| Issue |
141538
|
| Summary |
Wrong folding to `fabs`
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
bongjunj
|
Alive2 report: https://alive2.llvm.org/ce/z/iPnYcf
```llvm
----------------------------------------
define float @select_nnan_ninf_nsz_fcmp_nnan_nsz_olt_negzero.2(float %x) {
#0:
%#1 = fcmp oge float %x, -0.000000
%negx = fsub nnan nsz float -0.000000, %x
%fabs = select nnan ninf nsz i1 %#1, float %negx, float %x
%#2 = fabs float %fabs
ret float %#2
}
=>
define float @select_nnan_ninf_nsz_fcmp_nnan_nsz_olt_negzero.2(float %x) nofree willreturn memory(none) {
#0:
%#1 = fabs nnan ninf nsz float %x
ret float %#1
}
Transformation doesn't verify!
ERROR: Value mismatch
Example:
float %x = #x00000000 (+0.0)
Source:
i1 %#1 = #x1 (1)
float %negx = #x00000000 (+0.0)
float %fabs = #x00000000 (+0.0)
float %#2 = #x00000000 (+0.0)
Target:
float %#1 = #x80000000 (-0.0)
Source value: #x00000000 (+0.0)
Target value: #x80000000 (-0.0)
Summary:
0 correct transformations
1 incorrect transformations
0 failed-to-prove transformations
0 Alive2 errors
```
Is it an expected behavior for the signbit to flip?
I think this is introduced recently from https://github.com/llvm/llvm-project/commit/d13947bd6caf442151a4b3f51e3e8b226c490535
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