matching inline asm constraints with memory not implemented

[llvmbot]

Bugzilla Link	1133
Resolution	FIXED
Resolved on	Feb 20, 2008 23:28
Version	trunk
OS	Linux
Blocks	#1234
Attachments	bugpoint reduction
Reporter	LLVM Bugzilla Contributor
CC	@efriedma-quic

Extended Description

the attched reduction is from code that passes regular gcc.

llc: SelectionDAGISel.cpp:2622: void
llvm::SelectionDAGLowering::visitInlineAsm(llvm::CallInst&): Assertion `(NumOps
& 7) == 2 && "Skipped past definitions?"' failed.

[lattner]

*** Bug llvm/llvm-bugzilla-archive#1490 has been marked as a duplicate of this bug. ***

[lattner]

*** Bug llvm/llvm-bugzilla-archive#1640 has been marked as a duplicate of this bug. ***

[efriedma-quic]

Probably not that useful to comment, but I just ran into this attempting to compile ffmpeg.

[lattner]

Eli, can you include the C source for the inline asm expression that causes the problem?

[efriedma-quic]

code from ffmpeg
Okay, here's the preprocessed source of the relevant function. It's in the file dsputil_mmx_avg.h in ffmpeg/libavcodec.

[efriedma-quic]

Filed Bug 2019... we can work out what's going on with this testcase there.

[lattner]

Reduced testcase here:

int pixels;
int h;

void test() {
__asm __volatile(" %0 %1 %2 %3"
:"+imr"(h), "+S"(pixels)
: :"eax", "memory");
}
void test2() {
__asm __volatile(
" %0 %1 %2 %3"
:"+r"(h), "+S"(pixels)
: :"eax", "memory");
}

llvm-gcc rejects the former, but is fine with the later.

[efriedma-quic]

Hmm, so it is actually this bug... I guess that makes bug 2019 a clang bug.

[efriedma-quic]

Patch
As far as I can tell, this fix is correct. Of course, this should be reviewed by someone familiar with the relevant code.

[lattner]

Your patch looks great to me, applied:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20080218/058625.html

Thanks Eli!

[lattner]

mentioned in issue llvm/llvm-bugzilla-archive#1490

[lattner]

mentioned in issue llvm/llvm-bugzilla-archive#1640

[ggreif]

mentioned in issue llvm/llvm-bugzilla-archive#1682

[asl]

mentioned in issue #1234