| Issue |
113863
|
| Summary |
Wrong folding a binary operator into PHI
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
bongjunj
|
https://github.com/llvm/llvm-project/blob/d3f70db51cbc0876937d404e96fbda04df793bd4/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp#L2023-L2035
Alive2 report: https://alive2.llvm.org/ce/z/tbFHc3
```llvm
----------------------------------------
define i64 @constant_range_and_undef2.2(i1 %c1, i1 %c2, i64 %a) {
entry:
br i1 %c1, label %bb1, label %bb2
bb2:
%v2 = and i64 %a, 4294967295
br label %bb3
bb1:
br label %bb3
bb3:
%p = phi i64 [ poison, %bb1 ], [ %v2, %bb2 ]
br i1 %c2, label %bb4, label %bb5
bb4:
br label %bb6
bb5:
br label %bb6
bb6:
%p2 = phi i64 [ %p, %bb4 ], [ undef, %bb5 ]
%res = and i64 %p2, 255
ret i64 %res
}
=>
define i64 @constant_range_and_undef2.2(i1 %c1, i1 %c2, i64 %a) {
entry:
br i1 %c1, label %bb1, label %bb2
bb2:
%#0 = and i64 %a, 255
br label %bb3
bb1:
br label %bb3
bb3:
%p = phi i64 [ poison, %bb1 ], [ %#0, %bb2 ]
br i1 %c2, label %bb4, label %bb5
bb4:
br label %bb6
bb5:
br label %bb6
bb6:
ret i64 %p
}
Transformation doesn't verify!
ERROR: Target is more poisonous than source
Example:
i1 %c1 = #x1 (1)
i1 %c2 = #x0 (0)
i64 %a = #x0000000000000000 (0)
Source:
>> Jump to %bb1
>> Jump to %bb3
i64 %p = poison
>> Jump to %bb5
>> Jump to %bb6
i64 %p2 = #x0000000000000000 (0) [based on undef value]
i64 %res = #x0000000000000000 (0)
Target:
>> Jump to %bb1
>> Jump to %bb3
i64 %p = poison
>> Jump to %bb5
>> Jump to %bb6
Source value: #x0000000000000000 (0)
Target value: poison
Summary:
0 correct transformations
1 incorrect transformations
0 failed-to-prove transformations
0 Alive2 errors
```
![]()
_______________________________________________
llvm-bugs mailing list
[email protected]
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
