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Re: gcc 4.5.1 / as 2.20.51.0.11 miscompiling drivers/char/i8k.c ?
On Mon, Nov 15, 2010 at 11:54:46AM +0100, Andi Kleen wrote:
> > And for this the starting point should be what has been requested,
> > i.e. preprocessed source + gcc options + gcc version and some hints what
> > actually misbehaves (with the , "+m" (*regs) change reverted)
> > in gcc bugzilla. Only with that we can actually look at what has been
> > happening, see whether it is the tree optimizations or RTL and which one
> > makes a difference.
> > If I've missed a PR about this I apologize.
>
> I tried to file one, but I can't reproduce it currently
> (I don't have hardware, so have to rely on code reading and the 32bit
> code looks correct to me even without the additional +m)
>
> The preprocessed source is at
> http://halobates.de/tmp/i8k.i
>
> Options I used:
>
> -D__KERNEL__ -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -Wno-format-security -fno-delete-null-pointer-checks -O2 -m32 -msoft-float -mregparm=3 -freg-struct-return -mpreferred-stack-boundary=2 -march=i686 -mtune=pentium3 -mtune=generic -maccumulate-outgoing-args -Wa,-mtune=generic32 -ffreestanding -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1 -DCONFIG_AS_CFI_SECTIONS=1 -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -Wframe-larger-than=2048 -fno-stack-protector -fno-omit-frame-pointer -fno-optimize-sibling-calls -pg -Wdeclaration-after-statement -Wno-pointer-sign -fno-strict-overflow -fconserve-stack
Indeed, with this and 4.5.2 20101111 (prerelease) from SVN as well as
gcc-4.5.1-5.fc14:
...
movl %eax, -16(%ebp) # regs, %sfp
movl (%eax), %eax # regs_2(D)->eax,
movl %eax, -20(%ebp) #, %sfp
movl -16(%ebp), %eax # %sfp,
#APP
# 149 "/home/lsrc/git/linux-work2/drivers/char/i8k.c" 1
...
#NO_APP
testl %eax, %eax #
movl $-22, %edx #, D.18378
movl %eax, -24(%ebp) #, %sfp
je .L7 #,
.L2:
movl -12(%ebp), %ebx #,
movl %edx, %eax # D.18378,
movl -8(%ebp), %esi #,
movl -4(%ebp), %edi #,
movl %ebp, %esp #,
popl %ebp #
ret
.p2align 4,,7
.p2align 3
.L7:
movl -16(%ebp), %eax # %sfp,
movl (%eax), %ecx # regs_2(D)->eax, D.18371
cmpw $-1, %cx #, D.18371
je .L2 #,
cmpl %ecx, -20(%ebp) # D.18371, %sfp
cmovne -24(%ebp), %edx # %sfp,, D.18378
jmp .L2 #
.size i8k_smm, .-i8k_smm
I don't see any problems on the assembly level. i8k_smm is
not inlined in this case and checks all 3 conditions.
Guess we need somebody who actually reported the problem, state what
gcc was actually used and post preprocessed source, gcc options
from his case.
Jakub