Add spirv-opt convert-to-sampled-image pass (#4340)

convert-to-sampled-image pass converts images and/or samplers with
given pairs of descriptor set and binding to sampled image.

If a pair of an image and a sampler have the same pair of descriptor
set and binding that is one of the given pairs, they will be
converted to a sampled image. In addition, if only an image has the
descriptor set and binding that is one of the given pairs, it will
be converted to a sampled image as well.

For example, when we have

  %a = OpLoad %type_2d_image %texture
  %b = OpLoad %type_sampler %sampler
  %combined = OpSampledImage %type_sampled_image %a %b
  %value = OpImageSampleExplicitLod %v4float %combined ...

1. If %texture and %sampler have the same descriptor set and binding

  %combine_texture_and_sampler = OpVaraible %ptr_type_sampled_image_Uniform
  ...
  %combined = OpLoad %type_sampled_image %combine_texture_and_sampler
  %value = OpImageSampleExplicitLod %v4float %combined ...

2. If %texture and %sampler have different pairs of descriptor set and binding

  %a = OpLoad %type_sampled_image %texture
  %extracted_image = OpImage %type_2d_image %a
  %b = OpLoad %type_sampler %sampler
  %combined = OpSampledImage %type_sampled_image %extracted_image %b
  %value = OpImageSampleExplicitLod %v4float %combined ...

1 files changed, 2 insertions, 0 deletions

diff --git a/BUILD.gn b/BUILD.gn
index 036a0a1c0..8a0e5014d 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -608,6 +608,8 @@ static_library("spvtools_opt") {
     "source/opt/constants.h",
     "source/opt/control_dependence.cpp",
     "source/opt/control_dependence.h",
+    "source/opt/convert_to_sampled_image_pass.cpp",
+    "source/opt/convert_to_sampled_image_pass.h",
     "source/opt/convert_to_half_pass.cpp",
     "source/opt/convert_to_half_pass.h",
     "source/opt/copy_prop_arrays.cpp",