| Issue |
89820
|
| Summary |
Suboptimal codegen for comparison of trivially equality comparable types
|
| Labels |
|
| Assignees |
|
| Reporter |
AMP999
|
Right now `eqcompare_T` has good codegen but `eqcompare_U` and `eqcompare_O` have worse codegen. Ideally, they'd all have the same codegen, since the comparison semantics for each of them are identical.
https://godbolt.org/z/GYdGc6xqa
```
#include <compare>
struct T {
int i;
int j;
friend auto operator<=>(const T&, const T&) = default;
};
static_assert(__is_trivially_equality_comparable(T));
struct U {
int i;
short a, b;
friend auto operator<=>(const U&, const U&) = default;
};
static_assert(__is_trivially_equality_comparable(U));
struct ObjRep {
alignas(T) char data[sizeof(T)];
friend auto operator<=>(const ObjRep&, const ObjRep&) = default;
};
static_assert(__is_trivially_equality_comparable(ObjRep));
// Since all three are trivially equality-comparable, these should have the same codegen.
// Clang fails to optimize.
bool eqcompare_T(T *a, T *b) { return *a == *b; }
bool eqcompare_U(U *a, U *b) { return *a == *b; }
bool eqcompare_O(ObjRep *a, ObjRep *b) { return *a == *b; }
```
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