SPIRV-Cross/reference/opt/shaders-msl/frag/complex-expression-in-access-chain.frag

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

using namespace metal;

struct UBO
{
    float4 results[1024];
};

struct main0_out
{
    float4 FragColor [[color(0)]];
};

struct main0_in
{
    int vIn [[user(locn0)]];
    int vIn2 [[user(locn1)]];
};

fragment main0_out main0(main0_in in [[stage_in]], device UBO& _34 [[buffer(0)]], texture2d<int> Buf [[texture(0)]], sampler BufSmplr [[sampler(0)]], float4 gl_FragCoord [[position]])
{
    main0_out out = {};
    int _40 = Buf.read(uint2(int2(gl_FragCoord.xy)), 0).x % 16;
    out.FragColor = (_34.results[_40] + _34.results[_40]) + _34.results[(in.vIn * in.vIn) + (in.vIn2 * in.vIn2)];
    return out;
}
Register implied expression reads in OpLoad/OpAccessChain. This is required to avoid relying on complex sub-expression elimination in compilers, and generates cleaner code. The problem case is if a complex expression is used in an access chain, like: Composite comp = buffer[texture(...)]; vec4 a = comp.a + comp.b + comp.c; Before, we did not have common subexpression tracking for OpLoad/OpAccessChain, so we easily ended up with code like: vec4 a = buffer[texture(...)].a + buffer[texture(...)].b + buffer[texture(...)].c; A good compiler will optimize this, but we should not rely on it, and forcing texture(...) to a temporary also looks better. The solution is to add a vector "implied_expression_reads", which works similarly to expression_dependencies. We also need an extra mechanism in to_expression which lets us skip expression read checking and do it later. E.g. for expr -> access chain -> load, we should only trigger a read of expr when using the loaded expression. 2019-01-04 12:19:50 +00:00			`#include <metal_stdlib>`
			`#include <simd/simd.h>`

			`using namespace metal;`

			`struct UBO`
			`{`
			`float4 results[1024];`
			`};`

			`struct main0_out`
			`{`
			`float4 FragColor [[color(0)]];`
			`};`

			`struct main0_in`
			`{`
			`int vIn [[user(locn0)]];`
			`int vIn2 [[user(locn1)]];`
			`};`

MSL: Rewrite how resource indices are fallback-assigned. We used to use the Binding decoration for this, but this method is hopelessly broken. If no explicit MSL resource remapping exists, we remap automatically in a manner which should always "just work". 2019-06-21 10:44:33 +00:00			`fragment main0_out main0(main0_in in [[stage_in]], device UBO& _34 [[buffer(0)]], texture2d<int> Buf [[texture(0)]], sampler BufSmplr [[sampler(0)]], float4 gl_FragCoord [[position]])`
Register implied expression reads in OpLoad/OpAccessChain. This is required to avoid relying on complex sub-expression elimination in compilers, and generates cleaner code. The problem case is if a complex expression is used in an access chain, like: Composite comp = buffer[texture(...)]; vec4 a = comp.a + comp.b + comp.c; Before, we did not have common subexpression tracking for OpLoad/OpAccessChain, so we easily ended up with code like: vec4 a = buffer[texture(...)].a + buffer[texture(...)].b + buffer[texture(...)].c; A good compiler will optimize this, but we should not rely on it, and forcing texture(...) to a temporary also looks better. The solution is to add a vector "implied_expression_reads", which works similarly to expression_dependencies. We also need an extra mechanism in to_expression which lets us skip expression read checking and do it later. E.g. for expr -> access chain -> load, we should only trigger a read of expr when using the loaded expression. 2019-01-04 12:19:50 +00:00			`{`
			`main0_out out = {};`
			`int _40 = Buf.read(uint2(int2(gl_FragCoord.xy)), 0).x % 16;`
			`out.FragColor = (_34.results[_40] + _34.results[_40]) + _34.results[(in.vIn * in.vIn) + (in.vIn2 * in.vIn2)];`
			`return out;`
			`}`