e2d7cd685d
This patch makes the dead_on_return parameter attribute optionally require a number
of bytes to be passed in to specify the number of bytes known to be dead
upon function return/unwind. This is aimed at enabling annotating the
this pointer in C++ destructors with dead_on_return in clang. We need
this to handle cases like the following:
```
struct X {
int n;
~X() {
this[n].n = 0;
}
};
void f() {
X xs[] = {42, -1};
}
```
Where we only certain that sizeof(X) bytes are dead upon return of ~X.
Otherwise DSE would be able to eliminate the store in ~X which would not
be correct.
This patch only does the wiring within IR. Future patches will make
clang emit correct sizing information and update DSE to only delete
stores to objects marked dead_on_return that are provably in bounds of
the number of bytes specified to be dead_on_return.
Reviewers: nikic, alinas, antoniofrighetto
Pull Request: https://github.com/llvm/llvm-project/pull/171712
21 lines
459 B
C++
21 lines
459 B
C++
// RUN: %clang_cc1 %s -triple=arm-unknown-linux-gnueabi -target-abi aapcs -emit-llvm -o - | FileCheck %s
|
|
|
|
class SMLoc {
|
|
const char *Ptr;
|
|
public:
|
|
SMLoc();
|
|
SMLoc(const SMLoc &RHS);
|
|
};
|
|
SMLoc foo(void *p);
|
|
void bar(void *x) {
|
|
foo(x);
|
|
}
|
|
void zed(SMLoc x);
|
|
void baz() {
|
|
SMLoc a;
|
|
zed(a);
|
|
}
|
|
|
|
// CHECK: declare void @_Z3fooPv(ptr dead_on_unwind writable sret(%class.SMLoc) align 4, ptr noundef)
|
|
// CHECK: declare void @_Z3zed5SMLoc(ptr noundef dead_on_return)
|