| Issue |
113862
|
| Summary |
Wrong folding `and` of `icmp`s on undefined values
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
bongjunj
|
https://github.com/llvm/llvm-project/blob/d3f70db51cbc0876937d404e96fbda04df793bd4/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp#L2747-L2754
Alive2 report: https://alive2.llvm.org/ce/z/MYjDiS
```llvm
----------------------------------------
define i1 @bitwise_and_bitwise_and_icmps_comm1.2(i8 %x, i8 %y, i8 %z, ptr %#0) {
#1:
%c1 = icmp eq i8 %y, 42
%x.m1 = and i8 %x, 1
%#2 = zext i1 %c1 to i8
%z.shift = shl i8 1, %#2
%x.m2 = and i8 %x, %z.shift
%c2 = icmp ne i8 %x.m1, 0
%c3 = icmp ne i8 %x.m2, 0
%#3 = and i1 1, 1
%and1 = and i1 %#3, %c2
%and2 = and i1 %c3, %and1
ret i1 %and2
}
=>
define i1 @bitwise_and_bitwise_and_icmps_comm1.2(i8 %x, i8 %y, i8 %z, ptr %#0) {
#1:
%c1 = icmp eq i8 %y, 42
%#2 = zext i1 %c1 to i8
%z.shift = shl nsw nuw i8 1, %#2
%#3 = or i8 %z.shift, 1
%#4 = and i8 %x, %#3
%and2 = icmp eq i8 %#4, %#3
ret i1 %and2
}
Transformation doesn't verify!
ERROR: Target's return value is more undefined
Example:
i8 %x = #x03 (3)
i8 %y = undef
i8 %z = #x00 (0) [based on undef value]
ptr %#0 = null [based on undef value]
Source:
i1 %c1 = #x0 (0) [based on undef value]
i8 %x.m1 = #x01 (1)
i8 %#2 = #x00 (0)
i8 %z.shift = #x01 (1)
i8 %x.m2 = #x01 (1)
i1 %c2 = #x1 (1)
i1 %c3 = #x1 (1)
i1 %#3 = #x1 (1)
i1 %and1 = #x1 (1)
i1 %and2 = #x1 (1)
SOURCE MEMORY STATE
===================
NON-LOCAL BLOCKS:
Block 0 > size: 0 align: 1 alloc type: 0 alive: false address: 0
Block 1 > size: 4 align: 1 alloc type: 0 alive: true address: 1
Target:
i1 %c1 = #x1 (1)
i8 %#2 = #x01 (1)
i8 %z.shift = #x02 (2)
i8 %#3 = #x03 (3)
i8 %#4 = #x03 (3)
i1 %and2 = #x0 (0)
Source value: #x1 (1)
Target value: #x0 (0)
Summary:
0 correct transformations
1 incorrect transformations
0 failed-to-prove transformations
0 Alive2 errors
```
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