| Issue |
147123
|
| Summary |
[DebugInfo][Float2Int] Erasing the operands of dead instructions without updating debug values
|
| Labels |
question,
debuginfo,
llvm:transforms
|
| Assignees |
|
| Reporter |
Apochens
|
In Float2Int, the optimization deletes the "root" instructions after converting the float-point operations into integer operations.
https://github.com/llvm/llvm-project/blob/0e9571df982fb0527cac2c6a6d21ff502f5d4668/llvm/lib/Transforms/Scalar/Float2Int.cpp#L475-L479
However, the optimization only RAUWs the "root" instructions with the converted instructions:
https://github.com/llvm/llvm-project/blob/0e9571df982fb0527cac2c6a6d21ff502f5d4668/llvm/lib/Transforms/Scalar/Float2Int.cpp#L467-L469
As a result, the debug values of the operands of the RAUWed dead instructions may be lost. Here is an example: https://godbolt.org/z/fqde9nbW4
```llvm
; after optimization
define i16 @simple1(i8 %a) !dbg !5 {
%1 = zext i8 %a to i32, !dbg !14
#dbg_value(float poison, !9, !DIExpression(), !14)
%t21 = add i32 %1, 1, !dbg !15
#dbg_value(float poison, !11, !DIExpression(), !15)
%2 = trunc i32 %t21 to i16, !dbg !16
#dbg_value(i16 %2, !12, !DIExpression(), !16)
ret i16 %2, !dbg !17
}
```
So, in this case, should we use `SalvageDebugInfo` or `replaceAllDbgUses` on these operands?
CC @OCHyams
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