| Issue |
98434
|
| Summary |
Wrong splatting condition of vector select by InstCombine
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
bonjune
|
https://github.com/llvm/llvm-project/blob/7eae9bb856135136cddc4208a2b1546e9db44c9c/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp#L3568-L3569
Alive2 report: https://alive2.llvm.org/ce/z/G66ZVg
```ll
----------------------------------------
define <2 x i16> @fun0(<1 x i1> %val0, <1 x i32> %val1, <4 x i1> %val2) {
entry:
%val3 = extractelement <4 x i1> %val2, i32 3
%val4 = select i1 %val3, <2 x i16> { 0, 0 }, <2 x i16> { 65535, 65535 }
ret <2 x i16> %val4
}
=>
define <2 x i16> @fun0(<1 x i1> %val0, <1 x i32> %val1, <4 x i1> %val2) {
entry:
%.splat = shufflevector <4 x i1> %val2, <4 x i1> poison, 3, 3
%not..splat = xor <2 x i1> %.splat, { 1, 1 }
%val4 = sext <2 x i1> %not..splat to <2 x i16>
ret <2 x i16> %val4
}
Transformation doesn't verify!
ERROR: Value mismatch
Example:
<1 x i1> %val0 = < poison >
<1 x i32> %val1 = < poison >
<4 x i1> %val2 = < poison, poison, poison, undef >
Source:
i1 %val3 = #x0 (0) [based on undef value]
<2 x i16> %val4 = < #xffff (65535, -1), #xffff (65535, -1) >
Target:
<2 x i1> %.splat = < #x0 (0), #x1 (1) >
<2 x i1> %not..splat = < #x1 (1), #x0 (0) >
<2 x i16> %val4 = < #xffff (65535, -1), #x0000 (0) >
Source value: < #xffff (65535, -1), #xffff (65535, -1) >
Target value: < #xffff (65535, -1), #x0000 (0) >
Summary:
0 correct transformations
1 incorrect transformations
0 failed-to-prove transformations
0 Alive2 errors
```
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