(Naga) Add support for Storage Image Multisample when ingesting SPIR-V (#8270)

CHANGELOG.md

@@ -200,6 +200,7 @@ By @cwfitzgerald in [#8162](https://github.com/gfx-rs/wgpu/pull/8162).
 - **BREAKING**: Previously the WGSL storage-texture format `rg11b10float` was incorrectly accepted and generated by naga, but now only accepts the the correct name `rg11b10ufloat` instead. By @ErikWDev in [#8219](https://github.com/gfx-rs/wgpu/pull/8219).
 - The [`source()`](https://doc.rust-lang.org/std/error/trait.Error.html#method.source) method of `ShaderError` no longer reports the error as its own source. By @andyleiserson in [#8258](https://github.com/gfx-rs/wgpu/pull/8258).
 - naga correctly ingests SPIR-V that use descriptor runtime indexing, which in turn is correctly converted into WGSLs binding array. By @hasenbanck in [8256](https://github.com/gfx-rs/wgpu/pull/8256).
+- naga correctly ingests SPIR-V that loads from multi-sampled textures, which in turn is correctly converted into WGSLs texture_multisampled_2d and load operations. By @hasenbanck in [8270](https://github.com/gfx-rs/wgpu/pull/8270).
  
 #### DX12
 

naga/src/front/spv/mod.rs

@@ -83,6 +83,7 @@ pub const SUPPORTED_CAPABILITIES: &[spirv::Capability] = &[
     spirv::Capability::GroupNonUniformShuffle,
     spirv::Capability::GroupNonUniformShuffleRelative,
     spirv::Capability::RuntimeDescriptorArray,
+    spirv::Capability::StorageImageMultisample,
     // tricky ones
     spirv::Capability::UniformBufferArrayDynamicIndexing,
     spirv::Capability::StorageBufferArrayDynamicIndexing,

naga/tests/in/spv/load-ms-texture.slang

@@ -0,0 +1,21 @@
+// Compiled with:
+// slangc -target spirv -profile spirv_1_5 -o naga/tests/in/spv/load-ms-texture.spv naga/tests/in/spv/load-ms-texture.slang
+// Disassembled with:
+// spirv-dis naga/tests/in/spv/load-ms-texture.spv -o naga/tests/in/spv/load-ms-texture.spvasm
+#language slang 2026
+
+[[vk::binding(0, 0)]] var texture: Texture2DMS;
+
+[[shader("pixel")]]
+func fs_main(float4 position : SV_Position) -> float4 {
+    let pixel_coord = int2(position.xy);
+    var color: float4;
+
+    for (var index: int = 0; index < 8; index++) {
+        color += texture.Load(pixel_coord, index);
+    }
+
+    color = color / 8.0;
+
+    return color;
+}

naga/tests/in/spv/load-ms-texture.spvasm

@@ -0,0 +1,93 @@
+; SPIR-V
+; Version: 1.5
+; Generator: Khronos Slang Compiler; 0
+; Bound: 65
+; Schema: 0
+               OpCapability StorageImageMultisample
+               OpCapability Shader
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint Fragment %fs_main "main" %texture %entryPointParam_fs_main %gl_FragCoord
+               OpExecutionMode %fs_main OriginUpperLeft
+               OpSource Slang 1
+               OpName %index "index"
+               OpName %index "index"
+               OpName %color "color"
+               OpName %color "color"
+               OpName %color_0 "color"
+               OpName %entryPointParam_fs_main "entryPointParam_fs_main"
+               OpName %texture "texture"
+               OpName %sampled "sampled"
+               OpName %color_1 "color"
+               OpName %fs_main "fs_main"
+               OpDecorate %gl_FragCoord BuiltIn FragCoord
+               OpDecorate %entryPointParam_fs_main Location 0
+               OpDecorate %texture Binding 0
+               OpDecorate %texture DescriptorSet 0
+       %void = OpTypeVoid
+          %3 = OpTypeFunction %void
+        %int = OpTypeInt 32 1
+%_ptr_Function_int = OpTypePointer Function %int
+      %float = OpTypeFloat 32
+    %v4float = OpTypeVector %float 4
+%_ptr_Function_v4float = OpTypePointer Function %v4float
+%_ptr_Input_v4float = OpTypePointer Input %v4float
+    %v2float = OpTypeVector %float 2
+      %v2int = OpTypeVector %int 2
+      %int_0 = OpConstant %int 0
+       %bool = OpTypeBool
+      %int_8 = OpConstant %int 8
+%_ptr_Output_v4float = OpTypePointer Output %v4float
+         %45 = OpTypeImage %float 2D 2 0 1 1 Unknown
+%_ptr_UniformConstant_45 = OpTypePointer UniformConstant %45
+      %int_1 = OpConstant %int 1
+%gl_FragCoord = OpVariable %_ptr_Input_v4float Input
+%entryPointParam_fs_main = OpVariable %_ptr_Output_v4float Output
+    %texture = OpVariable %_ptr_UniformConstant_45 UniformConstant
+%float_0_125 = OpConstant %float 0.125
+         %64 = OpConstantComposite %v4float %float_0_125 %float_0_125 %float_0_125 %float_0_125
+    %fs_main = OpFunction %void None %3
+          %4 = OpLabel
+      %index = OpVariable %_ptr_Function_int Function
+      %color = OpVariable %_ptr_Function_v4float Function
+         %22 = OpLoad %v4float %gl_FragCoord
+         %26 = OpVectorShuffle %v2float %22 %22 0 1
+         %28 = OpConvertFToS %v2int %26
+               OpStore %index %int_0
+               OpBranch %12
+         %12 = OpLabel
+               OpLoopMerge %17 %21 None
+               OpBranch %13
+         %13 = OpLabel
+               OpBranch %14
+         %14 = OpLabel
+               OpBranch %15
+         %15 = OpLabel
+         %31 = OpLoad %int %index
+         %33 = OpSLessThan %bool %31 %int_8
+               OpSelectionMerge %18 None
+               OpBranchConditional %33 %18 %16
+         %16 = OpLabel
+               OpBranch %17
+         %18 = OpLabel
+         %46 = OpLoad %45 %texture
+         %49 = OpLoad %int %index
+    %sampled = OpImageFetch %v4float %46 %28 Sample %49
+         %52 = OpLoad %v4float %color
+    %color_1 = OpFAdd %v4float %52 %sampled
+               OpBranch %19
+         %19 = OpLabel
+               OpBranch %20
+         %20 = OpLabel
+         %56 = OpLoad %int %index
+         %57 = OpIAdd %int %56 %int_1
+               OpStore %index %57
+               OpStore %color %color_1
+               OpBranch %21
+         %21 = OpLabel
+               OpBranch %12
+         %17 = OpLabel
+         %37 = OpLoad %v4float %color
+    %color_0 = OpFMul %v4float %37 %64
+               OpStore %entryPointParam_fs_main %color_0
+               OpReturn
+               OpFunctionEnd

naga/tests/in/spv/load-ms-texture.toml

@@ -0,0 +1,4 @@
+god_mode = true
+
+[spv-in]
+adjust_coordinate_space = true

naga/tests/out/wgsl/spv-load-ms-texture.wgsl

@@ -0,0 +1,37 @@
+var<private> global: vec4<f32>;
+var<private> entryPointParam_fs_main: vec4<f32>;
+@group(0) @binding(0) 
+var texture: texture_multisampled_2d<f32>;
+
+fn fs_main() {
+    var index: i32;
+    var color: vec4<f32>;
+
+    let _e9 = global;
+    index = 0i;
+    loop {
+        let _e12 = index;
+        if (_e12 < 8i) {
+        } else {
+            break;
+        }
+        let _e14 = index;
+        let _e15 = textureLoad(texture, vec2<i32>(_e9.xy), _e14);
+        let _e16 = color;
+        let _e18 = index;
+        index = (_e18 + 1i);
+        color = (_e16 + _e15);
+        continue;
+    }
+    let _e20 = color;
+    entryPointParam_fs_main = (_e20 * vec4<f32>(0.125f, 0.125f, 0.125f, 0.125f));
+    return;
+}
+
+@fragment 
+fn main(@builtin(position) param: vec4<f32>) -> @location(0) vec4<f32> {
+    global = param;
+    fs_main();
+    let _e3 = entryPointParam_fs_main;
+    return _e3;
+}