SPIRV-Cross/reference/shaders-msl/asm/comp/atomic-decrement.asm.comp
Chip Davis 058f1a0933 MSL: Handle coherent, volatile, and restrict.
This maps them to their MSL equivalents. I've mapped `Coherent` to
`volatile` since MSL doesn't have anything weaker than `volatile` but
stronger than nothing.

As part of this, I had to remove the implicit `volatile` added for
atomic operation casts. If the buffer is already `coherent` or
`volatile`, then we would add a second `volatile`, which would be
redundant. I think this is OK even when the buffer *doesn't* have
`coherent`: `T *` is implicitly convertible to `volatile T *`, but not
vice-versa. It seems to compile OK at any rate. (Note that the
non-`volatile` overloads of the atomic functions documented in the spec
aren't present in the MSL 2.2 stdlib headers.)

`restrict` is tricky, because in MSL, as in C++, it needs to go *after*
the asterisk or ampersand for the pointer type it's modifying.

Another issue is that, in the `Simple`, `GLSL450`, and `Vulkan` memory
models, `Restrict` is the default (i.e. does not need to be specified);
but MSL likely follows the `OpenCL` model where `Aliased` is the
default. We probably need to implicitly set either `Restrict` or
`Aliased` depending on the module's declared memory model.
2019-07-11 10:22:30 -05:00

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#pragma clang diagnostic ignored "-Wmissing-prototypes"
#pragma clang diagnostic ignored "-Wunused-variable"
#include <metal_stdlib>
#include <simd/simd.h>
#include <metal_atomic>
using namespace metal;
struct u0_counters
{
uint c;
};
// Returns 2D texture coords corresponding to 1D texel buffer coords
uint2 spvTexelBufferCoord(uint tc)
{
return uint2(tc % 4096, tc / 4096);
}
kernel void main0(device u0_counters& u0_counter [[buffer(0)]], texture2d<uint, access::write> u0 [[texture(0)]], uint3 gl_GlobalInvocationID [[thread_position_in_grid]])
{
uint _29 = atomic_fetch_sub_explicit((device atomic_uint*)&u0_counter.c, 1, memory_order_relaxed);
float4 r0;
r0.x = as_type<float>(_29);
u0.write(uint4(uint(int(gl_GlobalInvocationID.x))), spvTexelBufferCoord(((uint(as_type<int>(r0.x)) * 1u) + (uint(0) >> 2u))));
}