| Issue |
89516
|
| Summary |
miscompile of vanilla integer code by InstCombine
|
| Labels |
miscompilation,
llvm:instcombine
|
| Assignees |
|
| Reporter |
regehr
|
https://alive2.llvm.org/ce/z/jRfVLr
this function:
```llvm
define i8 @f(i8 %0, i8 %1) {
%3 = icmp slt i8 %1, 0
%4 = shl i8 1, %0
%5 = srem i8 1, %4
%6 = add i8 %5, %4
%7 = select i1 %3, i8 %6, i8 %5
ret i8 %7
}
```
is getting mis-optimized to:
```llvm
define i8 @f(i8 %0, i8 %1) {
%3 = icmp ne i8 %0, 0
%4 = zext i1 %3 to i8
ret i8 %4
}
```
here I'll just give Alive's work:
```
Example:
i8 %#0 = #x00 (0)
i8 %#1 = #xff (255, -1)
Source:
i1 %#3 = #x1 (1)
i8 %#4 = #x01 (1)
i8 %#5 = #x00 (0)
i8 %#6 = #x01 (1)
i8 %#7 = #x01 (1)
Target:
i1 %#3 = #x0 (0)
i8 %#4 = #x00 (0)
Source value: #x01 (1)
Target value: #x00 (0)
```
cc @nunoplopes @hatsunespica
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