| Issue |
161524
|
| Summary |
[InstCombine] Freeze is incorrectly dropped
|
| Labels |
miscompilation,
llvm:instcombine,
generated by fuzzer
|
| Assignees |
dtcxzyw
|
| Reporter |
dtcxzyw
|
Reproducer: https://alive2.llvm.org/ce/z/xyfr4N
```
; bin/opt -passes=instcombine test.ll -S
define float @test(float %arg) {
entry:
%cond = tail call i1 @llvm.is.fpclass.f32(float %arg, i32 144)
%0 = freeze i1 %cond
br i1 %0, label %if.then, label %if.exit
if.then: ; preds = %entry
%fadd = fadd float %arg, 1.0
br label %if.exit
if.exit: ; preds = %if.then, %entry
%ret = phi ninf float [ %fadd, %if.then ], [ %arg, %entry ]
%1 = freeze float %ret
ret float %1
}
```
```
=>
define float @test(float %arg) {
entry:
%arg.fr = freeze float %arg
%cond = is.fpclass float %arg.fr, i32 144
br i1 %cond, label %if.then, label %if.exit
if.then:
%fadd = fadd float %arg.fr, 1.000000
br label %if.exit
if.exit:
%ret = phi ninf float [ %fadd, %if.then ], [ %arg.fr, %entry ]
ret float %ret
}
Transformation doesn't verify!
ERROR: Target is more poisonous than source
Example:
float %arg = #xff800000 (-oo)
Source:
i1 %cond = #x0 (0)
i1 %#0 = #x0 (0)
>> Jump to %if.exit
float %ret = poison
float %#1 = #x00000003 (0.000000000000?)
Target:
float %arg.fr = #xff800000 (-oo)
i1 %cond = #x0 (0)
>> Jump to %if.exit
float %ret = poison
Source value: #x00000003 (0.000000000000?)
Target value: poison
```
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