| Issue |
144300
|
| Summary |
Missed DSE of non-inlineable call
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
qchateau
|
Minimal working example:
```
@x = global i32 0, align 4
define void @bar(ptr %0) noinline {
%2 = load i32, ptr @x, align 4
store i32 %2, ptr %0, align 4
ret void
}
define void @foo() {
%1 = alloca i32, align 4
call void @bar(ptr %1)
ret void
}
```
`@bar` stores the value of global `@x` in its argument. It is marked `noinline`.
`@foo` calls `@bar` with an `alloca` variable, and does nothing else. At `-O3`, opt (trunk) is not able to kill the call to `@bar`.
In practice, I noticed this with an indirect call instead of a call to "@bar", and could not make DSE work as soon as the called function read memory (understand: the call gets DSE'ed with `memory(argmem: readwrite)`, but not with `memory(read, argmem: readwrite)`.
If I remvoe `noinline` , the call gets inline, then DSE'd correctly.
https://godbolt.org/z/9MEGrYdsa
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