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* [Bug middle-end/42863] New: [4.5] Regression whith auto increments
@ 2010-01-25 19:34 gcc-bugzilla at gcc dot gnu dot org
2010-01-25 19:45 ` [Bug middle-end/42863] " schwab at linux-m68k dot org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: gcc-bugzilla at gcc dot gnu dot org @ 2010-01-25 19:34 UTC (permalink / raw)
To: gcc-bugs
This is a general m68k code generation regression. Starting with revision
150588 GCC for m68k generates "surprising" code for auto increments, eg.
for a strlcpy implementation. Compiling this code with the 4.5.0 snapshot
from 20100107 yields:
-- 4.5.0 --
_strlcpy:
movel d3,sp@-
movel d2,sp@-
movel sp@(16),d0
movel sp@(20),d1
jeq L7
movel d0,a0
movel sp@(12),a1
L3:
movel a0,d2
subql #1,d1
jeq L11
moveb a0@+,d2
moveb d2,a1@+
movel a0,d3 | <--
tstb d2 | <--
jne L3
L4:
subl d3,d0
notl d0
movel sp@+,d2
movel sp@+,d3
rts
L7:
movel d0,d2
movel d2,a0
L6:
moveb a0@+,d1
movel a0,d3 | <--
tstb d1 | <--
jeq L4
moveb a0@+,d1
movel a0,d3 | <--
tstb d1 | <--
jne L6
jra L4
L11:
clrb a1@
movel d2,a0
jra L6
-- cut --
Suddenly GCC inserts "useless" moves and because of these moves has also
to generate explicit tst instructions. Older GCC versions generated better
code by using tst.b incrementing an address register without extra move
instructions, i.e. 4.4.0:
-- 4.4.0 (release) --
_strlcpy:
movel d2,sp@-
movel sp@(8),a1
movel sp@(12),d0
movel sp@(16),d1
jne L2
movel d0,a0
L8:
tstb a0@+
jne L8
L5:
subl a0,d0
notl d0
movel sp@+,d2
rts
L2:
movel d0,a0
subql #1,d1
jeq L11
L6:
moveb a0@+,d2
moveb d2,a1@
jeq L5
addql #1,a1
subql #1,d1
jne L6
L11:
clrb a1@
tstb a0@+
jne L8
jra L5
-- cut --
Environment:
System: FreeBSD 6.3-STABLE #0: Sat Mar 1 11:12:32 CET 2008
root@sirius:/usr/obj/usr/src/sys/SIRIUS i386
host: i386-unknown-freebsd6.3
build: i386-unknown-freebsd6.3
target: m68k-unknown-amigaos
configured with: ../gcc-4.5-gg/configure --disable-nls --disable-libssp
--enable-languages=c --with-gmp=/usr/local --disable-tls --target=m68k-amigaos
How-To-Repeat:
Compiling the following code with
gcc-4.5.0 -O2 -fomit-frame-pointer strlcpy.c -o -
demonstrates the problem. FWIW, m68k-elf exhibits the very same problem!
-- cut --
typedef unsigned long size_t;
size_t
strlcpy(char *dst, const char *src, size_t n)
{ const char *s = src;
if (n) {
while (--n)
if ((*dst++ = *s++) == '\0')
goto out;
*dst = '\0';
}
while (*s++ != '\0')
continue;
out:
return ~(src - s);
}
-- cut --
------- Comment #1 from gnikl at users dot sourceforge dot net 2010-01-25 19:34 -------
Fix:
Reverting rev 150588 restores the previous behaviour.
--
Summary: [4.5] Regression whith auto increments
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: gnikl at users dot sourceforge dot net
GCC build triplet: i386-unknown-freebsd6.3
GCC host triplet: i386-unknown-freebsd6.3
GCC target triplet: m68k-unknown-amigaos
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42863
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug middle-end/42863] [4.5] Regression whith auto increments
2010-01-25 19:34 [Bug middle-end/42863] New: [4.5] Regression whith auto increments gcc-bugzilla at gcc dot gnu dot org
@ 2010-01-25 19:45 ` schwab at linux-m68k dot org
2010-01-26 12:10 ` [Bug rtl-optimization/42863] [4.5 Regression] with " rguenth at gcc dot gnu dot org
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: schwab at linux-m68k dot org @ 2010-01-25 19:45 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from schwab at linux-m68k dot org 2010-01-25 19:44 -------
m68k-unknown-amigaos is not a valid target.
--
schwab at linux-m68k dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
GCC build triplet|i386-unknown-freebsd6.3 |
GCC host triplet|i386-unknown-freebsd6.3 |
GCC target triplet|m68k-unknown-amigaos |m68k-elf
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42863
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug rtl-optimization/42863] [4.5 Regression] with auto increments
2010-01-25 19:34 [Bug middle-end/42863] New: [4.5] Regression whith auto increments gcc-bugzilla at gcc dot gnu dot org
2010-01-25 19:45 ` [Bug middle-end/42863] " schwab at linux-m68k dot org
@ 2010-01-26 12:10 ` rguenth at gcc dot gnu dot org
2010-04-06 11:39 ` rguenth at gcc dot gnu dot org
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2010-01-26 12:10 UTC (permalink / raw)
To: gcc-bugs
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|middle-end |rtl-optimization
Keywords| |missed-optimization
Priority|P3 |P4
Summary|[4.5] Regression with auto |[4.5 Regression] with auto
|increments |increments
Target Milestone|--- |4.5.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42863
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug rtl-optimization/42863] [4.5 Regression] with auto increments
2010-01-25 19:34 [Bug middle-end/42863] New: [4.5] Regression whith auto increments gcc-bugzilla at gcc dot gnu dot org
2010-01-25 19:45 ` [Bug middle-end/42863] " schwab at linux-m68k dot org
2010-01-26 12:10 ` [Bug rtl-optimization/42863] [4.5 Regression] with " rguenth at gcc dot gnu dot org
@ 2010-04-06 11:39 ` rguenth at gcc dot gnu dot org
2010-04-07 23:50 ` [Bug rtl-optimization/42863] [4.5/4.6 " hp at gcc dot gnu dot org
2010-07-31 9:33 ` rguenth at gcc dot gnu dot org
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2010-04-06 11:39 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from rguenth at gcc dot gnu dot org 2010-04-06 11:20 -------
GCC 4.5.0 is being released. Deferring to 4.5.1.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|4.5.0 |4.5.1
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42863
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug rtl-optimization/42863] [4.5/4.6 Regression] with auto increments
2010-01-25 19:34 [Bug middle-end/42863] New: [4.5] Regression whith auto increments gcc-bugzilla at gcc dot gnu dot org
` (2 preceding siblings ...)
2010-04-06 11:39 ` rguenth at gcc dot gnu dot org
@ 2010-04-07 23:50 ` hp at gcc dot gnu dot org
2010-07-31 9:33 ` rguenth at gcc dot gnu dot org
4 siblings, 0 replies; 6+ messages in thread
From: hp at gcc dot gnu dot org @ 2010-04-07 23:50 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from hp at gcc dot gnu dot org 2010-04-07 23:50 -------
FWIW, I see similar "useless" register moves for cris-elf (also an
autoincrement port with cc0) on trunk r158090 and 4.5-branch r158099, that
aren't there on the 4.4 branch r158082 (with no changes that matter in
r158096). JFTR, the cc0-clobbering ones are moved by the delayed-branch pass,
but that doesn't matter to m68k. :)
--
hp at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |hp at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42863
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug rtl-optimization/42863] [4.5/4.6 Regression] with auto increments
2010-01-25 19:34 [Bug middle-end/42863] New: [4.5] Regression whith auto increments gcc-bugzilla at gcc dot gnu dot org
` (3 preceding siblings ...)
2010-04-07 23:50 ` [Bug rtl-optimization/42863] [4.5/4.6 " hp at gcc dot gnu dot org
@ 2010-07-31 9:33 ` rguenth at gcc dot gnu dot org
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2010-07-31 9:33 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from rguenth at gcc dot gnu dot org 2010-07-31 09:29 -------
GCC 4.5.1 is being released, adjusting target milestone.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|4.5.1 |4.5.2
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42863
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2010-07-31 9:33 UTC | newest]
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2010-01-25 19:34 [Bug middle-end/42863] New: [4.5] Regression whith auto increments gcc-bugzilla at gcc dot gnu dot org
2010-01-25 19:45 ` [Bug middle-end/42863] " schwab at linux-m68k dot org
2010-01-26 12:10 ` [Bug rtl-optimization/42863] [4.5 Regression] with " rguenth at gcc dot gnu dot org
2010-04-06 11:39 ` rguenth at gcc dot gnu dot org
2010-04-07 23:50 ` [Bug rtl-optimization/42863] [4.5/4.6 " hp at gcc dot gnu dot org
2010-07-31 9:33 ` rguenth at gcc dot gnu dot org
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