http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11261
Oleg Endo <olegendo at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |olegendo at gcc dot gnu.org
--- Comment #6 from Oleg Endo <olegendo at gcc dot gnu.org> 2012-07-22 14:54:11
UTC ---
As of rev 189746 the issue is still present.
With '-m4-single -O2 -mpretend-cmove' (scheduling disabled by default) the file
jidctflt.c from the CSiBE set contains the following sequence:
...
sts fpul,r0
ftrc fr7,fpul
add #4,r0
shad r6,r0
and r7,r0
mov.b @(r0,r2),r0
mov.b r0,@(1,r1)
sts fpul,r0
ftrc fr1,fpul
fmov fr5,fr1
fadd fr2,fr1
fsub fr2,fr5
add #4,r0
shad r6,r0
and r7,r0
mov.b @(r0,r2),r0
mov.b r0,@(6,r1)
sts fpul,r0
ftrc fr6,fpul
add #4,r0
shad r6,r0
and r7,r0
mov.b @(r0,r2),r0
mov.b r0,@(2,r1)
sts fpul,r0
ftrc fr1,fpul
add #4,r0
shad r6,r0
and r7,r0
mov.b @(r0,r2),r0
mov.b r0,@(5,r1)
sts fpul,r0
....
With '-m4-single -O2 -mpretend-cmove -fschedule-insns' it seems to be better.
The address index is calculated in different regs than R0 and then copied to
R0, as described in comment #5:
ftrc fr7,fpul
mov r11,r0
sts fpul,r5
fadd fr3,fr1
mov.b @(r0,r2),r0
add #4,r4
fmov fr10,fr0
fmac fr0,fr11,fr2
shad r6,r4
mov.b r0,@(7,r1)
and r7,r4
ftrc fr1,fpul
mov r4,r0
fadd fr3,fr2
mov.b @(r0,r2),r0
add #4,r5
sts fpul,r4
fsub fr3,fr6
shad r6,r5
mov.b r0,@(1,r1)
and r7,r5
fmov fr5,fr1
ftrc fr6,fpul
mov r5,r0
sts fpul,r11
add #4,r4
mov.b @(r0,r2),r0
fadd fr2,fr1
shad r6,r4
fsub fr2,fr5
mov.b r0,@(6,r1)
and r7,r4
mov r4,r0
ftrc fr1,fpul
mov.b @(r0,r2),r0
add #4,r11
sts fpul,r4
shad r6,r11
mov.b r0,@(2,r1)
Thus, for this case it might be beneficial to enable sched1 again.
Although, looking at some recent sched1 vs. no-sched1 runtime numbers in PR
22553, sched1 it doesn't seem to make a big difference on average.
