Argument promotion not happening for static function.

[Quuxplusone]

Bugzilla Link	PR52554
Status	NEW
Importance	P enhancement
Reported by	Jeff Muizelaar (jmuizelaar@mozilla.com)
Reported on	2021-11-18 18:35:42 -0800
Last modified on	2021-11-18 18:35:42 -0800
Version	trunk
Hardware	PC All
CC	llvm-bugs@lists.llvm.org
Fixed by commit(s)
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Given:

__attribute__((noinline))
static int foo(const int &x) {
    return x;
}

int r(int x) {
    return foo(x);
}

GCC gives:

foo(int const&) [clone .isra.0]:
        mov     eax, edi
        ret
r(int):
        jmp     foo(int const&) [clone .isra.0]

vs clang's:

r(int):                                  # @r(int)
        push    rax
        mov     dword ptr [rsp + 4], edi
        lea     rdi, [rsp + 4]
        call    foo(int const&)
        pop     rcx
        ret
foo(int const&):                             # @foo(int const&)
        mov     eax, dword ptr [rdi]
        ret