https://bugs.llvm.org/show_bug.cgi?id=52269
Bug ID: 52269
Summary: Passing small struct by value - suboptimal codegen
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
Assignee: unassignedb...@nondot.org
Reporter: david.bolvan...@gmail.com
CC: craig.top...@gmail.com, llvm-bugs@lists.llvm.org,
llvm-...@redking.me.uk, pengfei.w...@intel.com,
spatel+l...@rotateright.com
struct X
{
char mem0[32];
char mem1[32];
};
void bar (struct X);
void
foo1(struct X *x)
{
bar(*x);
}
LLVM -O3 or even -Oz:
foo1: # @foo1
sub rsp, 136
movups xmm0, xmmword ptr [rdi]
movups xmm1, xmmword ptr [rdi + 16]
movups xmm2, xmmword ptr [rdi + 32]
movups xmm3, xmmword ptr [rdi + 48]
movaps xmmword ptr [rsp + 112], xmm3
movaps xmmword ptr [rsp + 96], xmm2
movaps xmmword ptr [rsp + 80], xmm1
movaps xmmword ptr [rsp + 64], xmm0
movaps xmm0, xmmword ptr [rsp + 64]
movaps xmm1, xmmword ptr [rsp + 80]
movaps xmm2, xmmword ptr [rsp + 96]
movaps xmm3, xmmword ptr [rsp + 112]
movups xmmword ptr [rsp + 48], xmm3
movups xmmword ptr [rsp + 32], xmm2
movups xmmword ptr [rsp + 16], xmm1
movups xmmword ptr [rsp], xmm0
call bar
add rsp, 136
ret
GCC:
foo1:
sub rsp, 72
movdqu xmm0, XMMWORD PTR [rdi]
movdqu xmm1, XMMWORD PTR [rdi+16]
movdqu xmm2, XMMWORD PTR [rdi+32]
movdqu xmm3, XMMWORD PTR [rdi+48]
movups XMMWORD PTR [rsp], xmm0
movups XMMWORD PTR [rsp+16], xmm1
movups XMMWORD PTR [rsp+32], xmm2
movups XMMWORD PTR [rsp+48], xmm3
call bar
add rsp, 72
ret
--
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