| Issue |
139041
|
| Summary |
Wrong `select (fcmp ...) (fadd ...)` folding to llvm max intrinsic
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
bongjunj
|
```llvm
define float @test_fcmp_ogt_fadd_select_rewrite_and_fastmath.2(float %in) {
%cmp1 = fcmp nnan ogt float %in, 0.000000e+00
%2 = fadd float %in, 1.000000e+00
%sel = select fast i1 %cmp1, float %2, float 1.000000e+00
ret float %sel
}
```
```
define float @test_fcmp_ogt_fadd_select_rewrite_and_fastmath(float %in) {
#0:
%cmp1 = fcmp nnan ogt float %in, 0.000000
%add = fadd float %in, 1.000000
%sel = select fast i1 %cmp1, float %add, float 1.000000
ret float %sel
}
=>
define float @test_fcmp_ogt_fadd_select_rewrite_and_fastmath(float %in) {
#0:
%sel = fmax nnan ninf nsz float %in, 0.000000
%add = fadd nnan ninf nsz float %sel, 1.000000
ret float %add
}
Transformation doesn't verify!
ERROR: Target is more poisonous than source
Example:
float %in = #xff800000 (-oo)
Source:
i1 %cmp1 = #x0 (0)
float %add = #xff800000 (-oo)
float %sel = #x00000000 (+0.0)
Target:
float %sel = poison
float %add = poison
Source value: #x00000000 (+0.0)
Target value: poison
Summary:
0 correct transformations
1 incorrect transformations
0 failed-to-prove transformations
0 Alive2 errors
```
While the alive2 site (https://alive2.llvm.org/ce/z/50KuQH) complains that it used approximation so it could not conclude,
I think it may have nothing to do with approximation.
Targeted Commit of Test: https://github.com/llvm/llvm-project/commit/a0c4876eede8e68de22dc5296b037556c7cca981
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