[SPIR-V][vk::SampledTexture] #2. Add .CalculateLevelOfDetailUnclamped() and .Gather() methods for vk::SampledTexture2D type. (microsoft#8070)

Part of microsoft#7979

Implement methods for `vk::SampledTexture2D`:
```hlsl
float CalculateLevelOfDetailUnclamped(float2 location);
<Template Type>4 Gather(float2 location, [int2 offset], [uint status]);
```

Author: luciechoi

tools/clang/include/clang/SPIRV/SpirvBuilder.h

@@ -339,6 +339,10 @@ class SpirvBuilder {
 
   /// \brief Creates SPIR-V instructions for gathering the given image.
   ///
+  /// If the of `image` is a sampled image, then that image will be gathered.
+  /// In this case, `sampler` must be `nullptr`. If `image` is not a sampled
+  /// image, a sampled image will be created by combining `image` and `sampler`.
+  ///
   /// If compareVal is given a non-null value, OpImageDrefGather or
   /// OpImageSparseDrefGather will be generated; otherwise, OpImageGather or
   /// OpImageSparseGather will be generated.

tools/clang/lib/SPIRV/SpirvBuilder.cpp

@@ -714,8 +714,15 @@ SpirvInstruction *SpirvBuilder::createImageGather(
   assert(insertPoint && "null insert point");
 
   // An OpSampledImage is required to do the image sampling.
-  auto *sampledImage =
-      createSampledImage(imageType, image, sampler, loc, range);
+  // Skip creating OpSampledImage if the imageType is a sampled texture.
+  SpirvInstruction *sampledImage = nullptr;
+  if (isSampledTexture(imageType)) {
+    assert(!sampler &&
+           "sampler must be null when sampling from a sampled texture");
+    sampledImage = image;
+  } else {
+    sampledImage = createSampledImage(imageType, image, sampler, loc, range);
+  }
 
   // TODO: Update ImageGather to accept minLod if necessary.
   const auto mask = composeImageOperandsMask(

tools/clang/test/CodeGenSPIRV/vk.sampledtexture.calculate-lod-unclamped.hlsl

@@ -0,0 +1,21 @@
+// RUN: %dxc -T ps_6_8 -E main -fcgl  %s -spirv | FileCheck %s
+
+// CHECK: OpCapability ImageQuery
+
+vk::SampledTexture2D<float4> t1 : register(t0);
+
+// CHECK: %type_2d_image = OpTypeImage %float 2D 0 0 0 1 Unknown
+// CHECK: %type_sampled_image = OpTypeSampledImage %type_2d_image
+// CHECK: [[ptr:%[a-zA-Z0-9_]+]] = OpTypePointer UniformConstant %type_sampled_image
+
+// CHECK: %t1 = OpVariable [[ptr]] UniformConstant
+
+void main() {
+  float2 xy = float2(0.5, 0.5);
+
+//CHECK:          [[tex1:%[a-zA-Z0-9_]+]] = OpLoad %type_sampled_image %t1
+//CHECK-NEXT:    [[xy_load:%[a-zA-Z0-9_]+]] = OpLoad %v2float %xy
+//CHECK-NEXT: [[query:%[a-zA-Z0-9_]+]] = OpImageQueryLod %v2float [[tex1]] [[xy_load]]
+//CHECK-NEXT:        {{%[0-9]+}} = OpCompositeExtract %float [[query]] 1
+  float lod1 = t1.CalculateLevelOfDetailUnclamped(xy);
+}

tools/clang/test/CodeGenSPIRV/vk.sampledtexture.gather.hlsl

@@ -0,0 +1,42 @@
+// RUN: %dxc -T ps_6_7 -E main -fcgl  %s -spirv | FileCheck %s
+
+// CHECK: OpCapability SparseResidency
+
+// CHECK: [[v2fc:%[0-9]+]] = OpConstantComposite %v2float %float_0_5 %float_0_25
+// CHECK: [[v2ic:%[0-9]+]] = OpConstantComposite %v2int %int_2 %int_3
+
+// CHECK: [[type_2d_image_1:%[a-zA-Z0-9_]+]] = OpTypeImage %float 2D 0 0 0 1 Unknown
+// CHECK: [[type_sampled_image_1:%[a-zA-Z0-9_]+]] = OpTypeSampledImage [[type_2d_image_1]]
+// CHECK: [[ptr_type_1:%[a-zA-Z0-9_]+]] = OpTypePointer UniformConstant [[type_sampled_image_1]]
+
+// CHECK: [[type_2d_image_2:%[a-zA-Z0-9_]+]] = OpTypeImage %uint 2D 0 0 0 1 Unknown
+// CHECK: [[type_sampled_image_2:%[a-zA-Z0-9_]+]] = OpTypeSampledImage [[type_2d_image_2]]
+// CHECK: [[ptr_type_2:%[a-zA-Z0-9_]+]] = OpTypePointer UniformConstant [[type_sampled_image_2]]
+
+// CHECK: %SparseResidencyStruct = OpTypeStruct %uint %v4float
+
+// CHECK: [[tex1:%[a-zA-Z0-9_]+]] = OpVariable [[ptr_type_1]] UniformConstant
+// CHECK: [[tex2:%[a-zA-Z0-9_]+]] = OpVariable [[ptr_type_2]] UniformConstant
+
+vk::SampledTexture2D<float4> tex1 : register(t1);
+vk::SampledTexture2D<uint> tex2 : register(t2);
+
+float4 main() : SV_Target {
+
+// CHECK: [[tex1_load:%[a-zA-Z0-9_]+]] = OpLoad [[type_sampled_image_1]] [[tex1]]
+// CHECK:      [[val1:%[a-zA-Z0-9_]+]] = OpImageGather %v4float [[tex1_load]] [[v2fc]] %int_0 None
+    float4 val1 = tex1.Gather(float2(0.5, 0.25));
+
+// CHECK: [[tex2_load:%[a-zA-Z0-9_]+]] = OpLoad [[type_sampled_image_2]] [[tex2]]
+// CHECK:      [[val2:%[a-zA-Z0-9_]+]] = OpImageGather %v4uint [[tex2_load]] [[v2fc]] %int_0 ConstOffset [[v2ic]]
+    uint4 val2 = tex2.Gather(float2(0.5, 0.25), int2(2, 3));
+
+// CHECK: [[tex3_load:%[a-zA-Z0-9_]+]] = OpLoad [[type_sampled_image_1]] [[tex1]]
+// CHECK:      [[val3:%[a-zA-Z0-9_]+]] = OpImageSparseGather %SparseResidencyStruct [[tex3_load]] [[v2fc]] %int_0 ConstOffset [[v2ic]]
+// CHECK:  [[status_0:%[a-zA-Z0-9_]+]] = OpCompositeExtract %uint [[val3]] 0
+// CHECK:                                OpStore %status [[status_0]]
+    uint status;
+    float4 val3 = tex1.Gather(float2(0.5, 0.25), int2(2, 3), status);
+
+    return 1.0;
+}

utils/hct/gen_intrin_main.txt

@@ -1239,4 +1239,8 @@ namespace VkSampledTexture2DMethods {
     $classT [[ro]] Sample(in float<2> x, in int<2> o, in float clamp) : tex2d_t_o_cl;
     $classT [[]] Sample(in float<2> x, in int<2> o, in float clamp, out uint_only status) : tex2d_t_o_cl_s;
     float [[ro]] CalculateLevelOfDetail(in float<2> x) : tex2d_t_calc_lod;
+    float [[ro]] CalculateLevelOfDetailUnclamped(in float<2> x) : tex2d_t_calc_lod_unclamped;
+    $match<0, -1> void<4> [[ro]] Gather(in float<2> x) : tex2d_t_gather;
+    $match<0, -1> void<4> [[ro]] Gather(in float<2> x, in int<2> o) : tex2d_t_gather_o;
+    $match<0, -1> void<4> [[]] Gather(in float<2> x, in int<2> o, out uint_only status) : tex2d_t_gather_o_s;
 } namespace