Fix lod plumbing for Fetch

src/Pipeline/SamplerCore.cpp

@@ -121,7 +121,7 @@ namespace sw
 		}
 		else UNREACHABLE("Sampler function %d", int(function));
 
-		if(function != Base)
+		if(function != Base && function != Fetch)
 		{
 			lod += *Pointer<Float>(sampler + OFFSET(vk::Sampler, mipLodBias));
 			lod = Max(lod, *Pointer<Float>(sampler + OFFSET(vk::Sampler, minLod)));

src/Pipeline/SpirvShader.cpp

@@ -4806,6 +4806,14 @@ namespace sw
 				in[i] = dyValue.Float(j);
 			}
 		}
+		else if (instruction.samplerMethod == Fetch)
+		{
+			// The instruction didn't provide a lod operand, but the sampler's Fetch
+			// function requires one to be present. If no lod is supplied, the default
+			// is zero.
+			in[i] = As<SIMD::Float>(SIMD::Int(0));
+			i++;
+		}
 
 		if(constOffset)
 		{

src/Pipeline/SpirvShader.hpp

@@ -527,7 +527,7 @@ namespace sw
 					// Parameters are passed to the sampling routine in this order:
 					uint32_t coordinates : 3;       // 1-4 (does not contain projection component)
 				//	uint32_t dref : 1;              // Indicated by Variant::ProjDref|Dref
-				//	uint32_t lodOrBias : 1;         // Indicated by SamplerMethod::Lod|Bias
+				//	uint32_t lodOrBias : 1;         // Indicated by SamplerMethod::Lod|Bias|Fetch
 					uint32_t gradComponents : 2;    // 0-3 (for each of dx / dy)
 					uint32_t offsetComponents : 2;  // 0-3
 				};

src/Pipeline/SpirvShaderSampling.cpp

@@ -123,7 +123,7 @@ SpirvShader::ImageSampler *SpirvShader::emitSamplerFunction(ImageInstruction ins
 			uvw[2] = in[1];  // Move 1D layer coordinate to 2D layer coordinate index.
 		}
 
-		if(instruction.samplerMethod == Lod || instruction.samplerMethod == Bias)
+		if(instruction.samplerMethod == Lod || instruction.samplerMethod == Bias || instruction.samplerMethod == Fetch)
 		{
 			lodOrBias = in[i];
 			i++;