Fix spurious StorageImageReadWithoutFormat capability for write-only textures

source/slang/slang-emit-spirv.cpp

@@ -3073,9 +3073,10 @@ struct SPIRVEmitContext : public SourceEmitterBase, public SPIRVEmitSharedContex
         }
         if (format == SpvImageFormatUnknown && sampled == ImageOpConstants::readWriteImage)
         {
-            // TODO: It may not be necessary to have both of these
-            // depending on if we read or write
-            requireSPIRVCapability(SpvCapabilityStorageImageReadWithoutFormat);
+            // Write-only textures (WTexture*) only need the write capability.
+            // Read-write and rasterizer-ordered textures need both.
+            if (inst->getAccess() != SLANG_RESOURCE_ACCESS_WRITE)
+                requireSPIRVCapability(SpvCapabilityStorageImageReadWithoutFormat);
             requireSPIRVCapability(SpvCapabilityStorageImageWriteWithoutFormat);
         }
 

tests/spirv/read-write-image-capability.slang

@@ -0,0 +1,18 @@
+//TEST:SIMPLE(filecheck=CHECK):-target spirv -emit-spirv-directly
+
+// When using a read-write texture (RWTexture2D) without an explicit format,
+// both StorageImageReadWithoutFormat and StorageImageWriteWithoutFormat
+// should be required.
+// Companion to write-only-image-capability.slang.
+
+// CHECK-DAG: OpCapability StorageImageReadWithoutFormat
+// CHECK-DAG: OpCapability StorageImageWriteWithoutFormat
+
+RWTexture2D<float4> rwTexture;
+
+[shader("compute")]
+[numthreads(1, 1, 1)]
+void computeMain()
+{
+    rwTexture[int2(0, 0)] = rwTexture[int2(1, 1)];
+}

tests/spirv/write-only-image-capability.slang

@@ -0,0 +1,20 @@
+//TEST:SIMPLE(filecheck=CHECK):-target spirv -emit-spirv-directly
+
+// When using a write-only texture (WTexture2D) without an explicit format,
+// only StorageImageWriteWithoutFormat should be required, not
+// StorageImageReadWithoutFormat.
+// See: https://github.com/shader-slang/slang/issues/9997
+
+// CHECK-NOT: OpCapability StorageImageReadWithoutFormat
+// CHECK: OpCapability StorageImageWriteWithoutFormat
+// CHECK: OpDecorate {{.*}} NonReadable
+// CHECK-NOT: OpCapability StorageImageReadWithoutFormat
+
+WTexture2D<float4> writeOnlyTexture;
+
+[shader("compute")]
+[numthreads(1, 1, 1)]
+void computeMain()
+{
+    writeOnlyTexture.Store(int2(0, 0), float4(0, 0, 0, 1));
+}