WGSL: Fix issue where swizzle L-values are generated (shader-slang#5682)

* wgsl: Do not generate L-value swizzle expressions

* Enable tests/language-feature/swizzles/matrix-swizzle-write-*.slang

The following tests are enabled

- tests/language-feature/swizzles/matrix-swizzle-write-swizzle.slang
- tests/language-feature/swizzles/matrix-swizzle-write-array.slang

This closes shader-slang#5603.

source/slang/slang-emit-c-like.cpp

@@ -1661,15 +1661,16 @@ bool CLikeSourceEmitter::shouldFoldInstIntoUseSites(IRInst* inst)
         }
     }
 
-    // For cuda and cpu targets don't support swizzle on the left-hand-side
+    // The cpp, cuda and wgsl targets don't support swizzle on the left-hand-side
     // variable, e.g. vec4.xy = vec2 is not allowed.
     // Therefore, we don't want to fold the right-hand-side expression.
     // Instead, the right-hand-side expression should be generated as a separable
     // statement and stored in a temporary varible, then assign to the left-hand-side
     // variable per element. E.g. vec4.x = vec2.x; vec4.y = vec2.y.
     if (as<IRSwizzledStore>(user))
     {
-        if (isCPUTarget(getTargetReq()) || isCUDATarget(getTargetReq()))
+        if (isCPUTarget(getTargetReq()) || isCUDATarget(getTargetReq()) ||
+            isWGPUTarget(getTargetReq()))
             return false;
     }
 
@@ -3123,9 +3124,10 @@ void CLikeSourceEmitter::_emitInst(IRInst* inst)
 
     case kIROp_SwizzledStore:
         {
-            // cpp and cuda target don't support swizzle on the left handside, so we
+            // cpp, cuda and wgsl targets don't support swizzle on the left handside, so we
             // have to assign the element one by one.
-            if (isCPUTarget(getTargetReq()) || isCUDATarget(getTargetReq()))
+            if (isCPUTarget(getTargetReq()) || isCUDATarget(getTargetReq()) ||
+                isWGPUTarget(getTargetReq()))
             {
                 _emitSwizzleStorePerElement(inst);
             }

tests/expected-failure-github.txt

@@ -17,5 +17,3 @@ tests/language-feature/enums/strongly-typed-id.slang.1 syn (wgpu)
 tests/language-feature/generics/tuple.slang.1 syn (wgpu)
 tests/language-feature/generics/variadic-0.slang.4 syn (wgpu)
 tests/language-feature/shader-params/interface-shader-param-ordinary.slang.4 syn (wgpu)
-tests/language-feature/swizzles/matrix-swizzle-write-array.slang.3 syn (wgpu)
-tests/language-feature/swizzles/matrix-swizzle-write-swizzle.slang.3 syn (wgpu)

tests/language-feature/swizzles/matrix-swizzle-write-array.slang

@@ -1,8 +1,6 @@
 //TEST(compute):COMPARE_COMPUTE: -compute -shaderobj -output-using-type
 //TEST(compute, vulkan):COMPARE_COMPUTE: -vk -compute -shaderobj -output-using-type
 //TEST(compute):COMPARE_COMPUTE:-slang -shaderobj -mtl -output-using-type
-// WGSL: Assign to swizzle expression not allowed #5603
-//DISABLE_TEST(compute):COMPARE_COMPUTE_EX:-wgpu
 
 // Test that matrix swizzle writes work correctly
 // Matrix swizzles can either be one or zero indexed

tests/language-feature/swizzles/matrix-swizzle-write-swizzle.slang

@@ -1,8 +1,6 @@
 //TEST(compute):COMPARE_COMPUTE: -compute -shaderobj -output-using-type
 //TEST(compute, vulkan):COMPARE_COMPUTE: -vk -compute -shaderobj -output-using-type
 //TEST(compute):COMPARE_COMPUTE:-slang -shaderobj -mtl -output-using-type
-// WGSL: Assign to swizzle expression not allowed #5603
-//DISABLE_TEST(compute):COMPARE_COMPUTE_EX:-wgpu
 
 // Test that writing to swizzles of matrix swizzles works correctly