[Bug c/19154] New: miss-optimization of (x & pow2C) avr conditionals returning bool equivalent values

[Bug c/19154] New: miss-optimization of (x & pow2C) avr conditionals returning bool equivalent values

[schlie at comcast dot net]

/* miss-optimization of (x & pow2C) conditionals returning bool equivalent values.

   Conditional expressions returning/assigning bool equivalent values tend to
   produce less efficient generic code than those returning arbitrary values;
   GCC 3.3.3 produces the more effecient form of the results consistently. */

int main (void){

volatile char c;
volatile int i;
volatile long l;


/* char tests */

c = (c & (1 << 3)); // ok: ((char)c & C).


c = (c & (1 << 3)) ? 3 : 5; // ok: if((char)c & C) -> avr's bit-test&skip.

c = (c & (1 << 3)) ? 1 : 0; // poor: if((char)c & C) -> if(((int)c >> C') & 1), w/unnessisary (int)c 
promotion.


if (c & (1 << 3)) // ok: if((char)c & C) -> avr's bit-test&skip.
     c = 3;
else c = 5;

if (c & (1 << 3)) // ok: if((char)c & C) -> avr's bit-test&skip.
     c = 1;
else c = 0;


/* int tests */

i = i & (1 << 11); // ok: ((int)i & C)


i = (i & (1 << 11)) ? 3 : 5; // ok: if((int)i & C) -> avr's bit-test&skip.

i = (i & (1 << 11)) ? 1 : 0; // poor: if((int)i & C) -> if(((int)i >> C') & 1).


if (i & (1 << 11)) // ok: if((int)i & C) -> avr's bit-test&skip.
     i = 3;
else i = 5;
  
if (i & (1 << 11)) // poor: if((int)i & C) -> avr's bit-test&skip, but w/ineffecient return value.
     i = 1;
else i = 0;



/* long tests */

l = (l & ((long)1 << 27)); // ok: ((long)l & C)


l = (l & ((long)1 << 27)) ? 3 : 5; // ok: if((long)l & C) -> avr's bit-test&skip.

l = (l & ((long)1 << 27)) ? 1 : 0; // poor: if((long)l & C) -> if(((long)l >> C') & 1).


if (l & ((long)1 << 27)) // ok: if((long)l & C) -> avr's bit-test&skip.
     l = 3;
else l = 5;

if (l & ((long)1 << 27)) // poor: if((long)l & C) -> avr's bit-test&skip, but w/ineffecient return value.
     l = 1;
else l = 0;


return 0;

}

Produces:

int main (void){
  c6:	c8 ef       	ldi	r28, 0xF8	; 248
  c8:	d0 e1       	ldi	r29, 0x10	; 16
  ca:	de bf       	out	0x3e, r29	; 62
  cc:	cd bf       	out	0x3d, r28	; 61

volatile char c;
volatile int i;
volatile long l;


/* char tests */

c = (c & (1 << 3)); // ok: ((char)c & C).
  ce:	89 81       	ldd	r24, Y+1	; 0x01
  d0:	88 70       	andi	r24, 0x08	; 8
  d2:	89 83       	std	Y+1, r24	; 0x01


c = (c & (1 << 3)) ? 3 : 5; // ok: if((char)c & C) -> avr's bit-test&skip.
  d4:	89 81       	ldd	r24, Y+1	; 0x01
  d6:	83 ff       	sbrs	r24, 3
  d8:	02 c0       	rjmp	.+4      	; 0xde <main+0x18>
  da:	83 e0       	ldi	r24, 0x03	; 3
  dc:	01 c0       	rjmp	.+2      	; 0xe0 <main+0x1a>
  de:	85 e0       	ldi	r24, 0x05	; 5
  e0:	89 83       	std	Y+1, r24	; 0x01

c = (c & (1 << 3)) ? 1 : 0; // poor: if((char)c & C) -> if(((int)c >> C') & 1), w/unnessisary (int)c 
promotion.
  e2:	89 81       	ldd	r24, Y+1	; 0x01
  e4:	99 27       	eor	r25, r25
  e6:	43 e0       	ldi	r20, 0x03	; 3
  e8:	96 95       	lsr	r25
  ea:	87 95       	ror	r24
  ec:	4a 95       	dec	r20
  ee:	e1 f7       	brne	.-8      	; 0xe8 <main+0x22>
  f0:	81 70       	andi	r24, 0x01	; 1
  f2:	89 83       	std	Y+1, r24	; 0x01


if (c & (1 << 3)) // ok: if((char)c & C) -> avr's bit-test&skip.
  f4:	89 81       	ldd	r24, Y+1	; 0x01
  f6:	83 ff       	sbrs	r24, 3
  f8:	02 c0       	rjmp	.+4      	; 0xfe <main+0x38>
     c = 3;
  fa:	83 e0       	ldi	r24, 0x03	; 3
  fc:	01 c0       	rjmp	.+2      	; 0x100 <main+0x3a>
else c = 5;
  fe:	85 e0       	ldi	r24, 0x05	; 5
 100:	89 83       	std	Y+1, r24	; 0x01

if (c & (1 << 3)) // ok: if((char)c & C) -> avr's bit-test&skip.
 102:	89 81       	ldd	r24, Y+1	; 0x01
 104:	83 ff       	sbrs	r24, 3
 106:	03 c0       	rjmp	.+6      	; 0x10e <main+0x48>
     c = 1;
 108:	81 e0       	ldi	r24, 0x01	; 1
 10a:	89 83       	std	Y+1, r24	; 0x01
 10c:	01 c0       	rjmp	.+2      	; 0x110 <main+0x4a>
else c = 0;
 10e:	19 82       	std	Y+1, r1	; 0x01


/* int tests */

i = i & (1 << 11); // ok: ((int)i & C)
 110:	8a 81       	ldd	r24, Y+2	; 0x02
 112:	9b 81       	ldd	r25, Y+3	; 0x03
 114:	80 70       	andi	r24, 0x00	; 0
 116:	98 70       	andi	r25, 0x08	; 8
 118:	8a 83       	std	Y+2, r24	; 0x02
 11a:	9b 83       	std	Y+3, r25	; 0x03


i = (i & (1 << 11)) ? 3 : 5; // ok: if((int)i & C) -> avr's bit-test&skip.
 11c:	8a 81       	ldd	r24, Y+2	; 0x02
 11e:	9b 81       	ldd	r25, Y+3	; 0x03
 120:	93 ff       	sbrs	r25, 3
 122:	03 c0       	rjmp	.+6      	; 0x12a <main+0x64>
 124:	83 e0       	ldi	r24, 0x03	; 3
 126:	90 e0       	ldi	r25, 0x00	; 0
 128:	02 c0       	rjmp	.+4      	; 0x12e <main+0x68>
 12a:	85 e0       	ldi	r24, 0x05	; 5
 12c:	90 e0       	ldi	r25, 0x00	; 0
 12e:	8a 83       	std	Y+2, r24	; 0x02
 130:	9b 83       	std	Y+3, r25	; 0x03

i = (i & (1 << 11)) ? 1 : 0; // poor: if((int)i & C) -> if(((int)i >> C') & 1).
 132:	8a 81       	ldd	r24, Y+2	; 0x02
 134:	9b 81       	ldd	r25, Y+3	; 0x03
 136:	89 2f       	mov	r24, r25
 138:	99 27       	eor	r25, r25
 13a:	86 95       	lsr	r24
 13c:	86 95       	lsr	r24
 13e:	86 95       	lsr	r24
 140:	81 70       	andi	r24, 0x01	; 1
 142:	90 70       	andi	r25, 0x00	; 0
 144:	8a 83       	std	Y+2, r24	; 0x02
 146:	9b 83       	std	Y+3, r25	; 0x03


if (i & (1 << 11)) // ok: if((int)i & C) -> avr's bit-test&skip.
 148:	8a 81       	ldd	r24, Y+2	; 0x02
 14a:	9b 81       	ldd	r25, Y+3	; 0x03
 14c:	93 ff       	sbrs	r25, 3
 14e:	03 c0       	rjmp	.+6      	; 0x156 <main+0x90>
     i = 3;
 150:	83 e0       	ldi	r24, 0x03	; 3
 152:	90 e0       	ldi	r25, 0x00	; 0
 154:	02 c0       	rjmp	.+4      	; 0x15a <main+0x94>
else i = 5;
 156:	85 e0       	ldi	r24, 0x05	; 5
 158:	90 e0       	ldi	r25, 0x00	; 0
 15a:	8a 83       	std	Y+2, r24	; 0x02
 15c:	9b 83       	std	Y+3, r25	; 0x03
  
if (i & (1 << 11)) // poor: if((int)i & C) -> avr's bit-test&skip, but w/ineffecient return value.
 15e:	8a 81       	ldd	r24, Y+2	; 0x02
 160:	9b 81       	ldd	r25, Y+3	; 0x03
 162:	9c 01       	movw	r18, r24
 164:	20 70       	andi	r18, 0x00	; 0
 166:	38 70       	andi	r19, 0x08	; 8
 168:	93 ff       	sbrs	r25, 3
 16a:	05 c0       	rjmp	.+10     	; 0x176 <main+0xb0>
     i = 1;
 16c:	81 e0       	ldi	r24, 0x01	; 1
 16e:	90 e0       	ldi	r25, 0x00	; 0
 170:	8a 83       	std	Y+2, r24	; 0x02
 172:	9b 83       	std	Y+3, r25	; 0x03
 174:	02 c0       	rjmp	.+4      	; 0x17a <main+0xb4>
else i = 0;
 176:	2a 83       	std	Y+2, r18	; 0x02
 178:	3b 83       	std	Y+3, r19	; 0x03



/* long tests */

l = (l & ((long)1 << 27)); // ok: ((long)l & C)
 17a:	8c 81       	ldd	r24, Y+4	; 0x04
 17c:	9d 81       	ldd	r25, Y+5	; 0x05
 17e:	ae 81       	ldd	r26, Y+6	; 0x06
 180:	bf 81       	ldd	r27, Y+7	; 0x07
 182:	80 70       	andi	r24, 0x00	; 0
 184:	90 70       	andi	r25, 0x00	; 0
 186:	a0 70       	andi	r26, 0x00	; 0
 188:	b8 70       	andi	r27, 0x08	; 8
 18a:	8c 83       	std	Y+4, r24	; 0x04
 18c:	9d 83       	std	Y+5, r25	; 0x05
 18e:	ae 83       	std	Y+6, r26	; 0x06
 190:	bf 83       	std	Y+7, r27	; 0x07


l = (l & ((long)1 << 27)) ? 3 : 5; // ok: if((long)l & C) -> avr's bit-test&skip.
 192:	8c 81       	ldd	r24, Y+4	; 0x04
 194:	9d 81       	ldd	r25, Y+5	; 0x05
 196:	ae 81       	ldd	r26, Y+6	; 0x06
 198:	bf 81       	ldd	r27, Y+7	; 0x07
 19a:	b3 ff       	sbrs	r27, 3
 19c:	05 c0       	rjmp	.+10     	; 0x1a8 <main+0xe2>
 19e:	83 e0       	ldi	r24, 0x03	; 3
 1a0:	90 e0       	ldi	r25, 0x00	; 0
 1a2:	a0 e0       	ldi	r26, 0x00	; 0
 1a4:	b0 e0       	ldi	r27, 0x00	; 0
 1a6:	04 c0       	rjmp	.+8      	; 0x1b0 <main+0xea>
 1a8:	85 e0       	ldi	r24, 0x05	; 5
 1aa:	90 e0       	ldi	r25, 0x00	; 0
 1ac:	a0 e0       	ldi	r26, 0x00	; 0
 1ae:	b0 e0       	ldi	r27, 0x00	; 0
 1b0:	8c 83       	std	Y+4, r24	; 0x04
 1b2:	9d 83       	std	Y+5, r25	; 0x05
 1b4:	ae 83       	std	Y+6, r26	; 0x06
 1b6:	bf 83       	std	Y+7, r27	; 0x07

l = (l & ((long)1 << 27)) ? 1 : 0; // poor: if((long)l & C) -> if(((long)l >> C') & 1).
 1b8:	8c 81       	ldd	r24, Y+4	; 0x04
 1ba:	9d 81       	ldd	r25, Y+5	; 0x05
 1bc:	ae 81       	ldd	r26, Y+6	; 0x06
 1be:	bf 81       	ldd	r27, Y+7	; 0x07
 1c0:	2b e1       	ldi	r18, 0x1B	; 27
 1c2:	b6 95       	lsr	r27
 1c4:	a7 95       	ror	r26
 1c6:	97 95       	ror	r25
 1c8:	87 95       	ror	r24
 1ca:	2a 95       	dec	r18
 1cc:	d1 f7       	brne	.-12     	; 0x1c2 <main+0xfc>
 1ce:	aa 27       	eor	r26, r26
 1d0:	97 fd       	sbrc	r25, 7
 1d2:	a0 95       	com	r26
 1d4:	ba 2f       	mov	r27, r26
 1d6:	81 70       	andi	r24, 0x01	; 1
 1d8:	90 70       	andi	r25, 0x00	; 0
 1da:	a0 70       	andi	r26, 0x00	; 0
 1dc:	b0 70       	andi	r27, 0x00	; 0
 1de:	8c 83       	std	Y+4, r24	; 0x04
 1e0:	9d 83       	std	Y+5, r25	; 0x05
 1e2:	ae 83       	std	Y+6, r26	; 0x06
 1e4:	bf 83       	std	Y+7, r27	; 0x07


if (l & ((long)1 << 27)) // ok: if((long)l & C) -> avr's bit-test&skip.
 1e6:	8c 81       	ldd	r24, Y+4	; 0x04
 1e8:	9d 81       	ldd	r25, Y+5	; 0x05
 1ea:	ae 81       	ldd	r26, Y+6	; 0x06
 1ec:	bf 81       	ldd	r27, Y+7	; 0x07
 1ee:	b3 ff       	sbrs	r27, 3
 1f0:	05 c0       	rjmp	.+10     	; 0x1fc <main+0x136>
     l = 3;
 1f2:	83 e0       	ldi	r24, 0x03	; 3
 1f4:	90 e0       	ldi	r25, 0x00	; 0
 1f6:	a0 e0       	ldi	r26, 0x00	; 0
 1f8:	b0 e0       	ldi	r27, 0x00	; 0
 1fa:	04 c0       	rjmp	.+8      	; 0x204 <main+0x13e>
else l = 5;
 1fc:	85 e0       	ldi	r24, 0x05	; 5
 1fe:	90 e0       	ldi	r25, 0x00	; 0
 200:	a0 e0       	ldi	r26, 0x00	; 0
 202:	b0 e0       	ldi	r27, 0x00	; 0
 204:	8c 83       	std	Y+4, r24	; 0x04
 206:	9d 83       	std	Y+5, r25	; 0x05
 208:	ae 83       	std	Y+6, r26	; 0x06
 20a:	bf 83       	std	Y+7, r27	; 0x07

if (l & ((long)1 << 27)) // poor: if((long)l & C) -> avr's bit-test&skip, but w/ineffecient return value.
 20c:	8c 81       	ldd	r24, Y+4	; 0x04
 20e:	9d 81       	ldd	r25, Y+5	; 0x05
 210:	ae 81       	ldd	r26, Y+6	; 0x06
 212:	bf 81       	ldd	r27, Y+7	; 0x07
 214:	9c 01       	movw	r18, r24
 216:	ad 01       	movw	r20, r26
 218:	20 70       	andi	r18, 0x00	; 0
 21a:	30 70       	andi	r19, 0x00	; 0
 21c:	40 70       	andi	r20, 0x00	; 0
 21e:	58 70       	andi	r21, 0x08	; 8
 220:	b3 ff       	sbrs	r27, 3
 222:	09 c0       	rjmp	.+18     	; 0x236 <main+0x170>
     l = 1;
 224:	81 e0       	ldi	r24, 0x01	; 1
 226:	90 e0       	ldi	r25, 0x00	; 0
 228:	a0 e0       	ldi	r26, 0x00	; 0
 22a:	b0 e0       	ldi	r27, 0x00	; 0
 22c:	8c 83       	std	Y+4, r24	; 0x04
 22e:	9d 83       	std	Y+5, r25	; 0x05
 230:	ae 83       	std	Y+6, r26	; 0x06
 232:	bf 83       	std	Y+7, r27	; 0x07
 234:	04 c0       	rjmp	.+8      	; 0x23e <main+0x178>
else l = 0;
 236:	2c 83       	std	Y+4, r18	; 0x04
 238:	3d 83       	std	Y+5, r19	; 0x05
 23a:	4e 83       	std	Y+6, r20	; 0x06
 23c:	5f 83       	std	Y+7, r21	; 0x07


return 0;

}

-- 
           Summary: miss-optimization of (x & pow2C) avr conditionals
                    returning bool equivalent values
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         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: avr-unknown-none
  GCC host triplet: powerpc-apple-darwin7.7.0
GCC target triplet: powerpc-apple-darwin7.7.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19154

[Bug c/19154] miss-optimization of (x & pow2C) avr conditionals returning bool equivalent values

[schlie at comcast dot net]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
  GCC build triplet|avr-unknown-none            |powerpc-apple-darwin7.7.0
 GCC target triplet|powerpc-apple-darwin7.7.0   |avr-unknown-none


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19154

[Bug middle-end/19154] miss-optimization of (x & pow2C) avr conditionals returning bool equivalent values

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |minor
          Component|c                           |middle-end
  GCC build triplet|powerpc-apple-darwin7.7.0   |
   GCC host triplet|powerpc-apple-darwin7.7.0   |
           Keywords|                            |missed-optimization


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19154

[Bug middle-end/19154] miss-optimization of (x & pow2C) avr conditionals returning bool equivalent values

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-12-25 20:53 -------
I think the issue here is rtx_cost for avr sucks and does not give a good accurate cost matrix.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19154

[Bug middle-end/19154] miss-optimization of (x & pow2C) avr conditionals returning bool equivalent values

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-12-25 20:57 -------
Take:
char g(char c)
{
return (c & (1 << 3)) != 0;
}

(insn 8 4 30 (set (reg:HI 24 r24 [orig:44 c ] [44])
        (sign_extend:HI (reg:QI 24 r24 [ c ]))) 81 {extendqihi2} (nil)
    (nil))

(insn 30 8 11 (parallel [
            (set (reg:HI 24 r24 [orig:44 c ] [44])
                (lshiftrt:HI (reg:HI 24 r24 [orig:44 c ] [44])
                    (const_int 3 [0x3])))
            (clobber (reg:QI 19 r19))
        ]) 70 {*lshrhi3_const} (nil)
    (expr_list:REG_UNUSED (reg:QI 19 r19)
        (expr_list:REG_UNUSED (reg:QI 25 r25)
            (nil))))

(insn 11 30 12 (set (reg:HI 24 r24 [46])
        (sign_extend:HI (reg:QI 24 r24 [47]))) 81 {extendqihi2} (insn_list:REG_DEP_TRUE 10 (nil))
    (nil))
(insn 19 16 25 (parallel [
            (set (reg/i:HI 24 r24 [ <result> ])
                (and:HI (reg:HI 24 r24 [46])
                    (const_int 1 [0x1])))
            (clobber (scratch:QI))
        ]) 47 {andhi3} (insn_list:REG_DEP_TRUE 11 (nil))
    (expr_list:REG_UNUSED (scratch:QI)
        (nil)))


Which looks good if the rtl matches up one to one per instruction but since avr is not like that we get a 
werid interaction.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2004-12-25 20:57:17
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19154

[Bug middle-end/19154] miss-optimization of (x & pow2C) avr conditionals returning bool equivalent values

[schlie at comcast dot net]

------- Additional Comments From schlie at comcast dot net  2004-12-25 21:39 -------
Subject: Re:  miss-optimization of (x & pow2C) avr
 conditionals returning bool equivalent values

> I think the issue here is rtx_cost for avr sucks and does not give a good
> accurate cost matrix.

I considered that, and sure it doesn't help; but the form of the conditional
presented for code generation is actually different in otherwise identical
expressions, therefore implying that it's presumed that:

 if ((x >> C') & 1) 1 else 0;  => ((x >> C') & 1)

Is more efficient than:

 if ((x >> C') & 1) 1 else 0; => if (x & C) 1 else 0;

Which is target specific, and should not be presumed, as for targets which
support bit-test&branch:

 if (x & C) 1 else 0; => bit-test&branch x log2C; return 0; return 1;

Is significantly more efficient than a (multi-bit-shift & 1).

(therefore it doesn't seem proper for such return value dependant
assumptions to be made in a target neutral way)





-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19154

[Bug middle-end/19154] miss-optimization of (x & pow2C) avr conditionals returning bool equivalent values

[schlie at comcast dot net]

------- Additional Comments From schlie at comcast dot net  2004-12-25 21:56 -------
Subject: Re:  miss-optimization of (x & pow2C) avr
 conditionals returning bool equivalent values

I apologize, I'm confused, what are you comparing to what?

(are you using 4.0, which to my knowledge only builds with my
recent proposed patches, unless the problem was fixed otherwise?)

- to my understanding, (x & C) should never result in ((x >> C') & 1)
  presented to the backend, as it's purely a target specific optimization.


> From: pinskia at gcc dot gnu dot org <gcc-bugzilla@gcc.gnu.org>
> ------- Additional Comments From pinskia at gcc dot gnu dot org  2004-12-25
> 20:57 -------
> Take:
> char g(char c)
> {
> return (c & (1 << 3)) != 0;
> }
> 
> (insn 8 4 30 (set (reg:HI 24 r24 [orig:44 c ] [44])
>         (sign_extend:HI (reg:QI 24 r24 [ c ]))) 81 {extendqihi2} (nil)
>     (nil))
> 
> (insn 30 8 11 (parallel [
>             (set (reg:HI 24 r24 [orig:44 c ] [44])
>                 (lshiftrt:HI (reg:HI 24 r24 [orig:44 c ] [44])
>                     (const_int 3 [0x3])))
>             (clobber (reg:QI 19 r19))
>         ]) 70 {*lshrhi3_const} (nil)
>     (expr_list:REG_UNUSED (reg:QI 19 r19)
>         (expr_list:REG_UNUSED (reg:QI 25 r25)
>             (nil))))
> 
> (insn 11 30 12 (set (reg:HI 24 r24 [46])
>         (sign_extend:HI (reg:QI 24 r24 [47]))) 81 {extendqihi2}
> (insn_list:REG_DEP_TRUE 10 (nil))
>     (nil))
> (insn 19 16 25 (parallel [
>             (set (reg/i:HI 24 r24 [ <result> ])
>                 (and:HI (reg:HI 24 r24 [46])
>                     (const_int 1 [0x1])))
>             (clobber (scratch:QI))
>         ]) 47 {andhi3} (insn_list:REG_DEP_TRUE 11 (nil))
>     (expr_list:REG_UNUSED (scratch:QI)
>         (nil)))
> 
> 
> Which looks good if the rtl matches up one to one per instruction but since
> avr is not like that we get a
> werid interaction.
> 
> -- 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>              Status|UNCONFIRMED                 |NEW
>      Ever Confirmed|                            |1
>    Last reconfirmed|0000-00-00 00:00:00         |2004-12-25 20:57:17
>                date|                            |
> 
> 
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19154
> 
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.




-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19154

[Bug middle-end/19154] miss-optimization of (x & pow2C) avr conditionals returning bool equivalent values

[jackie.rosen at hushmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19154

Jackie Rosen <jackie.rosen at hushmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jackie.rosen at hushmail dot com

--- Comment #11 from Jackie Rosen <jackie.rosen at hushmail dot com> ---
*** Bug 260998 has been marked as a duplicate of this bug. ***
Seen from the domain http://volichat.com
Page where seen: http://volichat.com/adult-chat-rooms
Marked for reference. Resolved as fixed @bugzilla.

[Bug middle-end/19154] miss-optimization of (x & pow2C) avr conditionals returning bool equivalent values

[eric dot weddington at atmel dot com]

------- Comment #10 from eric dot weddington at atmel dot com  2010-01-29 17:12 -------
Setting Target Milestone.


-- 

eric dot weddington at atmel dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19154

[Bug middle-end/19154] miss-optimization of (x & pow2C) avr conditionals returning bool equivalent values

[hutchinsonandy at gcc dot gnu dot org]

------- Comment #9 from hutchinsonandy at gcc dot gnu dot org  2009-12-30 16:14 -------
Fixed on 4.5  - or at least significantly better enough to warrant closure.


-- 

hutchinsonandy at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19154

[Bug middle-end/19154] miss-optimization of (x & pow2C) avr conditionals returning bool equivalent values

[hutchinsonandy at gcc dot gnu dot org]

------- Comment #8 from hutchinsonandy at gcc dot gnu dot org  2009-10-24 15:39 -------
Subject: Bug 19154

Author: hutchinsonandy
Date: Sat Oct 24 15:39:23 2009
New Revision: 153531

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=153531
Log:
        PR middle-end/19154
* avr.md (QIDI): Add new mode iterator.
(sbrx_branch<mode>): Create new zero extract bit, test and jump
patterns for all QI-DI modes combinations.
(sbrx_and_branch<mode>): Create new and based bit test and jump
patterns for QI-SI modes.
avr.c (avr_out_sbxx_branch): Use only bit number.

Modified:
    trunk/gcc/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19154

[Bug middle-end/19154] miss-optimization of (x & pow2C) avr conditionals returning bool equivalent values

[hutchinsonandy at gcc dot gnu dot org]

------- Comment #7 from hutchinsonandy at gcc dot gnu dot org  2009-10-24 15:36 -------
Subject: Bug 19154

Author: hutchinsonandy
Date: Sat Oct 24 15:36:40 2009
New Revision: 153530

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=153530
Log:
PR middle-end/19154
* avr.md (QIDI): Add new mode iterator.
(sbrx_branch<mode>): Create new zero extract bit, test and jump
patterns for all QI-DI modes combinations.
(sbrx_and_branch<mode>): Create new and based bit test and jump
patterns for QI-SI modes.
avr.c (avr_out_sbxx_branch): Use only bit number.

Modified:
    trunk/gcc/config/avr/avr.c
    trunk/gcc/config/avr/avr.md


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19154

[Bug middle-end/19154] miss-optimization of (x & pow2C) avr conditionals returning bool equivalent values

[a dot kaiser at gmx dot net]

------- Comment #6 from a dot kaiser at gmx dot net  2008-05-29 17:01 -------
In a similar case I've got the impression that the ifcombine pass might be
responsible for rewriting the "if" into shift and mask. It is rather
questionable whether this really optimizes things for simple targets which jump
faster as they can shift.

I am suprised however, that many optimization strategies can be disabled by
some -fxxx option, but not this one. A first and probably simple approach could
be, to just add such an option.


-- 

a dot kaiser at gmx dot net changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |a dot kaiser at gmx dot net


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19154