https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103648
Bug ID: 103648
Summary: Missed optimization on arm64 when returning an empty
struct.
Product: gcc
Version: 11.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: boleyn.su at gmail dot com
Target Milestone: ---
In the following C code, gcc generates different assembly for `f` and `g`
```c
struct Void {};
struct Void f(int x) {
return (struct Void) {};
}
void g(int x) {}
```
I believe it can be optimized somehow and clang does optimize them to be
identical.
gcc trunk vs clang trunk on ARM 64-bit https://godbolt.org/z/W8ocj6vsK
Jonathan Wakely finds something that may be related.
https://reviews.llvm.org/D89490 which references
https://developer.apple.com/documentation/xcode/writing-arm64-code-for-apple-platforms#Pass-Arguments-to-Functions-Correctly
