constexpr can't handle vector types

[RKSimon]

Bugzilla Link	42461
Version	unspecified
OS	Windows NT
Blocks	#30794
CC	@erichkeane,@mshockwave,@zygoloid
Fixed by commit(s)	b30c166

Extended Description

Godbolt: https://godbolt.org/z/l-RaB7

We are unable to use __vector_size or ext_vector_type defined types in constexpr functions.

typedef int __v4si __attribute__((__vector_size__(16)));

constexpr int sum_i32(__v4si x) {
  return x[0] + x[1] + x[2] + x[3];
}

constexpr __v4si add_i32(__v4si x, __v4si y) {
  return x + y;
}

clang -g0 -O3

<source>:3:18: error: constexpr function never produces a constant expression [-Winvalid-constexpr]

constexpr __v4si add_i32(__v4si x, __v4si y) {
                 ^

<source>:4:12: note: subexpression not valid in a constant expression
  return x + y;

           ^

<source>:7:15: error: constexpr function never produces a constant expression [-Winvalid-constexpr]

constexpr int sum_i32(__v4si x) {

              ^

<source>:8:10: note: subexpression not valid in a constant expression
  return x[0] + x[1] + x[2] + x[3];

[RKSimon]

CC'ing some more people that might have some ideas on how best to get this done - based off the recent cfe-dev discussions about adding vector ternary support.

[erichkeane]

Partial support here:
https://reviews.llvm.org/D79755

I don't have array subscript expressions implemented (perhaps a future task), so the error in 'sum_i32' still happens but add_i32 will work with that patch.

[yronglin]

IIUC, this issue has already fixed. https://godbolt.org/z/rccbYzYrc

[RKSimon]

IIUC, this issue has already fixed. https://godbolt.org/z/rccbYzYrc

I think this was addressed by #101126 / 7753429