Created attachment 469 [details]
bugpoint reduced testcase

Miscompile. If you need any more information (like the llc generated .s) just
ask.

Created attachment 470 [details]
matching x86 assembly

Ah, it's small. Attaching the asm.

Nick,

I was getting something similar until I updated my CFE this morning. Did you
update your CFE and rebuild?

Reid.

No, I rebuilt it right before building LLVM. I try to have a working LLVM before
building the CFE.

I'll try it now.

No change.

Builds and tests okay here. Dunno.

Reduced testcase:

float %foo(float *%col.2.0) {
        %tmp = load float* %col.2.0             ; <float> [#uses=3]
        %tmp16 = setlt float %tmp, 0.000000e+00         ; <bool> [#uses=1]
        %tmp20 = sub float -0.000000e+00, %tmp          ; <float> [#uses=1]
        %iftmp.2.0 = select bool %tmp16, float %tmp20, float %tmp
        ret float %iftmp.2.0
}

compiles to:

$ llvm-as < t.ll | llc -mcpu=i386
_foo:
        movl 4(%esp), %eax
        flds (%eax)
        fld %st(0)
        fchs
        fldz
        fucomip %st(0), %st(0)
        fxch %st(1)
        fcmovnbe %st(1), %st(0)
        fstp %st(1)
        #FP_REG_KILL
        ret

Note that the fucomip compares two zeros against each other.  This is probably fallout from Evan's 
recent patch.

-Chris

Fixed.  Testcase here: CodeGen/X86/fp-stack-compare.ll
Patch here:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20061120/040133.html
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20061120/040134.html

-Chris