char uu = u % u ; //<__udivmodqi4> correct.
11a: 8a 81 ldd r24, Y+2 ; 0x02
11c: 9a 81 ldd r25, Y+2 ; 0x02
11e: 69 2f mov r22, r25
120: 0e 94 66 01 call 0x2cc
124: 9e 83 std Y+6, r25 ; 0x06
// although optminally selecting the builtin's for rhs immediate's:
char sn = s % -3 ; //<__divmodqi4> correct.
126: 89 81 ldd r24, Y+1 ; 0x01
128: 93 e0 ldi r25, 0x03 ; 3
12a: f9 2e mov r15, r25
12c: 6f 2d mov r22, r15
12e: 0e 94 72 01 call 0x2e4
132: 9f 83 std Y+7, r25 ; 0x07
char sp = s % +3 ; //<__divmodqi4> correct.
134: 89 81 ldd r24, Y+1 ; 0x01
136: 6f 2d mov r22, r15
138: 0e 94 72 01 call 0x2e4
13c: 98 87 std Y+8, r25 ; 0x08
char un = u % -3 ; //<__divmodhi4> correct.
13e: 8a 81 ldd r24, Y+2 ; 0x02
140: e3 e0 ldi r30, 0x03 ; 3
142: f0 e0 ldi r31, 0x00 ; 0
144: 99 27 eor r25, r25
146: bf 01 movw r22, r30
148: 0e 94 7f 01 call 0x2fe
14c: 89 87 std Y+9, r24 ; 0x09
char up = u % +3 ; //<__udivmodqi4> correct.
14e: 8a 81 ldd r24, Y+2 ; 0x02
150: 6f 2d mov r22, r15
152: 0e 94 66 01 call 0x2cc
156: 9a 87 std Y+10, r25 ; 0x0a
// it never recognizes any opportunites for lhs immeidate's ?:
char ns = -3 % s ; //<__divmodhi4> wrong, should be 8-bit <__divmodqi4>
158: 89 81 ldd r24, Y+1 ; 0x01
15a: 28 2f mov r18, r24
15c: 33 27 eor r19, r19
15e: 27 fd sbrc r18, 7
160: 30 95 com r19
162: 0d ef ldi r16, 0xFD ; 253
164: 1f ef ldi r17, 0xFF ; 255
166: c8 01 movw r24, r16
168: b9 01 movw r22, r18
16a: 0e 94 7f 01 call 0x2fe
16e: 28 2e mov r2, r24
char ps = +3 % s ; //<__divmodhi4> wrong, should be 8-bit <__divmodqi4>
170: 89 81 ldd r24, Y+1 ; 0x01
172: 28 2f mov r18, r24
174: 33 27 eor r19, r19
176: 27 fd sbrc r18, 7
178: 30 95 com r19
17a: cf 01 movw r24, r30
17c: b9 01 movw r22, r18
17e: 0e 94 7f 01 call 0x2fe
182: 38 2e mov r3, r24
char nu = -3 % u ; //<__divmodhi4> wrong, should be 8-bit <__divmodqi4>
184: 8a 81 ldd r24, Y+2 ; 0x02
186: 28 2f mov r18, r24
188: 33 27 eor r19, r19
18a: c8 01 movw r24, r16
18c: b9 01 movw r22, r18
18e: 0e 94 7f 01 call 0x2fe
192: 48 2e mov r4, r24
char pu = +3 % u ; //<__divmodhi4> wrong, should be 8-bit unsigned <__udivmodqi4>
194: 8a 81 ldd r24, Y+2 ; 0x02
196: 28 2f mov r18, r24
198: 33 27 eor r19, r19
19a: cf 01 movw r24, r30
19c: b9 01 movw r22, r18
19e: 0e 94 7f 01 call 0x2fe
1a2: 58 2e mov r5, r24
// but does optimally select based on expicitly cast immediate values:
char uc = u % ( char)-3 ; //<__udivmodqi4> correct, :: unsigned char
1a4: 8a 81 ldd r24, Y+2 ; 0x02
1a6: 4d ef ldi r20, 0xFD ; 253
1a8: 64 2f mov r22, r20
1aa: 0e 94 66 01 call 0x2cc
1ae: 69 2e mov r6, r25
char ux = u % ( signed char)-3 ; //<__divmodhi4> correct.
1b0: 8a 81 ldd r24, Y+2 ; 0x02
1b2: 99 27 eor r25, r25
1b4: bf 01 movw r22, r30
1b6: 0e 94 7f 01 call 0x2fe
1ba: 78 2e mov r7, r24
char uy = u % (unsigned char)-3 ; //<__udivmodqi4> correct.
1bc: 8a 81 ldd r24, Y+2 ; 0x02
1be: 64 2f mov r22, r20
1c0: 0e 94 66 01 call 0x2cc
1c4: 89 2e mov r8, r25
char cu = ( char)-3 % u ; //<__udivmodqi4> correct, :: unsigned char
1c6: 9a 81 ldd r25, Y+2 ; 0x02
1c8: 84 2f mov r24, r20
1ca: 69 2f mov r22, r25
1cc: 0e 94 66 01 call 0x2cc
1d0: 99 2e mov r9, r25
char xu = ( signed char)-3 % u ; //<__divmodhi4> correct.
1d2: 8a 81 ldd r24, Y+2 ; 0x02
1d4: 28 2f mov r18, r24
1d6: 33 27 eor r19, r19
1d8: c8 01 movw r24, r16
1da: b9 01 movw r22, r18
1dc: 0e 94 7f 01 call 0x2fe
1e0: a8 2e mov r10, r24
char yu = (unsigned char)-3 % u ; //<__udivmodqi4> correct.
1e2: 9a 81 ldd r25, Y+2 ; 0x02
1e4: 84 2f mov r24, r20
1e6: 69 2f mov r22, r25
1e8: 0e 94 66 01 call 0x2cc
1ec: b9 2e mov r11, r25
char sc = s % ( char)-3 ; //<__divmodhi4> correct, :: unsigned char
1ee: 89 81 ldd r24, Y+1 ; 0x01
1f0: ed ef ldi r30, 0xFD ; 253
1f2: f0 e0 ldi r31, 0x00 ; 0
1f4: 99 27 eor r25, r25
1f6: 87 fd sbrc r24, 7
1f8: 90 95 com r25
1fa: bf 01 movw r22, r30
1fc: 0e 94 7f 01 call 0x2fe
200: c8 2e mov r12, r24
char sx = s % ( signed char)-3 ; //<__divmodqi4> correct.
202: 89 81 ldd r24, Y+1 ; 0x01
204: 6f 2d mov r22, r15
206: 0e 94 72 01 call 0x2e4
20a: d9 2e mov r13, r25
char sy = s % (unsigned char)-3 ; //<__divmodhi4> correct.
20c: 89 81 ldd r24, Y+1 ; 0x01
20e: 99 27 eor r25, r25
210: 87 fd sbrc r24, 7
212: 90 95 com r25
214: bf 01 movw r22, r30
216: 0e 94 7f 01 call 0x2fe
21a: e8 2e mov r14, r24
char cs = ( char)-3 % s ; //<__divmodhi4> correct, :: unsigned char
21c: 89 81 ldd r24, Y+1 ; 0x01
21e: 28 2f mov r18, r24
220: 33 27 eor r19, r19
222: 27 fd sbrc r18, 7
224: 30 95 com r19
226: cf 01 movw r24, r30
228: b9 01 movw r22, r18
22a: 0e 94 7f 01 call 0x2fe
22e: f8 2e mov r15, r24
char xs = ( signed char)-3 % s ; //<__divmodhi4> wrong, should be 8-bit <__divmodqi4>
230: 89 81 ldd r24, Y+1 ; 0x01
232: 28 2f mov r18, r24
234: 33 27 eor r19, r19
236: 27 fd sbrc r18, 7
238: 30 95 com r19
23a: c8 01 movw r24, r16
23c: b9 01 movw r22, r18
23e: 0e 94 7f 01 call 0x2fe
242: 48 2f mov r20, r24
char ys = (unsigned char)-3 % s ; //<__divmodhi4> correct.
244: 89 81 ldd r24, Y+1 ; 0x01
246: 28 2f mov r18, r24
248: 33 27 eor r19, r19
24a: 27 fd sbrc r18, 7
24c: 30 95 com r19
24e: cf 01 movw r24, r30
250: b9 01 movw r22, r18
252: 0e 94 7f 01 call 0x2fe
return ss + su + us + uu +
256: 6b 81 ldd r22, Y+3 ; 0x03
258: 9c 81 ldd r25, Y+4 ; 0x04
25a: 69 0f add r22, r25
25c: 71 2d mov r23, r1
25e: 71 1d adc r23, r1
260: 9b 01 movw r18, r22
262: 6d 81 ldd r22, Y+5 ; 0x05
264: 26 0f add r18, r22
266: 31 1d adc r19, r1
268: 7e 81 ldd r23, Y+6 ; 0x06
26a: 27 0f add r18, r23
26c: 31 1d adc r19, r1
26e: 9f 81 ldd r25, Y+7 ; 0x07
270: 29 0f add r18, r25
272: 31 1d adc r19, r1
274: 68 85 ldd r22, Y+8 ; 0x08
276: 26 0f add r18, r22
278: 31 1d adc r19, r1
27a: 79 85 ldd r23, Y+9 ; 0x09
27c: 27 0f add r18, r23
27e: 31 1d adc r19, r1
280: 9a 85 ldd r25, Y+10 ; 0x0a
282: 29 0f add r18, r25
284: 31 1d adc r19, r1
286: 22 0d add r18, r2
288: 31 1d adc r19, r1
28a: 23 0d add r18, r3
28c: 31 1d adc r19, r1
28e: 24 0d add r18, r4
290: 31 1d adc r19, r1
292: 25 0d add r18, r5
294: 31 1d adc r19, r1
296: 26 0d add r18, r6
298: 31 1d adc r19, r1
29a: 27 0d add r18, r7
29c: 31 1d adc r19, r1
29e: 28 0d add r18, r8
2a0: 31 1d adc r19, r1
2a2: 29 0d add r18, r9
2a4: 31 1d adc r19, r1
2a6: 2a 0d add r18, r10
2a8: 31 1d adc r19, r1
2aa: 2b 0d add r18, r11
2ac: 31 1d adc r19, r1
2ae: 2c 0d add r18, r12
2b0: 31 1d adc r19, r1
2b2: 2d 0d add r18, r13
2b4: 31 1d adc r19, r1
2b6: 2e 0d add r18, r14
2b8: 31 1d adc r19, r1
2ba: 2f 0d add r18, r15
2bc: 31 1d adc r19, r1
2be: 24 0f add r18, r20
2c0: 31 1d adc r19, r1
sn + sp + un + up +
ns + ps + nu + pu +
uc + ux + uy + cu + xu + yu +
sc + sx + sy + cs + xs + ys ;
}
2c2: 28 0f add r18, r24
2c4: 31 1d adc r19, r1
2c6: c9 01 movw r24, r18
2c8: 0c 94 a6 01 jmp 0x34c
000002cc <__udivmodqi4>:
2cc: 99 1b sub r25, r25
2ce: 79 e0 ldi r23, 0x09 ; 9
2d0: 04 c0 rjmp .+8 ; 0x2da
000002d2 <__udivmodqi4_loop>:
2d2: 99 1f adc r25, r25
2d4: 96 17 cp r25, r22
2d6: 08 f0 brcs .+2 ; 0x2da
2d8: 96 1b sub r25, r22
000002da <__udivmodqi4_ep>:
2da: 88 1f adc r24, r24
2dc: 7a 95 dec r23
2de: c9 f7 brne .-14 ; 0x2d2
2e0: 80 95 com r24
2e2: 08 95 ret
000002e4 <__divmodqi4>:
2e4: 87 fb bst r24, 7
2e6: 08 2e mov r0, r24
2e8: 06 26 eor r0, r22
2ea: 87 fd sbrc r24, 7
2ec: 81 95 neg r24
2ee: 67 fd sbrc r22, 7
2f0: 61 95 neg r22
2f2: ec df rcall .-40 ; 0x2cc
2f4: 0e f4 brtc .+2 ; 0x2f8
2f6: 91 95 neg r25
000002f8 <__divmodqi4_1>:
2f8: 07 fc sbrc r0, 7
2fa: 81 95 neg r24
000002fc <__divmodqi4_exit>:
2fc: 08 95 ret
000002fe <__divmodhi4>:
2fe: 97 fb bst r25, 7
300: 09 2e mov r0, r25
302: 07 26 eor r0, r23
304: 0a d0 rcall .+20 ; 0x31a
306: 77 fd sbrc r23, 7
308: 04 d0 rcall .+8 ; 0x312
30a: 0c d0 rcall .+24 ; 0x324
30c: 06 d0 rcall .+12 ; 0x31a
30e: 00 20 and r0, r0
310: 1a f4 brpl .+6 ; 0x318
00000312 <__divmodhi4_neg2>:
312: 70 95 com r23
314: 61 95 neg r22
316: 7f 4f sbci r23, 0xFF ; 255
00000318 <__divmodhi4_exit>:
318: 08 95 ret
0000031a <__divmodhi4_neg1>:
31a: f6 f7 brtc .-4 ; 0x318
31c: 90 95 com r25
31e: 81 95 neg r24
320: 9f 4f sbci r25, 0xFF ; 255
322: 08 95 ret
00000324 <__udivmodhi4>:
324: aa 1b sub r26, r26
326: bb 1b sub r27, r27
328: 51 e1 ldi r21, 0x11 ; 17
32a: 07 c0 rjmp .+14 ; 0x33a
0000032c <__udivmodhi4_loop>:
32c: aa 1f adc r26, r26
32e: bb 1f adc r27, r27
330: a6 17 cp r26, r22
332: b7 07 cpc r27, r23
334: 10 f0 brcs .+4 ; 0x33a
336: a6 1b sub r26, r22
338: b7 0b sbc r27, r23
0000033a <__udivmodhi4_ep>:
33a: 88 1f adc r24, r24
33c: 99 1f adc r25, r25
33e: 5a 95 dec r21
340: a9 f7 brne .-22 ; 0x32c
342: 80 95 com r24
344: 90 95 com r25
346: bc 01 movw r22, r24
348: cd 01 movw r24, r26
34a: 08 95 ret
0000034c <_exit>:
34c: ff cf rjmp .-2 ; 0x34c
---end---
makefile file listing:
--begin--
# Hey Emacs, this is a -*- makefile -*-
#
# WinAVR Sample makefile written by Eric B. Weddington, JËrg Wunsch, et al.
# Released to the Public Domain
# Please read the make user manual!
#
# Additional material for this makefile was submitted by:
# Tim Henigan
# Peter Fleury
# Reiner Patommel
# Sander Pool
# Frederik Rouleau
# Markus Pfaff
#
# On command line:
#
# make all = Make software.
#
# make clean = Clean out built project files.
#
# make coff = Convert ELF to AVR COFF (for use with AVR Studio 3.x or VMLAB).
#
# make extcoff = Convert ELF to AVR Extended COFF (for use with AVR Studio
# 4.07 or greater).
#
# make program = Download the hex file to the device, using avrdude. Please
# customize the avrdude settings below first!
#
# make filename.s = Just compile filename.c into the assembler code only
#
# To rebuild project do "make clean" then "make all".
#
# MCU name
MCU = atmega64
# Output format. (can be srec, ihex, binary)
FORMAT = ihex
# Target file name (without extension).
TARGET = main
# List C source files here. (C dependencies are automatically generated.)
SRC = $(TARGET).c
# List Assembler source files here.
# Make them always end in a capital .S. Files ending in a lowercase .s
# will not be considered source files but generated files (assembler
# output from the compiler), and will be deleted upon "make clean"!
# Even though the DOS/Win* filesystem matches both .s and .S the same,
# it will preserve the spelling of the filenames, and gcc itself does
# care about how the name is spelled on its command-line.
ASRC =
# Optimization level, can be [0, 1, 2, 3, s].
# 0 = turn off optimization. s = optimize for size.
# (Note: 3 is not always the best optimization level. See avr-libc FAQ.)
OPT = s
# Debugging format.
# Native formats for AVR-GCC's -g are stabs [default], or dwarf-2.
# AVR (extended) COFF requires stabs, plus an avr-objcopy run.
#DEBUG = dwarf-2
DEBUG =
# List any extra directories to look for include files here.
# Each directory must be seperated by a space.
EXTRAINCDIRS = /usr/local/avr/include
# Compiler flag to set the C Standard level.
# c89 - "ANSI" C
# gnu89 - c89 plus GCC extensions
# c99 - ISO C99 standard (not yet fully implemented)
# gnu99 - c99 plus GCC extensions
CSTANDARD = -std=gnu99
# Place -D or -U options here
CDEFS =
# Place -I options here
CINCS =
# Compiler flags.
# -g*: generate debugging information
# -O*: optimization level
# -f...: tuning, see GCC manual and avr-libc documentation
# -Wall...: warning level
# -Wa,...: tell GCC to pass this to the assembler.
# -adhlns...: create assembler listing
CFLAGS = -g$(DEBUG)
CFLAGS += $(CDEFS) $(CINCS)
CFLAGS += -O$(OPT)
CFLAGS += -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums
CFLAGS += -Wall -Wstrict-prototypes
CFLAGS += -Wa,-adhlns=$(<:.c=.lst)
CFLAGS += $(patsubst %,-I%,$(EXTRAINCDIRS))
CFLAGS += $(CSTANDARD)
# Assembler flags.
# -Wa,...: tell GCC to pass this to the assembler.
# -ahlms: create listing
# -gstabs: have the assembler create line number information; note that
# for use in COFF files, additional information about filenames
# and function names needs to be present in the assembler source
# files -- see avr-libc docs [FIXME: not yet described there]
ASFLAGS = -Wa,-adhlns=$(<:.S=.lst),-gstabs
#Additional libraries.
# Minimalistic printf version
PRINTF_LIB_MIN = -Wl,-u,vfprintf -lprintf_min
# Floating point printf version (requires MATH_LIB = -lm below)
PRINTF_LIB_FLOAT = -Wl,-u,vfprintf -lprintf_flt
PRINTF_LIB =
# Minimalistic scanf version
SCANF_LIB_MIN = -Wl,-u,vfscanf -lscanf_min
# Floating point + %[ scanf version (requires MATH_LIB = -lm below)
SCANF_LIB_FLOAT = -Wl,-u,vfscanf -lscanf_flt
SCANF_LIB =
MATH_LIB = -lm
# External memory options
# 64 KB of external RAM, starting after internal RAM (ATmega128!),
# used for variables (.data/.bss) and heap (malloc()).
#EXTMEMOPTS = -Wl,-Tdata=0x801100,--defsym=__heap_end=0x80ffff
# 64 KB of external RAM, starting after internal RAM (ATmega128!),
# only used for heap (malloc()).
#EXTMEMOPTS = -Wl,--defsym=__heap_start=0x801100,--defsym=__heap_end=0x80ffff
EXTMEMOPTS =
# Linker flags.
# -Wl,...: tell GCC to pass this to linker.
# -Map: create map file
# --cref: add cross reference to map file
LDFLAGS = -Wl,-Map=$(TARGET).map,--cref
LDFLAGS += $(EXTMEMOPTS)
LDFLAGS += $(PRINTF_LIB) $(SCANF_LIB) $(MATH_LIB)
# Programming support using avrdude. Settings and variables.
# Programming hardware: alf avr910 avrisp bascom bsd
# dt006 pavr picoweb pony-stk200 sp12 stk200 stk500
#
# Type: avrdude -c ?
# to get a full listing.
#
AVRDUDE_PROGRAMMER = stk500
# com1 = serial port. Use lpt1 to connect to parallel port.
AVRDUDE_PORT = com1 # programmer connected to serial device
AVRDUDE_WRITE_FLASH = -U flash:w:$(TARGET).hex
#AVRDUDE_WRITE_EEPROM = -U eeprom:w:$(TARGET).eep
# Uncomment the following if you want avrdude's erase cycle counter.
# Note that this counter needs to be initialized first using -Yn,
# see avrdude manual.
#AVRDUDE_ERASE_COUNTER = -y
# Uncomment the following if you do /not/ wish a verification to be
# performed after programming the device.
#AVRDUDE_NO_VERIFY = -V
# Increase verbosity level. Please use this when submitting bug
# reports about avrdude. See <http://savannah.nongnu.org/projects/avrdude>
# to submit bug reports.
#AVRDUDE_VERBOSE = -v -v
AVRDUDE_FLAGS = -p $(MCU) -P $(AVRDUDE_PORT) -c $(AVRDUDE_PROGRAMMER)
AVRDUDE_FLAGS += $(AVRDUDE_NO_VERIFY)
AVRDUDE_FLAGS += $(AVRDUDE_VERBOSE)
AVRDUDE_FLAGS += $(AVRDUDE_ERASE_COUNTER)
# ---------------------------------------------------------------------------
# Define directories, if needed.
#DIRAVR = c:/winavr
#DIRAVRBIN = $(DIRAVR)/bin
#DIRAVRUTILS = $(DIRAVR)/utils/bin
#DIRINC = .
#DIRLIB = $(DIRAVR)/avr/lib
# Define programs and commands.
SHELL = sh
CC = avr-gcc
OBJCOPY = avr-objcopy
OBJDUMP = avr-objdump
SIZE = avr-size
NM = avr-nm
AVRDUDE = avrdude
REMOVE = rm -f
COPY = cp
# Define Messages
# English
MSG_ERRORS_NONE = Errors: none
MSG_BEGIN = -------- begin --------
MSG_END = -------- end --------
MSG_SIZE_BEFORE = Size before:
MSG_SIZE_AFTER = Size after:
MSG_COFF = Converting to AVR COFF:
MSG_EXTENDED_COFF = Converting to AVR Extended COFF:
MSG_FLASH = Creating load file for Flash:
MSG_EEPROM = Creating load file for EEPROM:
MSG_EXTENDED_LISTING = Creating Extended Listing:
MSG_SYMBOL_TABLE = Creating Symbol Table:
MSG_LINKING = Linking:
MSG_COMPILING = Compiling:
MSG_ASSEMBLING = Assembling:
MSG_CLEANING = Cleaning project:
# Define all object files.
OBJ = $(SRC:.c=.o) $(ASRC:.S=.o)
# Define all listing files.
LST = $(ASRC:.S=.lst) $(SRC:.c=.lst)
# Compiler flags to generate dependency files.
GENDEPFLAGS = -Wp,-M,-MP,-MT,$(*F).o,-MF,.dep/$(@F).d
# Combine all necessary flags and optional flags.
# Add target processor to flags.
ALL_CFLAGS = -mmcu=$(MCU) -I. $(CFLAGS) $(GENDEPFLAGS)
ALL_ASFLAGS = -mmcu=$(MCU) -I. -x assembler-with-cpp $(ASFLAGS)
# Default target.
all: begin gccversion sizebefore build sizeafter finished end
build: elf hex eep lss sym
elf: $(TARGET).elf
hex: $(TARGET).hex
eep: $(TARGET).eep
lss: $(TARGET).lss
sym: $(TARGET).sym
# Eye candy.
# AVR Studio 3.x does not check make's exit code but relies on
# the following magic strings to be generated by the compile job.
begin:
@echo
@echo $(MSG_BEGIN)
finished:
@echo $(MSG_ERRORS_NONE)
end:
@echo $(MSG_END)
@echo
# Display size of file.
HEXSIZE = $(SIZE) --target=$(FORMAT) $(TARGET).hex
ELFSIZE = $(SIZE) -A $(TARGET).elf
sizebefore:
@if [ -f $(TARGET).elf ]; then echo; echo $(MSG_SIZE_BEFORE); $(ELFSIZE); echo; fi
sizeafter:
@if [ -f $(TARGET).elf ]; then echo; echo $(MSG_SIZE_AFTER); $(ELFSIZE); echo; fi
# Display compiler version information.
gccversion :
@$(CC) --version
# Program the device.
#program: $(TARGET).hex $(TARGET).eep
# $(AVRDUDE) $(AVRDUDE_FLAGS) $(AVRDUDE_WRITE_FLASH) #$(AVRDUDE_WRITE_EEPROM)
# Convert ELF to COFF for use in debugging / simulating in AVR Studio or VMLAB.
COFFCONVERT=$(OBJCOPY) --debugging \
--change-section-address .data-0x800000 \
--change-section-address .bss-0x800000 \
--change-section-address .noinit-0x800000 \
--change-section-address .eeprom-0x810000
coff: $(TARGET).elf
@echo
@echo $(MSG_COFF) $(TARGET).cof
$(COFFCONVERT) -O coff-avr $< $(TARGET).cof
extcoff: $(TARGET).elf
@echo
@echo $(MSG_EXTENDED_COFF) $(TARGET).cof
$(COFFCONVERT) -O coff-ext-avr $< $(TARGET).cof
# Create final output files (.hex, .eep) from ELF output file.
%.hex: %.elf
@echo
@echo $(MSG_FLASH) $@
$(OBJCOPY) -O $(FORMAT) -R .eeprom $< $@
%.eep: %.elf
@echo
@echo $(MSG_EEPROM) $@
-$(OBJCOPY) -j .eeprom --set-section-flags=.eeprom="alloc,load" \
--change-section-lma .eeprom=0 -O $(FORMAT) $< $@
# Create extended listing file from ELF output file.
%.lss: %.elf
@echo
@echo $(MSG_EXTENDED_LISTING) $@
$(OBJDUMP) -h -S $< > $@
# Create a symbol table from ELF output file.
%.sym: %.elf
@echo
@echo $(MSG_SYMBOL_TABLE) $@
$(NM) -n $< > $@
# Link: create ELF output file from object files.
.SECONDARY : $(TARGET).elf
.PRECIOUS : $(OBJ)
%.elf: $(OBJ)
@echo
@echo $(MSG_LINKING) $@
$(CC) $(ALL_CFLAGS) $(OBJ) --output $@ $(LDFLAGS)
# Compile: create object files from C source files.
%.o : %.c
@echo
@echo $(MSG_COMPILING) $<
$(CC) -c $(ALL_CFLAGS) $< -o $@
# Compile: create assembler files from C source files.
%.s : %.c
$(CC) -S $(ALL_CFLAGS) $< -o $@
# Assemble: create object files from assembler source files.
%.o : %.S
@echo
@echo $(MSG_ASSEMBLING) $<
$(CC) -c $(ALL_ASFLAGS) $< -o $@
# Target: clean project.
clean: begin clean_list finished end
clean_list :
@echo
@echo $(MSG_CLEANING)
$(REMOVE) $(TARGET).hex
$(REMOVE) $(TARGET).eep
$(REMOVE) $(TARGET).obj
$(REMOVE) $(TARGET).cof
$(REMOVE) $(TARGET).elf
$(REMOVE) $(TARGET).map
$(REMOVE) $(TARGET).obj
$(REMOVE) $(TARGET).a90
$(REMOVE) $(TARGET).sym
$(REMOVE) $(TARGET).lnk
$(REMOVE) $(TARGET).lss
$(REMOVE) $(OBJ)
$(REMOVE) $(LST)
$(REMOVE) $(SRC:.c=.s)
$(REMOVE) $(SRC:.c=.d)
$(REMOVE) .dep/*
# Include the dependency files.
-include $(shell mkdir .dep 2>/dev/null) $(wildcard .dep/*)
# Listing of phony targets.
.PHONY : all begin finish end sizebefore sizeafter gccversion \
build elf hex eep lss sym coff extcoff \
clean clean_list
#clean clean_list program
---end---
*/
--
Summary: wrong built-in functions selected
Product: gcc
Version: 3.4.3
Status: UNCONFIRMED
Severity: critical
Priority: P1
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: schlie at comcast dot net
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: powerpc-apple-darwin7.5.0
GCC host triplet: powerpc-apple-darwin7.5.0
GCC target triplet: avr-unknown-none
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug c/18065] wrong built-in functions selected
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
@ 2004-10-19 20:27 ` schlie at comcast dot net
2004-10-19 20:39 ` [Bug target/18065] " pinskia at gcc dot gnu dot org
` (31 subsequent siblings)
32 siblings, 0 replies; 40+ messages in thread
From: schlie at comcast dot net @ 2004-10-19 20:27 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2004-10-19 20:27 -------
Created an attachment (id=7378)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=7378&action=view)
main.c (with embedded commented out main.lss and makefile)
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug target/18065] wrong built-in functions selected
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
2004-10-19 20:27 ` [Bug c/18065] " schlie at comcast dot net
@ 2004-10-19 20:39 ` pinskia at gcc dot gnu dot org
2004-10-19 21:18 ` schlie at comcast dot net
` (30 subsequent siblings)
32 siblings, 0 replies; 40+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2004-10-19 20:39 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-19 20:39 -------
char ss = s % s ; //<__divmodhi4> wrong, should be 8-bit <__divmodqi4>
This is not wrong as we sign extend the arguments as required by the C standard (to int).
So this is just an missed-optimization.
--
What |Removed |Added
----------------------------------------------------------------------------
Severity|critical |minor
Component|c |target
Keywords| |missed-optimization
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug target/18065] wrong built-in functions selected
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
2004-10-19 20:27 ` [Bug c/18065] " schlie at comcast dot net
2004-10-19 20:39 ` [Bug target/18065] " pinskia at gcc dot gnu dot org
@ 2004-10-19 21:18 ` schlie at comcast dot net
2004-10-19 21:31 ` schlie at comcast dot net
` (29 subsequent siblings)
32 siblings, 0 replies; 40+ messages in thread
From: schlie at comcast dot net @ 2004-10-19 21:18 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2004-10-19 21:18 -------
Subject: Re: wrong built-in functions selected
Nope, please look at the coded examples:
- they demonstrate that:
(signed char) % (signed char) => invokes (int) % (int), not correct.
- and the compiler consistently treats rhs immediate value differently
than lhs immediate values for some non-descript reason? (arguably,
it should assume all immediate values are ints unless cast/specified
otherwise, but that's not what it does, nor does it properly treat
lhs operands as signed chars even if properly explicitly cast.
Thanks, -paul-
> From: pinskia at gcc dot gnu dot org <gcc-bugzilla@gcc.gnu.org>
> Reply-To: <gcc-bugzilla@gcc.gnu.org>
> Date: 19 Oct 2004 20:39:44 -0000
> To: <schlie@comcast.net>
> Subject: [Bug target/18065] wrong built-in functions selected
>
>
> ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-19
> 20:39 -------
> char ss = s % s ; //<__divmodhi4> wrong, should be 8-bit <__divmodqi4>
> This is not wrong as we sign extend the arguments as required by the C
> standard (to int).
>
> So this is just an missed-optimization.
>
> --
> What |Removed |Added
> ----------------------------------------------------------------------------
> Severity|critical |minor
> Component|c |target
> Keywords| |missed-optimization
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
>
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug target/18065] wrong built-in functions selected
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (2 preceding siblings ...)
2004-10-19 21:18 ` schlie at comcast dot net
@ 2004-10-19 21:31 ` schlie at comcast dot net
2004-10-19 21:39 ` [Bug target/18065] not using qi version of divmod pinskia at gcc dot gnu dot org
` (28 subsequent siblings)
32 siblings, 0 replies; 40+ messages in thread
From: schlie at comcast dot net @ 2004-10-19 21:31 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2004-10-19 21:31 -------
Subject: Re: wrong built-in functions selected
As of course otherwise then, what's the purpose of s/u 8-bit / and %
built-in functions, if not to enable their use when all the operands are
type compatible, minimally explicitly and ideally when type compatible?
-paul-
> From: schlie at comcast dot net <gcc-bugzilla@gcc.gnu.org>
> Reply-To: <gcc-bugzilla@gcc.gnu.org>
> Date: 19 Oct 2004 21:18:17 -0000
> To: <schlie@comcast.net>
> Subject: [Bug target/18065] wrong built-in functions selected
>
>
> ------- Additional Comments From schlie at comcast dot net 2004-10-19 21:18
> -------
> Subject: Re: wrong built-in functions selected
>
> Nope, please look at the coded examples:
>
> - they demonstrate that:
>
> (signed char) % (signed char) => invokes (int) % (int), not correct.
>
> - and the compiler consistently treats rhs immediate value differently
> than lhs immediate values for some non-descript reason? (arguably,
> it should assume all immediate values are ints unless cast/specified
> otherwise, but that's not what it does, nor does it properly treat
> lhs operands as signed chars even if properly explicitly cast.
>
> Thanks, -paul-
>
>> From: pinskia at gcc dot gnu dot org <gcc-bugzilla@gcc.gnu.org>
>> Reply-To: <gcc-bugzilla@gcc.gnu.org>
>> Date: 19 Oct 2004 20:39:44 -0000
>> To: <schlie@comcast.net>
>> Subject: [Bug target/18065] wrong built-in functions selected
>>
>>
>> ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-19
>> 20:39 -------
>> char ss = s % s ; //<__divmodhi4> wrong, should be 8-bit <__divmodqi4>
>> This is not wrong as we sign extend the arguments as required by the C
>> standard (to int).
>>
>> So this is just an missed-optimization.
>>
>> --
>> What |Removed |Added
>> ----------------------------------------------------------------------------
>> Severity|critical |minor
>> Component|c |target
>> Keywords| |missed-optimization
>>
>>
>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
>>
>> ------- You are receiving this mail because: -------
>> You reported the bug, or are watching the reporter.
>
>
>
>
> --
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
>
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug target/18065] not using qi version of divmod
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (3 preceding siblings ...)
2004-10-19 21:31 ` schlie at comcast dot net
@ 2004-10-19 21:39 ` pinskia at gcc dot gnu dot org
2004-10-19 21:53 ` schlie at comcast dot net
` (27 subsequent siblings)
32 siblings, 0 replies; 40+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2004-10-19 21:39 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-19 21:39 -------
I don't know but as I said this is correct code and not a wrong code problem but just a missed
optimization somewhere.
--
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever Confirmed| |1
GCC build triplet|powerpc-apple-darwin7.5.0 |
GCC host triplet|powerpc-apple-darwin7.5.0 |
Last reconfirmed|0000-00-00 00:00:00 |2004-10-19 21:39:26
date| |
Summary|wrong built-in functions |not using qi version of
|selected |divmod
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug target/18065] not using qi version of divmod
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (4 preceding siblings ...)
2004-10-19 21:39 ` [Bug target/18065] not using qi version of divmod pinskia at gcc dot gnu dot org
@ 2004-10-19 21:53 ` schlie at comcast dot net
2004-10-19 22:08 ` ericw at evcohs dot com
` (26 subsequent siblings)
32 siblings, 0 replies; 40+ messages in thread
From: schlie at comcast dot net @ 2004-10-19 21:53 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2004-10-19 21:53 -------
Subject: Re: not using qi version of divmod
I agree that the missed optimizations won't produce incorrect results, just
very inefficient ones. As all rhs argument optimizations seem to be properly
identified, and yet no lhs's are; it would imply to me that where ever in
gcc argument signatures are being computed or used for the purpose of
built-in function selection, it's inappropriately ignoring lhs argument
type compatibility; would you agree with that somewhat crude assessment?
Thanks again,-paul-
> From: pinskia at gcc dot gnu dot org <gcc-bugzilla@gcc.gnu.org>
> Reply-To: <gcc-bugzilla@gcc.gnu.org>
> Date: 19 Oct 2004 21:39:27 -0000
> To: <schlie@comcast.net>
> Subject: [Bug target/18065] not using qi version of divmod
>
>
> ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-19
> 21:39 -------
> I don't know but as I said this is correct code and not a wrong code problem
> but just a missed
> optimization somewhere.
>
> --
> What |Removed |Added
> ----------------------------------------------------------------------------
> Status|UNCONFIRMED |NEW
> Ever Confirmed| |1
> GCC build triplet|powerpc-apple-darwin7.5.0 |
> GCC host triplet|powerpc-apple-darwin7.5.0 |
> Last reconfirmed|0000-00-00 00:00:00 |2004-10-19 21:39:26
> date| |
> Summary|wrong built-in functions |not using qi version of
> |selected |divmod
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
>
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug target/18065] not using qi version of divmod
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (5 preceding siblings ...)
2004-10-19 21:53 ` schlie at comcast dot net
@ 2004-10-19 22:08 ` ericw at evcohs dot com
2004-10-19 22:31 ` schlie at comcast dot net
` (25 subsequent siblings)
32 siblings, 0 replies; 40+ messages in thread
From: ericw at evcohs dot com @ 2004-10-19 22:08 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From ericw at evcohs dot com 2004-10-19 22:08 -------
Bug #10733 is related.
--
What |Removed |Added
----------------------------------------------------------------------------
CC| |ericw at evcohs dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug target/18065] not using qi version of divmod
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
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2004-10-19 22:08 ` ericw at evcohs dot com
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From: schlie at comcast dot net @ 2004-10-19 22:31 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2004-10-19 22:31 -------
Subject: Re: not using qi version of divmod
Hi Eric,
Out of curiosity, what exactly is the 10733 bug, is wrong result computed?
If so, that implies that divmodhi is broken; otherwise it's not a bug, as
the intermediate (t1 + 40) expression yields an int result, as within the
context of the expression, although t1 is an unsigned char, there's no
guarantee that (t1 + 40) will not overflow an unsigned char size, therefore
properly assumed to be an int; unlike t1 = t1 % 3 or whatever, where all
operands are clearly type compatible with unsigned char, and a valid
optimization.
-paul-
> From: ericw at evcohs dot com <gcc-bugzilla@gcc.gnu.org>
> Reply-To: <gcc-bugzilla@gcc.gnu.org>
> Date: 19 Oct 2004 22:08:15 -0000
> To: <schlie@comcast.net>
> Subject: [Bug target/18065] not using qi version of divmod
>
>
> ------- Additional Comments From ericw at evcohs dot com 2004-10-19 22:08
> -------
> Bug #10733 is related.
>
> --
> What |Removed |Added
> ----------------------------------------------------------------------------
> CC| |ericw at evcohs dot com
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
>
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
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* [Bug target/18065] not using qi version of divmod
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (7 preceding siblings ...)
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From: ericw at evcohs dot com @ 2004-10-19 23:13 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From ericw at evcohs dot com 2004-10-19 23:13 -------
Subject: Re: not using qi version of divmod
schlie at comcast dot net wrote:
>------- Additional Comments From schlie at comcast dot net 2004-10-19 22:31 -------
>Subject: Re: not using qi version of divmod
>
>Hi Eric,
>
>Out of curiosity, what exactly is the 10733 bug, is wrong result computed?
>
>If so, that implies that divmodhi is broken; otherwise it's not a bug, as
>the intermediate (t1 + 40) expression yields an int result, as within the
>context of the expression, although t1 is an unsigned char, there's no
>guarantee that (t1 + 40) will not overflow an unsigned char size, therefore
>properly assumed to be an int; unlike t1 = t1 % 3 or whatever, where all
>operands are clearly type compatible with unsigned char, and a valid
>optimization.
>
>
Bug #10733 is a wrong-code bug involving the modulus operator on the AVR
target. See the bug report itself for more information.
Eric
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug target/18065] not using qi version of divmod
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (8 preceding siblings ...)
2004-10-19 23:13 ` ericw at evcohs dot com
@ 2004-10-20 18:34 ` schlie at comcast dot net
2004-10-20 18:50 ` [Bug c/18065] usual arithmetic conversion not applying correctly pinskia at gcc dot gnu dot org
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From: schlie at comcast dot net @ 2004-10-20 18:34 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2004-10-20 18:34 -------
Subject: Re: wrong code emitted
Hi Andrew,
Please correct the failure mode description to " critical, wrong code",
as upon reviewing the avr.md file, it's now clear that this isn't a
"missed optimization"; GCC is failing to properly emit the instruction
explicitly matching it's specified QI mode operand constraints as specified
by a corresponding identically constrained C statement; more specifically:
(this behavior should be deterministic, and relies on no optimizations)
The explicit C declaration statement (which also fails for %):
signed char ss = (signed char)s / (signed char)s ;
Incorrectly emits an HI vs. QI mode instruction as specified avr.md
//uses <__divmodhi4> wrong, should be 8-bit <__divmodqi4>
ce: 99 81 ldd r25, Y+1 ; 0x01
d0: 89 81 ldd r24, Y+1 ; 0x01
d2: 28 2f mov r18, r24
d4: 33 27 eor r19, r19
d6: 27 fd sbrc r18, 7
d8: 30 95 com r19
da: 89 2f mov r24, r25
dc: 99 27 eor r25, r25
de: 87 fd sbrc r24, 7
e0: 90 95 com r25
e2: b9 01 movw r22, r18
e4: 0e 94 81 01 call __divmodhi4
e8: 6b 83 std Y+3, r22 ; 0x03
Where the corresponding avr.md specifications are:
(define_expand "divmodqi4"
[(set (reg:QI 24) (match_operand:QI 1 "register_operand" ""))
(set (reg:QI 22) (match_operand:QI 2 "register_operand" ""))
(parallel [(set (reg:QI 24) (div:QI (reg:QI 24) (reg:QI 22)))
(set (reg:QI 25) (mod:QI (reg:QI 24) (reg:QI 22)))
(clobber (reg:QI 22))
(clobber (reg:QI 23))])
(set (match_operand:QI 0 "register_operand" "") (reg:QI 24))
(set (match_operand:QI 3 "register_operand" "") (reg:QI 25))]
""
"")
(define_insn "*divmodqi4_call"
[(set (reg:QI 24) (div:QI (reg:QI 24) (reg:QI 22)))
(set (reg:QI 25) (mod:QI (reg:QI 24) (reg:QI 22)))
(clobber (reg:QI 22))
(clobber (reg:QI 23))]
""
"%~call __divmodqi4"
[(set_attr "type" "xcall")
(set_attr "cc" "clobber")])
(define_expand "divmodhi4"
[(set (reg:HI 24) (match_operand:HI 1 "register_operand" ""))
(set (reg:HI 22) (match_operand:HI 2 "register_operand" ""))
(parallel [(set (reg:HI 22) (div:HI (reg:HI 24) (reg:HI 22)))
(set (reg:HI 24) (mod:HI (reg:HI 24) (reg:HI 22)))
(clobber (reg:HI 26))
(clobber (reg:QI 21))])
(set (match_operand:HI 0 "register_operand" "") (reg:HI 22))
(set (match_operand:HI 3 "register_operand" "") (reg:HI 24))]
""
"")
(define_insn "*divmodhi4_call"
[(set (reg:HI 22) (div:HI (reg:HI 24) (reg:HI 22)))
(set (reg:HI 24) (mod:HI (reg:HI 24) (reg:HI 22)))
(clobber (reg:HI 26))
(clobber (reg:QI 21))]
""
"%~call __divmodhi4"
[(set_attr "type" "xcall")
(set_attr "cc" "clobber")])
Which seems correct, but for some reason GCC is not able to recognize
when it's lhs operand is a QI mode operand when attempting to match
this specification when emitting code?
Thanks again, -paul-
> From: pinskia at gcc dot gnu dot org <gcc-bugzilla@gcc.gnu.org>
> Reply-To: <gcc-bugzilla@gcc.gnu.org>
> Date: 19 Oct 2004 20:39:44 -0000
> To: <schlie@comcast.net>
> Subject: [Bug target/18065] wrong built-in functions selected
>
>
> ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-19
> 20:39 -------
> char ss = s % s ; //<__divmodhi4> wrong, should be 8-bit <__divmodqi4>
> This is not wrong as we sign extend the arguments as required by the C
> standard (to int).
>
> So this is just an missed-optimization.
>
> --
> What |Removed |Added
> ----------------------------------------------------------------------------
> Severity|critical |minor
> Component|c |target
> Keywords| |missed-optimization
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
>
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
--
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* [Bug c/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (9 preceding siblings ...)
2004-10-20 18:34 ` schlie at comcast dot net
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From: pinskia at gcc dot gnu dot org @ 2004-10-20 18:50 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-20 18:50 -------
>From C99
(6.5.5/3): The usual arithmetic conversions are performed on the operands.
6.3.1.8 Usual arithmetic conversions
Otherwise, the integer promotions are performed on both operands. Then the following rules are
applied to the promoted operands: If both operands have the same type, then no further conversion is
needed. Otherwise, if both operands have signed integer types or both have unsigned integer types, the
operand with the type of lesser integer conversion rank is converted to the type of the operand with
greater rank. Otherwise, if the operand that has unsigned integer type has rank greater or equal to the
rank of the type of the other operand, then the operand with signed integer type is converted to the
type of the operand with unsigned integer type. Otherwise, if the type of the operand with signed
integer type can represent all of the values of the type of the operand with unsigned integer type, then
the operand with unsigned integer type is converted to the type of the operand with signed integer
type. Otherwise, both operands are converted to the unsigned integer type corresponding to the type of
the operand with signed integer type.
This is still not wrong code as signed char signed extended to int is still the same number but this is
not a target problem but a front-end problem now.
To make sure that I read the statement correctly from the standard, it says if the types are the same
there is no need to promote the value at all.
--
What |Removed |Added
----------------------------------------------------------------------------
Severity|minor |normal
Component|target |c
Summary|not using qi version of |usual arithmetic conversion
|divmod |not applying correctly
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
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* [Bug c/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
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2004-10-20 18:50 ` [Bug c/18065] usual arithmetic conversion not applying correctly pinskia at gcc dot gnu dot org
@ 2004-10-20 19:14 ` schlie at comcast dot net
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From: schlie at comcast dot net @ 2004-10-20 19:14 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2004-10-20 19:14 -------
Subject: Re: usual arithmetic conversion not applying
correctly
Please read rule 1:
"If both operands have the same type, then no further conversion is
needed." (no promotion to int is specified or implied as being required)
Seems plain enough to me, what makes you think that:
char + char => int + int ?
short + short => int + int ?
That would imply, QI mode (and HI mode typical of shorts on 32 bit machines)
rtl instruction definitions are meaningless which isn't the case; as their
definition defines the char and short operand rtl operator -> code
transformation.
The front end has no business promoting all char and short arithmetic
operands to ints, and in fact it doesn't; so am not sure what your thinking?
-paul-
> From: pinskia at gcc dot gnu dot org <gcc-bugzilla@gcc.gnu.org>
> Reply-To: <gcc-bugzilla@gcc.gnu.org>
> Date: 20 Oct 2004 18:50:01 -0000
> To: <schlie@comcast.net>
> Subject: [Bug c/18065] usual arithmetic conversion not applying correctly
>
>
> ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-20
> 18:50 -------
> From C99
> (6.5.5/3): The usual arithmetic conversions are performed on the operands.
>
> 6.3.1.8 Usual arithmetic conversions
> Otherwise, the integer promotions are performed on both operands. Then the
> following rules are
> applied to the promoted operands: If both operands have the same type, then no
> further conversion is
> needed. Otherwise, if both operands have signed integer types or both have
> unsigned integer types, the
> operand with the type of lesser integer conversion rank is converted to the
> type of the operand with
> greater rank. Otherwise, if the operand that has unsigned integer type has
> rank greater or equal to the
> rank of the type of the other operand, then the operand with signed integer
> type is converted to the
> type of the operand with unsigned integer type. Otherwise, if the type of the
> operand with signed
> integer type can represent all of the values of the type of the operand with
> unsigned integer type, then
> the operand with unsigned integer type is converted to the type of the operand
> with signed integer
> type. Otherwise, both operands are converted to the unsigned integer type
> corresponding to the type of
> the operand with signed integer type.
>
> This is still not wrong code as signed char signed extended to int is still
> the same number but this is
> not a target problem but a front-end problem now.
>
> To make sure that I read the statement correctly from the standard, it says if
> the types are the same
> there is no need to promote the value at all.
>
> --
> What |Removed |Added
> ----------------------------------------------------------------------------
> Severity|minor |normal
> Component|target |c
> Summary|not using qi version of |usual arithmetic conversion
> |divmod |not applying correctly
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
>
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
--
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* [Bug c/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (11 preceding siblings ...)
2004-10-20 19:14 ` schlie at comcast dot net
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2004-10-20 19:25 ` pinskia at gcc dot gnu dot org
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From: pinskia at gcc dot gnu dot org @ 2004-10-20 19:18 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-20 19:18 -------
But the front-end is doing the promotions where the problem comes from, nowhere else (I am using
4.0 to verify my claim that the front-end is actually doing the promotion).
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
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* [Bug c/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
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From: pinskia at gcc dot gnu dot org @ 2004-10-20 19:25 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-20 19:25 -------
The promotion is coming from:
if (convert_p)
{
op0 = default_conversion (orig_op0);
op1 = default_conversion (orig_op1);
}
else
{
op0 = orig_op0;
op1 = orig_op1;
}
Maybe this should be changed ....
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug c/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
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From: pinskia at gcc dot gnu dot org @ 2004-10-20 19:29 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-20 19:29 -------
And the reason why we don't shoten back to signed char % signed char:
/* Although it would be tempting to shorten always here, that loses
on some targets, since the modulo instruction is undefined if the
quotient can't be represented in the computation mode. We shorten
only if unsigned or if dividing by something we know != -1. */
So maybe this is correct.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug c/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (14 preceding siblings ...)
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From: schlie at comcast dot net @ 2004-10-20 19:33 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2004-10-20 19:33 -------
Subject: Re: usual arithmetic conversion not applying
correctly
Maybe the confusion is that you're not recognizing that:
char, short, int, long, long long, are all integer types, with different
storage formats.
As opposed to enum or bit-field for example which should likely be converted
to an "integer type" with ideally the smallest and/or most efficient
representation specified for the machine, prior to an "integer" oriented
operation being performed.
???
-paul-
> From: Paul Schlie <schlie@comcast.net>
> Date: Wed, 20 Oct 2004 15:14:08 -0400
> To: <gcc-bugzilla@gcc.gnu.org>
> Subject: Re: [Bug c/18065] usual arithmetic conversion not applying correctly
>
> Please read rule 1:
>
> "If both operands have the same type, then no further conversion is
> needed." (no promotion to int is specified or implied as being required)
>
> Seems plain enough to me, what makes you think that:
>
> char + char => int + int ?
> short + short => int + int ?
>
> That would imply, QI mode (and HI mode typical of shorts on 32 bit machines)
> rtl instruction definitions are meaningless which isn't the case; as their
> definition defines the char and short operand rtl operator -> code
> transformation.
>
> The front end has no business promoting all char and short arithmetic operands
> to ints, and in fact it doesn't; so am not sure what your thinking?
>
> -paul-
>
>> From: pinskia at gcc dot gnu dot org <gcc-bugzilla@gcc.gnu.org>
>> Reply-To: <gcc-bugzilla@gcc.gnu.org>
>> Date: 20 Oct 2004 18:50:01 -0000
>> To: <schlie@comcast.net>
>> Subject: [Bug c/18065] usual arithmetic conversion not applying correctly
>>
>>
>> ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-20
>> 18:50 -------
>> From C99
>> (6.5.5/3): The usual arithmetic conversions are performed on the operands.
>>
>> 6.3.1.8 Usual arithmetic conversions
>> Otherwise, the integer promotions are performed on both operands. Then the
>> following rules are
>> applied to the promoted operands: If both operands have the same type, then
>> no
>> further conversion is
>> needed. Otherwise, if both operands have signed integer types or both have
>> unsigned integer types, the
>> operand with the type of lesser integer conversion rank is converted to the
>> type of the operand with
>> greater rank. Otherwise, if the operand that has unsigned integer type has
>> rank greater or equal to the
>> rank of the type of the other operand, then the operand with signed integer
>> type is converted to the
>> type of the operand with unsigned integer type. Otherwise, if the type of the
>> operand with signed
>> integer type can represent all of the values of the type of the operand with
>> unsigned integer type, then
>> the operand with unsigned integer type is converted to the type of the
>> operand
>> with signed integer
>> type. Otherwise, both operands are converted to the unsigned integer type
>> corresponding to the type of
>> the operand with signed integer type.
>>
>> This is still not wrong code as signed char signed extended to int is still
>> the same number but this is
>> not a target problem but a front-end problem now.
>>
>> To make sure that I read the statement correctly from the standard, it says
>> if
>> the types are the same
>> there is no need to promote the value at all.
>>
>> --
>> What |Removed |Added
>> ----------------------------------------------------------------------------
>> Severity|minor |normal
>> Component|target |c
>> Summary|not using qi version of |usual arithmetic conversion
>> |divmod |not applying correctly
>>
>>
>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
>>
>> ------- You are receiving this mail because: -------
>> You reported the bug, or are watching the reporter.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug c/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (15 preceding siblings ...)
2004-10-20 19:33 ` schlie at comcast dot net
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2004-10-20 21:19 ` schlie at comcast dot net
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From: pinskia at gcc dot gnu dot org @ 2004-10-20 19:54 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-20 19:54 -------
When I am talking about promoting means that we add casts. aka sc%sc gets changed to (signed char)
(((int)sc)%((int)sc)).
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug c/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (16 preceding siblings ...)
2004-10-20 19:54 ` pinskia at gcc dot gnu dot org
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From: schlie at comcast dot net @ 2004-10-20 21:19 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2004-10-20 21:19 -------
Subject: Re: usual arithmetic conversion not applying
correctly
Andrew,
Yes, and with respect to / and % operations:
- the modulo/reminder result can always be represented in the same type
and size as its divisor/modulus operand, regardless of the dividend's
type and size.
- the quotient result can always be represented in the same type and size
as it's dividend, if it's divisor/modulus operand is unsigned, otherwise
ideally to be promoted to it's next larger signed type to preserve
accuracy if useful, but typically irrelevant, as operator result
precision is in most practical circumstances determined by the precision
of the result's need, therefore in typical cases like int = int / int
no value is derived from pretending to preserve idealized accuracy,
therefore CPU's typically implement instructions to yield the equivalent
results that would have been attained if the precision were maintained,
and then simply truncated when assigned to it's destination type for
typical integer operations but mark an under or overflow flag, just as
int = int + int; would overflow; therefore for all practical purposes,
integer operands should never be promoted beyond their need, nor should
operation precision be required beyond it's result's need.
(and just to double check, this needs to get fixed on 3.4.3 too, which
I honestly suspect is related to the rtl interpretation, as other QI
mode instruction specifications are properly matched as expected.)
(also it's likely that these type of problems predominantly express
themselves on small target machines, as on larger 32/64 bit machines,
operations physically occur on correspondingly wide cpu's, therefore
don't enable inappropriate operand promotion errors to be easily
observable.)
-paul-
> From: pinskia at gcc dot gnu dot org <gcc-bugzilla@gcc.gnu.org>
> Reply-To: <gcc-bugzilla@gcc.gnu.org>
> Date: 20 Oct 2004 19:29:13 -0000
> To: <schlie@comcast.net>
> Subject: [Bug c/18065] usual arithmetic conversion not applying correctly
>
>
> ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-20
> 19:29 -------
> And the reason why we don't shoten back to signed char % signed char:
>
> /* Although it would be tempting to shorten always here, that loses
> on some targets, since the modulo instruction is undefined if the
> quotient can't be represented in the computation mode. We shorten
> only if unsigned or if dividing by something we know != -1. */
>
> So maybe this is correct.
>
> --
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
>
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
--
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* [Bug c/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
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2004-10-20 21:19 ` schlie at comcast dot net
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2004-10-20 21:31 ` jsm at polyomino dot org dot uk
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From: pinskia at gcc dot gnu dot org @ 2004-10-20 21:25 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-20 21:25 -------
As I have said before, this has nothing to RTL, only the front-end. Read the code which I copied from
the GCC, this is in the front-end.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug c/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
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2004-10-20 21:25 ` pinskia at gcc dot gnu dot org
@ 2004-10-20 21:31 ` jsm at polyomino dot org dot uk
2004-10-20 21:46 ` schlie at comcast dot net
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From: jsm at polyomino dot org dot uk @ 2004-10-20 21:31 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From jsm at polyomino dot org dot uk 2004-10-20 21:31 -------
Subject: Re: usual arithmetic conversion not applying correctly
On Wed, 20 Oct 2004, pinskia at gcc dot gnu dot org wrote:
> Otherwise, the integer promotions are performed on both operands. Then
> the following rules are applied to the promoted operands: If both
> operands have the same type, then no further conversion is needed.
The integer promotions are where signed char is promoted to int. Only
after then are types compared.
It is not the job of the front end to optimise code. The front end should
generate datastructures corresponding exactly to the specified semantics
of the language, including the promotions in this case. Subsequent
passes, preferably on GIMPLE but maybe including fold at present, can deal
with eliminating conversions not needed for code generation.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug c/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
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@ 2004-10-20 21:46 ` schlie at comcast dot net
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From: schlie at comcast dot net @ 2004-10-20 21:46 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2004-10-20 21:46 -------
Subject: Re: usual arithmetic conversion not applying
correctly
Andrew,
And if it's already declared as, or cast to signed char's in the code?
unsigned char x, y ;
(signed char)x = (signed char)x / (signed char)y ;
-or- (should yield identical code, and require no promotions or conversions)
signed char x, y ;
x = x / y ; the only arguable possible type conversion that may be required
; would be to convert the result of (x / y) which may have been
; implemented by the target machine as having a wider result, but
; not required if it's destination storage does not require it.
(there's no reason to ever muck with specified object types unless it's
value needs to converted as required for assignment, or the specified
semantics of an operation; but even then, the type of the object doesn't
change, although the its value's representation may if required.)
-paul-
> From: pinskia at gcc dot gnu dot org <gcc-bugzilla@gcc.gnu.org>
> Reply-To: <gcc-bugzilla@gcc.gnu.org>
> Date: 20 Oct 2004 19:54:55 -0000
> To: <schlie@comcast.net>
> Subject: [Bug c/18065] usual arithmetic conversion not applying correctly
>
>
> ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-20
> 19:54 -------
> When I am talking about promoting means that we add casts. aka sc%sc gets
> changed to (signed char)
> (((int)sc)%((int)sc)).
>
> --
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
>
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug c/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (20 preceding siblings ...)
2004-10-20 21:46 ` schlie at comcast dot net
@ 2004-10-20 22:27 ` schlie at comcast dot net
2004-10-20 22:31 ` [Bug tree-optimization/18065] " pinskia at gcc dot gnu dot org
` (10 subsequent siblings)
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From: schlie at comcast dot net @ 2004-10-20 22:27 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2004-10-20 22:27 -------
Subject: Re: usual arithmetic conversion not applying
correctly
Andrew,
It has nothing to do with "optimizing code", if the 3.X and 4.X front-ends
are promoting the size of anything other than bool, enum, or bit-field
operand values without explicit need, they're doing so in error, and in
contradiction to the standard's semantics.
(could you please check on this, as it should be clear that it's wrong,
although may have gone unnoticed as most of GCC's targets are 32+ bit
machines, and would have escaped detection, as on most larger machines
most operations are converted by default to int as that's all they
know about, it's only when the result is stored, does the operations
required size express itself. It's a pretty major screw-up to presume
all target machines are large, and then to encode that presumption into
C's front end; not to mention it seems pretty stupid to do, and then
worry about trying to optimize operand values into smaller sizes when
subsequently realizing that their size promotion was not required, and
calling it an optimization; the whole mess is more accurately a
de-optimization, and perversion of C's semantics.)
Thanks, -paul-
> From: jsm at polyomino dot org dot uk <gcc-bugzilla@gcc.gnu.org>
> Reply-To: <gcc-bugzilla@gcc.gnu.org>
> Date: 20 Oct 2004 21:31:15 -0000
> To: <schlie@comcast.net>
> Subject: [Bug c/18065] usual arithmetic conversion not applying correctly
>
>
> ------- Additional Comments From jsm at polyomino dot org dot uk 2004-10-20
> 21:31 -------
> Subject: Re: usual arithmetic conversion not applying correctly
>
> On Wed, 20 Oct 2004, pinskia at gcc dot gnu dot org wrote:
>
>> Otherwise, the integer promotions are performed on both operands. Then
>> the following rules are applied to the promoted operands: If both
>> operands have the same type, then no further conversion is needed.
>
> The integer promotions are where signed char is promoted to int. Only
> after then are types compared.
>
> It is not the job of the front end to optimise code. The front end should
> generate datastructures corresponding exactly to the specified semantics
> of the language, including the promotions in this case. Subsequent
> passes, preferably on GIMPLE but maybe including fold at present, can deal
> with eliminating conversions not needed for code generation.
>
> --
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
>
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug tree-optimization/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
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@ 2004-10-20 22:31 ` pinskia at gcc dot gnu dot org
2004-10-20 22:42 ` jsm at polyomino dot org dot uk
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From: pinskia at gcc dot gnu dot org @ 2004-10-20 22:31 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-20 22:31 -------
That was not me writting that but a C front-end person so why did you write Andrew?
--
What |Removed |Added
----------------------------------------------------------------------------
Component|c |tree-optimization
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug tree-optimization/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (22 preceding siblings ...)
2004-10-20 22:31 ` [Bug tree-optimization/18065] " pinskia at gcc dot gnu dot org
@ 2004-10-20 22:42 ` jsm at polyomino dot org dot uk
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From: jsm at polyomino dot org dot uk @ 2004-10-20 22:42 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From jsm at polyomino dot org dot uk 2004-10-20 22:41 -------
Subject: Re: usual arithmetic conversion not applying correctly
On Wed, 20 Oct 2004, schlie at comcast dot net wrote:
> It's a pretty major screw-up to presume
> all target machines are large, and then to encode that presumption into
> C's front end; not to mention it seems pretty stupid to do, and then
This is not a GCC presumption, it is a property of the C language that
there are certain promotions that may not be optimally efficient for 8-bit
targets. If there is a "major screw-up", it is either in the choice to
use a language designed for systems that are at least 16-bit on an 8-bit
target, or in the language design if you think 8-bit targets should have
been given greater importance when the language was being standardised in
the 1980s; it is nothing to do with the front end. The AVR target has a
-mint8 option which puts the compiler in a nonconforming mode with 8-bit
int, which might however give you better code than you can get with
standard C on an 8-bit target.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug tree-optimization/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (23 preceding siblings ...)
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@ 2004-10-20 23:03 ` jsm at polyomino dot org dot uk
2004-10-20 23:28 ` schlie at comcast dot net
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From: jsm at polyomino dot org dot uk @ 2004-10-20 23:03 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From jsm at polyomino dot org dot uk 2004-10-20 23:03 -------
Subject: Re: C integer promotion semantics /
front end problems.
I presume you sent your message directly to me by mistake, so am sending
the reply back to the bug database so it can benefit more than one person.
Technical messages about public GCC versions should, absent any more
specific support arrangements in a particular case, go to the mailing
lists, not individuals; questions are answered in public GCC development
for the benefit of the public.
On Wed, 20 Oct 2004, Paul Schlie wrote:
> Sorry to do this to you again, but where do you see in the standard the
> requirement to promote, or license to needlessly promote all operands
> to int?
C99 subclause 6.3.1.1 paragraph 2. signed char has rank less than that of
int, so it *must* be promoted to int. What happens afterwards is nothing
to do with the front end. The front end does *too many* optimisations; it
should purely generate GIMPLE representing the standard meaning of the
code and leave it to the later stages to tell that such conversions - or
indeed conversions between int and long where they are the same size - can
be optimised away in some cases.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug tree-optimization/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (24 preceding siblings ...)
2004-10-20 23:03 ` jsm at polyomino dot org dot uk
@ 2004-10-20 23:28 ` schlie at comcast dot net
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From: schlie at comcast dot net @ 2004-10-20 23:28 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2004-10-20 23:28 -------
Subject: Re: usual arithmetic conversion not
applying correctly
What size promotion is required for char sized integer operations?
I see none?
What size promotion is required for short sized integer operations?
I see none?
The standard's refers to (as below earlier already referenced by Andrew):
- "integer" promotion is performed on both operands, and then further size
and/or sign-type converted as required if the operands aren't already of the
same "integer" type.
"integer type" not "int"; char, short, int, long are "integer types" of
different rank, yes?
The only primitive storage classes in C which aren't intrinsically an
"integer type" are: bool, enum, and bit-fields to my knowledge, which
require implicit promotion to an "integer type" to be operated on.
Even if you said that char's aren't "integer types" it's easy enough to
define short as having the same size as char, thereby promote char->short
which is surely an "integer type", although char's already are.
Where am I missing it?
>From C99
(6.5.5/3): The usual arithmetic conversions are performed on the operands.
6.3.1.8 Usual arithmetic conversions
Otherwise, the integer promotions are performed on both operands. Then the
following rules are
applied to the promoted operands: If both operands have the same type, then
no further conversion is
needed. Otherwise, if both operands have signed integer types or both have
unsigned integer types, the
operand with the type of lesser integer conversion rank is converted to the
type of the operand with
greater rank. Otherwise, if the operand that has unsigned integer type has
rank greater or equal to the
rank of the type of the other operand, then the operand with signed integer
type is converted to the
type of the operand with unsigned integer type. Otherwise, if the type of
the operand with signed
integer type can represent all of the values of the type of the operand with
unsigned integer type, then
the operand with unsigned integer type is converted to the type of the
operand with signed integer
type. Otherwise, both operands are converted to the unsigned integer type
corresponding to the type of
the operand with signed integer type.
> From: jsm at polyomino dot org dot uk <gcc-bugzilla@gcc.gnu.org>
> Reply-To: <gcc-bugzilla@gcc.gnu.org>
> Date: 20 Oct 2004 22:41:59 -0000
> To: <schlie@comcast.net>
> Subject: [Bug tree-optimization/18065] usual arithmetic conversion not
> applying correctly
>
>
> ------- Additional Comments From jsm at polyomino dot org dot uk 2004-10-20
> 22:41 -------
> Subject: Re: usual arithmetic conversion not applying correctly
>
> On Wed, 20 Oct 2004, schlie at comcast dot net wrote:
>
>> It's a pretty major screw-up to presume
>> all target machines are large, and then to encode that presumption into
>> C's front end; not to mention it seems pretty stupid to do, and then
>
> This is not a GCC presumption, it is a property of the C language that
> there are certain promotions that may not be optimally efficient for 8-bit
> targets. If there is a "major screw-up", it is either in the choice to
> use a language designed for systems that are at least 16-bit on an 8-bit
> target, or in the language design if you think 8-bit targets should have
> been given greater importance when the language was being standardised in
> the 1980s; it is nothing to do with the front end. The AVR target has a
> -mint8 option which puts the compiler in a nonconforming mode with 8-bit
> int, which might however give you better code than you can get with
> standard C on an 8-bit target.
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
>
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug tree-optimization/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (25 preceding siblings ...)
2004-10-20 23:28 ` schlie at comcast dot net
@ 2004-10-21 1:04 ` schlie at comcast dot net
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From: schlie at comcast dot net @ 2004-10-21 1:04 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2004-10-21 01:04 -------
Subject: Re: usual arithmetic conversion not
applying correctly
Ok, a more basic observation/recommendation: the front end should not be
masking true operand types by promoting them prematurely, as it generates
very little value, while needlessly complicating the back-end's ability to
easily generate optimal code for non-integer width machines; as with
efficient access to the true source operand precision, and true operation
result precision requirements, the back end can then easily and directly
leverage the target's rtl machine description to generate fully conforming
precision code, with out the burden of having to back-out prematurely
applied type conversions (which seem wholly counterproductive).
(which of course is the point of being able to specify optimal QI, and in
many cases HI mode rtl instruction mappings, which have been made much less
efficient by the front-end's choice to needlessly prematurely type promote
operands prior to the literal requirement to do so.)
Thanks for hearing me out, and by the way this whole discussion began by
observing that GCC was not utilizing efficient rtl QI mode instruction
descriptions, resulting in the classification of the bug as a "missed
optimization" bug, as opposed to an "incorrect code" bug, with the
explanation that although the source and destination operands specified
in C could be implemented as specified in the rtl instruction mapping
specification and be fully conforming, it wasn't recognized because the
back-end didn't find the "optimization" because the front-end needlessly
prematurely type converted all operands passed to the back-end.
And for what little it may be worth, for good or bad, the factual reality
is that there are 100's of times more small processors programmed and
deployed in products than there are 32+ bit processors, therefore it would
be nice if GCC didn't needless restrict itself to being most optimally
applicable to larger machines at the expense of smaller machines (as there
far more commercial 8 and 16 bit processors available from companies
interested in support than their are 32-64 bit processor companies, and
likely to remain that way, so it's not likely good business to bite the
hand that may feed you).
-paul-
> From: jsm at polyomino dot org dot uk <gcc-bugzilla@gcc.gnu.org>
> Reply-To: <gcc-bugzilla@gcc.gnu.org>
> Date: 20 Oct 2004 23:03:15 -0000
> To: <schlie@comcast.net>
> Subject: [Bug tree-optimization/18065] usual arithmetic conversion not
> applying correctly
>
>
> ------- Additional Comments From jsm at polyomino dot org dot uk 2004-10-20
> 23:03 -------
> Subject: Re: C integer promotion semantics /
> front end problems.
>
> I presume you sent your message directly to me by mistake, so am sending
> the reply back to the bug database so it can benefit more than one person.
> Technical messages about public GCC versions should, absent any more
> specific support arrangements in a particular case, go to the mailing
> lists, not individuals; questions are answered in public GCC development
> for the benefit of the public.
>
> On Wed, 20 Oct 2004, Paul Schlie wrote:
>
>> Sorry to do this to you again, but where do you see in the standard the
>> requirement to promote, or license to needlessly promote all operands
>> to int?
>
> C99 subclause 6.3.1.1 paragraph 2. signed char has rank less than that of
> int, so it *must* be promoted to int. What happens afterwards is nothing
> to do with the front end. The front end does *too many* optimisations; it
> should purely generate GIMPLE representing the standard meaning of the
> code and leave it to the later stages to tell that such conversions - or
> indeed conversions between int and long where they are the same size - can
> be optimised away in some cases.
>
> --
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
>
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug tree-optimization/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (26 preceding siblings ...)
2004-10-21 1:04 ` schlie at comcast dot net
@ 2004-10-21 1:28 ` schlie at comcast dot net
2004-10-21 12:47 ` bangerth at dealii dot org
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From: schlie at comcast dot net @ 2004-10-21 1:28 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2004-10-21 01:28 -------
Subject: Re: usual arithmetic conversion not applying
correctly
Andrew,
So regardless of the all other things, it seems minimally clear that
the promotion code as it stands now should allow the required result type
to be shortened to the size and type of the modulus operand for modulus
operations; and to the size and type of the dividend operand if the divisor
is unsigned, and the required result precision promoted to the next larger
signed type otherwise (although not strictly required if the true
destination's precision requirement is less). Which should address the short
term problem associated with type promotion being done by the front end.
-paul-
> From: Paul Schlie <schlie@comcast.net>
> Date: Wed, 20 Oct 2004 17:19:24 -0400
> To: <gcc-bugzilla@gcc.gnu.org>
> Subject: Re: [Bug c/18065] usual arithmetic conversion not applying correctly
>
> Andrew,
>
> Yes, and with respect to / and % operations:
>
> - the modulo/reminder result can always be represented in the same type
> and size as its divisor/modulus operand, regardless of the dividend's
> type and size.
>
> - the quotient result can always be represented in the same type and size
> as it's dividend, if it's divisor/modulus operand is unsigned, otherwise
> ideally to be promoted to it's next larger signed type to preserve
> accuracy if useful, but typically irrelevant, as operator result
> precision is in most practical circumstances determined by the precision
> of the result's need, therefore in typical cases like int = int / int
> no value is derived from pretending to preserve idealized accuracy,
> therefore CPU's typically implement instructions to yield the equivalent
> results that would have been attained if the precision were maintained,
> and then simply truncated when assigned to it's destination type for
> typical integer operations but mark an under or overflow flag, just as
> int = int + int; would overflow; therefore for all practical purposes,
> integer operands should never be promoted beyond their need, nor should
> operation precision be required beyond it's result's need.
>
> (and just to double check, this needs to get fixed on 3.4.3 too, which
> I honestly suspect is related to the rtl interpretation, as other QI
> mode instruction specifications are properly matched as expected.)
>
> (also it's likely that these type of problems predominantly express
> themselves on small target machines, as on larger 32/64 bit machines,
> operations physically occur on correspondingly wide cpu's, therefore
> don't enable inappropriate operand promotion errors to be easily
> observable.)
>
> -paul-
>
>> From: pinskia at gcc dot gnu dot org <gcc-bugzilla@gcc.gnu.org>
>> Reply-To: <gcc-bugzilla@gcc.gnu.org>
>> Date: 20 Oct 2004 19:29:13 -0000
>> To: <schlie@comcast.net>
>> Subject: [Bug c/18065] usual arithmetic conversion not applying correctly
>>
>>
>> ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-20
>> 19:29 -------
>> And the reason why we don't shoten back to signed char % signed char:
>>
>> /* Although it would be tempting to shorten always here, that loses
>> on some targets, since the modulo instruction is undefined if the
>> quotient can't be represented in the computation mode. We shorten
>> only if unsigned or if dividing by something we know != -1. */
>>
>> So maybe this is correct.
>>
>> --
>>
>>
>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
>>
>> ------- You are receiving this mail because: -------
>> You reported the bug, or are watching the reporter.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug tree-optimization/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (27 preceding siblings ...)
2004-10-21 1:28 ` schlie at comcast dot net
@ 2004-10-21 12:47 ` bangerth at dealii dot org
2004-12-21 20:50 ` schlie at comcast dot net
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From: bangerth at dealii dot org @ 2004-10-21 12:47 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From bangerth at dealii dot org 2004-10-21 12:47 -------
> And for what little it may be worth, for good or bad, the factual reality
> is that there are 100's of times more small processors programmed and
> deployed in products than there are 32+ bit processors, therefore it would
> be nice if GCC didn't needless restrict itself to being most optimally
> applicable to larger machines at the expense of smaller machines (as there
> far more commercial 8 and 16 bit processors available from companies
> interested in support than their are 32-64 bit processor companies, and
> likely to remain that way, so it's not likely good business to bite the
> hand that may feed you).
Just to have this (obvious) fact mentioned in this thread also: as a
developer starved project, we are always grateful for patches people may
send that improve the behavior of gcc. Your company may also be interested
in hiring gcc developers to implement features you need.
W.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug tree-optimization/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (28 preceding siblings ...)
2004-10-21 12:47 ` bangerth at dealii dot org
@ 2004-12-21 20:50 ` schlie at comcast dot net
2005-01-16 1:39 ` pinskia at gcc dot gnu dot org
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From: schlie at comcast dot net @ 2004-12-21 20:50 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2004-12-21 20:50 -------
(although not the most elegant fix)
This fixes the rest of the problem, as there's no reaon to default promote smaller than int sized
integers to int, they will end up being promoted if required by the back-end if the target requires
them to be (also should not need to litterally promote enum's and bool beyond the smallest int
type with suffecient to represent it's value range):
(called via default_conversion() to determine if an expression should be converted by default to int)
*** In File: c-common.c ***
bool
c_promoting_integer_type_p (tree t)
{
switch (TREE_CODE (t))
{
- case INTEGER_TYPE:
- return (TYPE_MAIN_VARIANT (t) == char_type_node
- || TYPE_MAIN_VARIANT (t) == signed_char_type_node
- || TYPE_MAIN_VARIANT (t) == unsigned_char_type_node
- || TYPE_MAIN_VARIANT (t) == short_integer_type_node
- || TYPE_MAIN_VARIANT (t) == short_unsigned_type_node
- || TYPE_PRECISION (t) < TYPE_PRECISION (integer_type_node)); pws--*/
-
case ENUMERAL_TYPE:
/* ??? Technically all enumerations not larger than an int
promote to an int. But this is used along code paths
that only want to notice a size change. */
return TYPE_PRECISION (t) < TYPE_PRECISION (integer_type_node);
case BOOLEAN_TYPE:
return 1;
default:
return 0;
}
}
*** end ***
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug tree-optimization/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (29 preceding siblings ...)
2004-12-21 20:50 ` schlie at comcast dot net
@ 2005-01-16 1:39 ` pinskia at gcc dot gnu dot org
2005-01-16 7:17 ` schlie at comcast dot net
2005-01-16 17:39 ` schlie at comcast dot net
32 siblings, 0 replies; 40+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-01-16 1:39 UTC (permalink / raw)
To: gcc-bugs
--
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |enhancement
Priority|P1 |P3
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug tree-optimization/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (30 preceding siblings ...)
2005-01-16 1:39 ` pinskia at gcc dot gnu dot org
@ 2005-01-16 7:17 ` schlie at comcast dot net
2005-01-16 17:39 ` schlie at comcast dot net
32 siblings, 0 replies; 40+ messages in thread
From: schlie at comcast dot net @ 2005-01-16 7:17 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2005-01-16 07:16 -------
Subject: Re: usual arithmetic conversion not
applying correctly
Wonder if this PR could still be considered a missed optimization, as the
present logic which determines if an / or % expression's operands may be
shortened, misses the case where if the lhs operand is a constant, it may
be verified as not being INT_MIN; as if it's not, then it's impossible for
the operation to overflow, i.e. INT_MIN / -1 => INT_MAX+1, therefore
may be shortened. As noted as being absent in it's comment on shortening:
/* Although it would be tempting to shorten always here, that loses
on some targets, since the modulo instruction is undefined if the
quotient can't be represented in the computation mode. We shorten
only if unsigned or if dividing by something we know != -1. */
> From: pinskia at gcc dot gnu dot org <gcc-bugzilla@gcc.gnu.org>
> Subject: [Bug tree-optimization/18065] usual arithmetic conversion not
> applying correctly
>
> --
> What |Removed |Added
> ----------------------------------------------------------------------------
> Severity|normal |enhancement
> Priority|P1 |P3
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug tree-optimization/18065] usual arithmetic conversion not applying correctly
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
` (31 preceding siblings ...)
2005-01-16 7:17 ` schlie at comcast dot net
@ 2005-01-16 17:39 ` schlie at comcast dot net
32 siblings, 0 replies; 40+ messages in thread
From: schlie at comcast dot net @ 2005-01-16 17:39 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2005-01-16 17:39 -------
Subject: Re: usual arithmetic conversion not
applying correctly
> From: schlie at comcast dot net <gcc-bugzilla@gcc.gnu.org>
> ------- Additional Comments From schlie at comcast dot net 2005-01-16 07:16
> Subject: Re: usual arithmetic conversion not applying correctly
>
> Wonder if this PR could still be considered a missed optimization, as the
> present logic which determines if an / or % expression's operands may be
> shortened, misses the case where if the lhs operand is a constant, it may
> be verified as not being INT_MIN; as if it's not, then it's impossible for
> the operation to overflow, i.e. INT_MIN / -1 => INT_MAX+1, therefore
> may be shortened. As noted as being absent in it's comment on shortening:
>
> /* Although it would be tempting to shorten always here, that loses
> on some targets, since the modulo instruction is undefined if the
> quotient can't be represented in the computation mode. We shorten
> only if unsigned or if dividing by something we know != -1. */
- It would be unfortunate if / and % couldn't be somewhat further optimized
prior to 4.0 when their lhs operands are known not to be INT_MIN, as they
tend to be typically relatively expensive operations, likely benefiting
from shortening more than most.
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
>
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
[parent not found: <bug-18065-9497@http.gcc.gnu.org/bugzilla/>]
* [Bug tree-optimization/18065] usual arithmetic conversion not applying correctly
[not found] <bug-18065-9497@http.gcc.gnu.org/bugzilla/>
@ 2010-09-14 7:06 ` abnikant dot singh at atmel dot com
2010-09-14 7:13 ` abnikant dot singh at atmel dot com
1 sibling, 0 replies; 40+ messages in thread
From: abnikant dot singh at atmel dot com @ 2010-09-14 7:06 UTC (permalink / raw)
To: gcc-bugs
------- Comment #34 from abnikant dot singh at atmel dot com 2010-09-14 07:06 -------
Yeah, this is happening because of the type promotion in gcc/c-common.c in the
function c_promoting_integer_type_p. See this:
/* Nonzero if the type T promotes to int. This is (nearly) the
integral promotions defined in ISO C99 6.3.1.1/2. */
bool
c_promoting_integer_type_p (const_tree t)
{
switch (TREE_CODE (t))
{
case INTEGER_TYPE:
return (TYPE_MAIN_VARIANT (t) == char_type_node
|| TYPE_MAIN_VARIANT (t) == signed_char_type_node
|| TYPE_MAIN_VARIANT (t) == unsigned_char_type_node
|| TYPE_MAIN_VARIANT (t) == short_integer_type_node
|| TYPE_MAIN_VARIANT (t) == short_unsigned_type_node
|| TYPE_PRECISION (t) < TYPE_PRECISION (integer_type_node));
case ENUMERAL_TYPE:
/* ??? Technically all enumerations not larger than an int
promote to an int. But this is used along code paths
that only want to notice a size change. */
return TYPE_PRECISION (t) < TYPE_PRECISION (integer_type_node);
case BOOLEAN_TYPE:
return 1;
default:
return 0;
}
}
So by commenting the case INTEGER_TYPE, we will get the call to _divmodqi4, but
I don't think this is the right thing to do.
--
abnikant dot singh at atmel dot com changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |abnikant dot singh at atmel
| |dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
* [Bug tree-optimization/18065] usual arithmetic conversion not applying correctly
[not found] <bug-18065-9497@http.gcc.gnu.org/bugzilla/>
2010-09-14 7:06 ` abnikant dot singh at atmel dot com
@ 2010-09-14 7:13 ` abnikant dot singh at atmel dot com
1 sibling, 0 replies; 40+ messages in thread
From: abnikant dot singh at atmel dot com @ 2010-09-14 7:13 UTC (permalink / raw)
To: gcc-bugs
------- Comment #35 from abnikant dot singh at atmel dot com 2010-09-14 07:13 -------
In the head c-common.c is placed in gcc/c-family/c-common.c
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18065
^ permalink raw reply [flat|nested] 40+ messages in thread
[parent not found: <bug-18065-4@http.gcc.gnu.org/bugzilla/>]
end of thread, other threads:[~2012-05-24 14:05 UTC | newest]
Thread overview: 40+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2004-10-19 20:22 [Bug c/18065] New: wrong built-in functions selected schlie at comcast dot net
2004-10-19 20:27 ` [Bug c/18065] " schlie at comcast dot net
2004-10-19 20:39 ` [Bug target/18065] " pinskia at gcc dot gnu dot org
2004-10-19 21:18 ` schlie at comcast dot net
2004-10-19 21:31 ` schlie at comcast dot net
2004-10-19 21:39 ` [Bug target/18065] not using qi version of divmod pinskia at gcc dot gnu dot org
2004-10-19 21:53 ` schlie at comcast dot net
2004-10-19 22:08 ` ericw at evcohs dot com
2004-10-19 22:31 ` schlie at comcast dot net
2004-10-19 23:13 ` ericw at evcohs dot com
2004-10-20 18:34 ` schlie at comcast dot net
2004-10-20 18:50 ` [Bug c/18065] usual arithmetic conversion not applying correctly pinskia at gcc dot gnu dot org
2004-10-20 19:14 ` schlie at comcast dot net
2004-10-20 19:18 ` pinskia at gcc dot gnu dot org
2004-10-20 19:25 ` pinskia at gcc dot gnu dot org
2004-10-20 19:29 ` pinskia at gcc dot gnu dot org
2004-10-20 19:33 ` schlie at comcast dot net
2004-10-20 19:54 ` pinskia at gcc dot gnu dot org
2004-10-20 21:19 ` schlie at comcast dot net
2004-10-20 21:25 ` pinskia at gcc dot gnu dot org
2004-10-20 21:31 ` jsm at polyomino dot org dot uk
2004-10-20 21:46 ` schlie at comcast dot net
2004-10-20 22:27 ` schlie at comcast dot net
2004-10-20 22:31 ` [Bug tree-optimization/18065] " pinskia at gcc dot gnu dot org
2004-10-20 22:42 ` jsm at polyomino dot org dot uk
2004-10-20 23:03 ` jsm at polyomino dot org dot uk
2004-10-20 23:28 ` schlie at comcast dot net
2004-10-21 1:04 ` schlie at comcast dot net
2004-10-21 1:28 ` schlie at comcast dot net
2004-10-21 12:47 ` bangerth at dealii dot org
2004-12-21 20:50 ` schlie at comcast dot net
2005-01-16 1:39 ` pinskia at gcc dot gnu dot org
2005-01-16 7:17 ` schlie at comcast dot net
2005-01-16 17:39 ` schlie at comcast dot net
[not found] <bug-18065-9497@http.gcc.gnu.org/bugzilla/>
2010-09-14 7:06 ` abnikant dot singh at atmel dot com
2010-09-14 7:13 ` abnikant dot singh at atmel dot com
[not found] <bug-18065-4@http.gcc.gnu.org/bugzilla/>
2012-05-24 14:03 ` peter777778 at hotmail dot co.uk
2012-05-24 14:04 ` peter777778 at hotmail dot co.uk
2012-05-24 14:05 ` peter777778 at hotmail dot co.uk
2012-05-24 14:23 ` peter777778 at hotmail dot co.uk
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