Ben Clayton f47887d207 tint/writer/msl: Generate an array<T,N> helper
And remove the WrapArraysInStructs transform.

Wrapping arrays in structures becomes troublesome for `const` arrays, as
currently WGSL does not allow `const` structures.

MSL 2.0+ has a builtin array<> helper, but we're targetting MSL 1.2, so
we have to emit our own. Fortunately, it can be done with a few lines of
templated code.

This produces significantly cleaner output.

Change-Id: Ifc92ef21e09befa252a07c856c4b5afdc51cc2e4
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/94540
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@chromium.org>
Reviewed-by: David Neto <dneto@google.com>
2022-06-24 17:01:59 +00:00

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#include <metal_stdlib>
using namespace metal;
template<typename T, size_t N>
struct tint_array {
const constant T& operator[](size_t i) const constant { return elements[i]; }
device T& operator[](size_t i) device { return elements[i]; }
const device T& operator[](size_t i) const device { return elements[i]; }
thread T& operator[](size_t i) thread { return elements[i]; }
const thread T& operator[](size_t i) const thread { return elements[i]; }
threadgroup T& operator[](size_t i) threadgroup { return elements[i]; }
const threadgroup T& operator[](size_t i) const threadgroup { return elements[i]; }
T elements[N];
};
struct S {
/* 0x0000 */ packed_uint3 v;
/* 0x000c */ tint_array<int8_t, 4> tint_pad;
};
void f(device S* const tint_symbol) {
(*(tint_symbol)).v = uint3(1u, 2u, 3u);
(*(tint_symbol)).v[0] = 1u;
(*(tint_symbol)).v[1] = 2u;
(*(tint_symbol)).v[2] = 3u;
}