https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121355
Bug ID: 121355
Summary: std::array comparison inside struct comparison does
not inline memcmp
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: tdebock at DRWUK dot com
Target Milestone: ---
On trunk with -O2, memcmps resulting from the std::array equality operator seem
to generally get inlined (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105751
solved by https://gcc.gnu.org/cgit/gcc/commit/?id=d13b86f932ff7b). However,
when using the defaulted equality operator on a struct that contains a
std::array, the memcmp call is still not inlined with -O2 (but is with -O3).
#include <array>
#include <cstdint>
struct A3 {
int64_t x;
std::array<int32_t, 2> a;
bool operator==(const A3&) const = default;
};
bool f(const A3& x, const A3& y) {
return x == y;
}
bool g(const std::array<int32_t, 2>& a, const std::array<int32_t, 2>& b) {
return a == b;
}
with "-std=gnu++20 -O2" gives:
"f(A3 const&, A3 const&)":
mov rcx, QWORD PTR [rsi]
cmp QWORD PTR [rdi], rcx
jne .L6
sub rsp, 8
add rdi, 8
add rsi, 8
mov edx, 8
call "memcmp"
test eax, eax
sete al
add rsp, 8
ret
.L6:
xor eax, eax
ret
"g(std::array<int, 2ul> const&, std::array<int, 2ul> const&)":
mov rax, QWORD PTR [rsi]
cmp QWORD PTR [rdi], rax
sete al
ret
