SPIRV-Cross/reference/opt/shaders-msl/vulkan/frag/demote-to-helper.vk.nocompat.msl21.invalid.frag

#include <metal_stdlib>
#include <simd/simd.h>

using namespace metal;

fragment void main0()
{
    bool _9 = simd_is_helper_thread();
    bool helper = _9;
}
Support the SPV_EXT_demote_to_helper_invocation extension. This extension provides a new operation which causes a fragment to be discarded without terminating the fragment shader invocation. The invocation for the discarded fragment becomes a helper invocation, so that derivatives will remain defined. The old `HelperInvocation` builtin becomes undefined when this occurs, so a second new instruction queries the current helper invocation status. This is only fully supported for GLSL. HLSL doesn't support the `IsHelperInvocation` operation and MSL doesn't support the `DemoteToHelperInvocation` op. Fixes #1052. 2019-07-13 20:57:33 +00:00			`#include <metal_stdlib>`
			`#include <simd/simd.h>`

			`using namespace metal;`

			`fragment void main0()`
			`{`
Don't forward uses of an OpIsHelperInvocationEXT op. If this is computed before a `demote`, but used after, forwarding it will produce the wrong value. This does make for uglier shaders, but it's necessary right now to ensure correctness. I needed to use an assembly shader to produce the test for this. `spirv-opt` is not smart enough (or too smart?) to eliminate the variable that would be used in GLSL to express this. 2019-07-18 22:32:35 +00:00			`bool _9 = simd_is_helper_thread();`
Update for pull request #1162 rev. 1 2019-09-24 22:13:04 +00:00			`bool helper = _9;`
Support the SPV_EXT_demote_to_helper_invocation extension. This extension provides a new operation which causes a fragment to be discarded without terminating the fragment shader invocation. The invocation for the discarded fragment becomes a helper invocation, so that derivatives will remain defined. The old `HelperInvocation` builtin becomes undefined when this occurs, so a second new instruction queries the current helper invocation status. This is only fully supported for GLSL. HLSL doesn't support the `IsHelperInvocation` operation and MSL doesn't support the `DemoteToHelperInvocation` op. Fixes #1052. 2019-07-13 20:57:33 +00:00			`}`