| Issue |
97956
|
| Summary |
DSE removes store before free() incorrectly
|
| Labels |
miscompilation,
llvm:optimizations
|
| Assignees |
|
| Reporter |
nunoplopes
|
TL;DR: the transformation below needs gep inbounds, otherwise the input ptr may have a negative offset.
```llvm
; test/Transforms/DeadStoreElimination/free.ll
define void @test2(ptr %P) {
%Q = gep ptr %P, 8 x i32 0, 1 x i64 4
store i32 4, ptr %Q, align 4
call void @free(ptr %P) alloc-family(malloc) allockind(free)
ret void
}
=>
define void @test2(ptr %P) {
call void @free(ptr %P) alloc-family(malloc)
ret void
}
Transformation doesn't verify!
ERROR: Mismatch in memory
Example:
ptr %P = pointer(non-local, block_id=1, offset=-4) / Address=#x000
Source:
ptr %Q = pointer(non-local, block_id=1, offset=0) / Address=#x004
Function @free returned
SOURCE MEMORY STATE
===================
NON-LOCAL BLOCKS:
Block 0 > size: 0 align: 4 alloc type: 0 alive: false address: 0
Block 1 > size: 9 align: 1 alloc type: 0 alive: true address: 4
Target:
Function @free returned
Mismatch in pointer(non-local, block_id=1, offset=0)
Source value: #x00000004
Target value: poison
```
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