| Issue |
97702
|
| Summary |
[SROA] Incorrect poison propagation
|
| Labels |
miscompilation,
llvm:optimizations
|
| Assignees |
|
| Reporter |
nikic
|
```llvm
; RUN: opt -S -passes=sroa < %a
define i8 @test(i1 %cond) {
start:
%a = alloca i8, align 1
br i1 %cond, label %bb1, label %bb2
bb1:
store i8 poison, ptr %a, align 1
br label %exit
bb2:
br label %exit
exit:
%5 = load i8, ptr %a, align 1
ret i8 %5
}
```
Results in:
```llvm
define i8 @test(i1 %cond) {
br i1 %cond, label %bb1, label %bb2
bb1: ; preds = %start
br label %exit
bb2: ; preds = %start
br label %exit
exit: ; preds = %bb2, %bb1
ret i8 poison
}
```
This is incorrect. If `%cond` is false, then the result must be undef, not poison.
The original test case is more along these lines (not sure yet whether the root cause is always the same):
```llvm
define i24 @test(i1 %cond) {
start:
%a = alloca [3 x i8], align 1
%b = alloca [1 x i8], align 1
%a.1 = getelementptr inbounds i8, ptr %a, i64 1
store i8 1, ptr %a, align 1
store i8 1, ptr %a.1, align 1
br i1 %cond, label %bb1, label %bb2
bb1:
%b.1 = getelementptr inbounds i8, ptr %b, i64 1
%oob = load i8, ptr %b.1, align 1
%a.2 = getelementptr inbounds i8, ptr %a, i64 2
store i8 %oob, ptr %a.2, align 1
br label %exit
bb2:
br label %exit
exit:
%5 = load i24, ptr %a, align 1
ret i24 %5
}
```
![]()
_______________________________________________
llvm-bugs mailing list
[email protected]
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
