Specialize sampling routine for immutable sampler data

Treat floating-point sampler values as state that is baked into the
sampling routine, instead of reading it from memory. This offers more
opportunities for optimizing the generated code.

Bug: b/151957215
Change-Id: If41455dece60307a54d97463e9ad26ed052f2588
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/42588
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>

src/Device/Sampler.hpp

diff --git a/src/Device/Sampler.hpp b/src/Device/Sampler.hpp
index a377ea0..3fb3607 100644
--- a/src/Device/Sampler.hpp
+++ b/src/Device/Sampler.hpp
@@ -112,6 +112,11 @@
 	VkSamplerYcbcrModelConversion ycbcrModel;
 	bool studioSwing;    // Narrow range
 	bool swappedChroma;  // Cb/Cr components in reverse order
+
+	float mipLodBias = 0.0f;
+	float maxAnisotropy = 0.0f;
+	float minLod = 0.0f;
+	float maxLod = 0.0f;
 };
 
 }  // namespace sw

src/Pipeline/SamplerCore.cpp

diff --git a/src/Pipeline/SamplerCore.cpp b/src/Pipeline/SamplerCore.cpp
index 811865a..c1031e1 100644
--- a/src/Pipeline/SamplerCore.cpp
+++ b/src/Pipeline/SamplerCore.cpp
@@ -96,7 +96,7 @@
 			computeLod3D(texture, sampler, lod, uuuu, vvvv, wwww, dsx, dsy, function);
 		}
 
-		Float bias = *Pointer<Float>(sampler + OFFSET(vk::Sampler, mipLodBias));
+		Float bias = state.mipLodBias;
 
 		if(function == Bias)
 		{
@@ -110,7 +110,7 @@
 	{
 		// Vulkan 1.1: "The absolute value of mipLodBias must be less than or equal to VkPhysicalDeviceLimits::maxSamplerLodBias"
 		// Hence no explicit clamping to maxSamplerLodBias is required in this case.
-		lod = lodOrBias + *Pointer<Float>(sampler + OFFSET(vk::Sampler, mipLodBias));
+		lod = lodOrBias + state.mipLodBias;
 	}
 	else if(function == Fetch)
 	{
@@ -131,8 +131,8 @@
 			c.y = Float4(lod);  // Unclamped LOD.
 		}
 
-		lod = Max(lod, *Pointer<Float>(sampler + OFFSET(vk::Sampler, minLod)));
-		lod = Min(lod, *Pointer<Float>(sampler + OFFSET(vk::Sampler, maxLod)));
+		lod = Max(lod, state.minLod);
+		lod = Min(lod, state.maxLod);
 
 		if(function == Query)
 		{
@@ -1198,7 +1198,7 @@
 		vDelta = As<Float4>((As<Int4>(dvdx) & mask) | ((As<Int4>(dvdy) & ~mask)));
 
 		anisotropy = lod * Rcp_pp(det);
-		anisotropy = Min(anisotropy, *Pointer<Float>(sampler + OFFSET(vk::Sampler, maxAnisotropy)));
+		anisotropy = Min(anisotropy, state.maxAnisotropy);
 
 		lod *= Rcp_pp(anisotropy * anisotropy);
 	}

src/Pipeline/SpirvShaderSampling.cpp

diff --git a/src/Pipeline/SpirvShaderSampling.cpp b/src/Pipeline/SpirvShaderSampling.cpp
index e2cb5b9..1cd77c3 100644
--- a/src/Pipeline/SpirvShaderSampling.cpp
+++ b/src/Pipeline/SpirvShaderSampling.cpp
@@ -90,6 +90,11 @@
 			samplerState.studioSwing = (sampler->ycbcrConversion->ycbcrRange == VK_SAMPLER_YCBCR_RANGE_ITU_NARROW);
 			samplerState.swappedChroma = (sampler->ycbcrConversion->components.r != VK_COMPONENT_SWIZZLE_R);
 		}
+
+		samplerState.mipLodBias = sampler->mipLodBias;
+		samplerState.maxAnisotropy = sampler->maxAnisotropy;
+		samplerState.minLod = sampler->minLod;
+		samplerState.maxLod = sampler->maxLod;
 	}
 
 	routine = emitSamplerRoutine(instruction, samplerState);