shader: apply the LOD clamp of image_sample _cl variants

Co-authored-by: Senaxx <michelbeld@gmail.com>

src/graphics/presentation/window/vulkanWindow.cpp

@@ -337,6 +337,7 @@ static void VulkanFindPhysicalDevice(vk::Instance instance, vk::SurfaceKHR surfa
 
 		check_feature(device_features2.features.shaderImageGatherExtended,
 		              "shaderImageGatherExtended");
+		check_feature(device_features2.features.shaderResourceMinLod, "shaderResourceMinLod");
 
 		check_feature(device_features2.features.independentBlend, "independentBlend");
 		check_feature(device_features2.features.tessellationShader, "tessellationShader");
@@ -636,6 +637,7 @@ static vk::Device VulkanCreateDevice(GraphicContext& graphics,
 	device_features.shaderStorageImageMultisample        =
 	    supported_features2.features.shaderStorageImageMultisample;
 	device_features.shaderImageGatherExtended            = VK_TRUE;
+	device_features.shaderResourceMinLod                 = VK_TRUE;
 	device_features.independentBlend                     = VK_TRUE;
 	device_features.dualSrcBlend                         = VK_TRUE;
 	device_features.tessellationShader                   = VK_TRUE;

src/graphics/shader/recompiler/backend/spirv/spirvEmitterImage.cpp

@@ -77,6 +77,7 @@ ImageSampleLayout Layout(const IR::MemoryInfo& mem) {
 	layout.coord = cursor;
 	cursor += info.coordinate_components;
 	if (HasFlag(mem, Decoder::ImageSampleFlagLod)) layout.lod = cursor++;
+	if (HasFlag(mem, Decoder::ImageSampleFlagLodClamp)) layout.clamp = cursor++;
 	return layout;
 }
 
@@ -1069,7 +1070,12 @@ void EmitImage(ValueEmitContext& ctx, const IR::Inst& inst) {
 				dref_value = AddressF32(ctx, mem, *address, layout.dref);
 			}
 		}
-		std::array<uint32_t, 4> operands {};
+		// _cl clamps the computed LOD from below.
+		uint32_t min_lod = 0;
+		if (layout.clamp != NoImageComponent) {
+			min_lod = AddressF32(ctx, mem, *address, layout.clamp);
+		}
+		std::array<uint32_t, 5> operands {};
 		size_t operand_count = 0;
 		if (HasFlag(mem, Decoder::ImageSampleFlagDerivative)) {
 			operands[0] = spv::ImageOperandsGradMask;
@@ -1081,6 +1087,11 @@ void EmitImage(ValueEmitContext& ctx, const IR::Inst& inst) {
 			if (HasFlag(mem, Decoder::ImageSampleFlagLod) && layout.lod != NoImageComponent) {
 				lod = AddressF32(ctx, mem, *address, layout.lod);
 			}
+			// SPIR-V takes MinLod only with implicit LOD or Grad.
+			if (min_lod != 0) {
+				lod     = EmitGlsl<GLSLstd450FMax, IR::Type::F32>(state, lod, min_lod);
+				min_lod = 0;
+			}
 			operands[0] = spv::ImageOperandsLodMask;
 			operands[1] = lod;
 			operand_count = 2;
@@ -1104,6 +1115,13 @@ void EmitImage(ValueEmitContext& ctx, const IR::Inst& inst) {
 				sample_operands[sample_operand_count++] = PackedOffset(
 				    ctx, offset_value, candidate.dimension, sample_operands[0]);
 			}
+			// MinLod follows the offset in operand order.
+			if (min_lod != 0) {
+				state.builder.RequireCapability(spv::CapabilityMinLod);
+				sample_operand_count = std::max(size_t{1}, sample_operand_count);
+				sample_operands[0] |= spv::ImageOperandsMinLodMask;
+				sample_operands[sample_operand_count++] = min_lod;
+			}
 			const auto coord =
 			    CoordF32(ctx, mem, *address, layout.coord,
 			             ImageDimensionInfoFor(candidate.dimension).coordinate_components,

src/graphics/shader/recompiler/backend/spirv/spirvEmitterInternal.h

@@ -283,6 +283,7 @@ struct ImageSampleLayout {
 	uint32_t bias   = NoImageComponent;
 	uint32_t coord  = 0;
 	uint32_t lod    = NoImageComponent;
+	uint32_t clamp  = NoImageComponent;
 	uint32_t grad_x = NoImageComponent;
 	uint32_t grad_y = NoImageComponent;
 };

src/graphics/shader/recompiler/frontend/decode/ImageOps.cpp

@@ -73,7 +73,7 @@ constexpr uint32_t ImageSampleAddressComponents(uint32_t flags, ImageDimension d
 	if ((flags & ImageSampleFlagBias) != 0) {
 		components++;
 	}
-	if ((flags & ImageSampleFlagLod) != 0) {
+	if ((flags & (ImageSampleFlagLod | ImageSampleFlagLodClamp)) != 0) {
 		components++;
 	}
 	if ((flags & ImageSampleFlagDerivative) != 0) {