| Issue |
97730
|
| Summary |
Wrong masked merge of vector operands by InstCombine
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
bonjune
|
https://alive2.llvm.org/ce/z/Nws3Yr
```
----------------------------------------
define <4 x i1> @fun0(<4 x i1> %val0, <4 x i1> %val1, <4 x i1> %val2) {
entry:
%val3 = add <4 x i1> %val1, { 1, 1, 1, 1 }
%val4 = xor <4 x i1> { 0, undef, undef, 1 }, %val0
%val5 = and <4 x i1> %val4, %val3
%val6 = sub <4 x i1> %val5, %val0
ret <4 x i1> %val6
}
=>
define <4 x i1> @fun0(<4 x i1> %val0, <4 x i1> %val1, <4 x i1> %val2) nofree willreturn memory(none) {
entry:
%val4 = xor <4 x i1> %val0, { 0, undef, undef, 1 }
%#0 = and <4 x i1> %val4, %val1
%val6 = xor <4 x i1> %#0, { 0, undef, undef, 1 }
ret <4 x i1> %val6
}
Transformation doesn't verify!
ERROR: Target's return value is more undefined
Example:
<4 x i1> %val0 = < #x0 (0), #x0 (0), #x0 (0), #x0 (0) >
<4 x i1> %val1 = < #x0 (0), #x0 (0), #x1 (1), #x0 (0) >
<4 x i1> %val2 = < #x0 (0), #x0 (0), #x0 (0), #x0 (0) >
```
`tgt` produces `<0, undef, undef, 1>` while `src` produces `<0, 0, undef, 1>` for the given example input.
This breaks refinement relation.
https://github.com/llvm/llvm-project/blob/f329e3ed9070aee3f4c0ebc80ed62f5c4b645d73/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp#L4196-L4201
![]()
_______________________________________________
llvm-bugs mailing list
[email protected]
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
