| Issue |
164150
|
| Summary |
constexpr structured bindings bad codegen P2686
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
ordinary-github-user
|
`-std=c++26 -O3 -Wall -march=znver5 -fno-exceptions -fconstexpr-steps=4294967295 -fbracket-depth=4294967295`
```c
#include <array>
#include <cstdint>
using u8 = std::uint8_t;
template<u8 N>
struct Range
{
template<std::size_t I>
constexpr friend u8 get(Range) noexcept { return I; }
};
namespace std
{
template<u8 N>
struct tuple_size<Range<N>> {static constexpr std::size_t value = N;};
template<std::size_t I, u8 N>
struct tuple_element<I, Range<N>> {using type = u8;};
}
template<u8 x>constexpr u8 constant{x};
template<std::size_t L, std::size_t R>
__attribute__((always_inline)) inline constexpr std::array<u8, L+R> concat(const std::array<u8, L>& l, const std::array<u8, R>& r)
{
static constexpr auto [...I] = Range<L>{};
static constexpr auto [...J] = Range<R>{};
#if 0
return { l[I]..., r[J]... };//bad codegen
#else
return { l[constant<I>]..., r[constant<J>]... };//good codegen
#endif
}
auto test(const std::array<u8, 16>& l, const std::array<u8, 16>& r)
{
return concat(l, r);
}
```
good codegen
```
test(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&):
vmovups xmm0, xmmword ptr [rsi]
vmovups xmm1, xmmword ptr [rdx]
mov rax, rdi
vmovups xmmword ptr [rdi + 16], xmm1
vmovups xmmword ptr [rdi], xmm0
ret
```
bad codegen
```
test(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&):
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I]
mov rax, rdi
movzx ecx, byte ptr [rsi + rcx]
mov byte ptr [rdi], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.2)]
movzx ecx, byte ptr [rsi + rcx]
mov byte ptr [rdi + 1], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.4)]
movzx ecx, byte ptr [rsi + rcx]
mov byte ptr [rdi + 2], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.6)]
movzx ecx, byte ptr [rsi + rcx]
mov byte ptr [rdi + 3], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.8)]
movzx ecx, byte ptr [rsi + rcx]
mov byte ptr [rdi + 4], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.10)]
movzx ecx, byte ptr [rsi + rcx]
mov byte ptr [rdi + 5], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.12)]
movzx ecx, byte ptr [rsi + rcx]
mov byte ptr [rdi + 6], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.14)]
movzx ecx, byte ptr [rsi + rcx]
mov byte ptr [rdi + 7], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.16)]
movzx ecx, byte ptr [rsi + rcx]
mov byte ptr [rdi + 8], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.18)]
movzx ecx, byte ptr [rsi + rcx]
mov byte ptr [rdi + 9], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.20)]
movzx ecx, byte ptr [rsi + rcx]
mov byte ptr [rdi + 10], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.22)]
movzx ecx, byte ptr [rsi + rcx]
mov byte ptr [rdi + 11], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.24)]
movzx ecx, byte ptr [rsi + rcx]
mov byte ptr [rdi + 12], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.26)]
movzx ecx, byte ptr [rsi + rcx]
mov byte ptr [rdi + 13], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.28)]
movzx ecx, byte ptr [rsi + rcx]
mov byte ptr [rdi + 14], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.30)]
movzx ecx, byte ptr [rsi + rcx]
mov byte ptr [rdi + 15], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J]
movzx ecx, byte ptr [rdx + rcx]
mov byte ptr [rdi + 16], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.32)]
movzx ecx, byte ptr [rdx + rcx]
mov byte ptr [rdi + 17], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.34)]
movzx ecx, byte ptr [rdx + rcx]
mov byte ptr [rdi + 18], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.36)]
movzx ecx, byte ptr [rdx + rcx]
mov byte ptr [rdi + 19], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.38)]
movzx ecx, byte ptr [rdx + rcx]
mov byte ptr [rdi + 20], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.40)]
movzx ecx, byte ptr [rdx + rcx]
mov byte ptr [rdi + 21], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.42)]
movzx ecx, byte ptr [rdx + rcx]
mov byte ptr [rdi + 22], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.44)]
movzx ecx, byte ptr [rdx + rcx]
mov byte ptr [rdi + 23], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.46)]
movzx ecx, byte ptr [rdx + rcx]
mov byte ptr [rdi + 24], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.48)]
movzx ecx, byte ptr [rdx + rcx]
mov byte ptr [rdi + 25], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.50)]
movzx ecx, byte ptr [rdx + rcx]
mov byte ptr [rdi + 26], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.52)]
movzx ecx, byte ptr [rdx + rcx]
mov byte ptr [rdi + 27], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.54)]
movzx ecx, byte ptr [rdx + rcx]
mov byte ptr [rdi + 28], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.56)]
movzx ecx, byte ptr [rdx + rcx]
mov byte ptr [rdi + 29], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.58)]
movzx ecx, byte ptr [rdx + rcx]
mov byte ptr [rdi + 30], cl
movzx ecx, byte ptr [rip + reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.60)]
movzx ecx, byte ptr [rdx + rcx]
mov byte ptr [rdi + 31], cl
ret
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I:
.byte 0
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.2):
.byte 1
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.4):
.byte 2
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.6):
.byte 3
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.8):
.byte 4
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.10):
.byte 5
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.12):
.byte 6
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.14):
.byte 7
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.16):
.byte 8
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.18):
.byte 9
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.20):
.byte 10
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.22):
.byte 11
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.24):
.byte 12
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.26):
.byte 13
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.28):
.byte 14
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::I (.30):
.byte 15
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J:
.byte 0
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.32):
.byte 1
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.34):
.byte 2
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.36):
.byte 3
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.38):
.byte 4
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.40):
.byte 5
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.42):
.byte 6
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.44):
.byte 7
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.46):
.byte 8
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.48):
.byte 9
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.50):
.byte 10
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.52):
.byte 11
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.54):
.byte 12
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.56):
.byte 13
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.58):
.byte 14
reference temporary for std::array<unsigned char, 16ul + 16ul> concat<16ul, 16ul>(std::array<unsigned char, 16ul> const&, std::array<unsigned char, 16ul> const&)::J (.60):
.byte 15
```
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