Fix invalid access mode for texture_buffer

Author: kaizhangNV

source/slang/slang-emit-metal.cpp

@@ -136,8 +136,15 @@ void MetalSourceEmitter::_emitHLSLTextureType(IRTextureTypeBase* texType)
     switch (texType->getAccess())
     {
     case SLANG_RESOURCE_ACCESS_READ:
-        m_writer->emit("access::sample");
-        break;
+        {
+            // Metal does not support access::sample for texture buffers, so we need to emit
+            // access::read instead.
+            if (texType->GetBaseShape() == SLANG_TEXTURE_BUFFER)
+                m_writer->emit("access::read");
+            else
+                m_writer->emit("access::sample");
+            break;
+        }
 
     case SLANG_RESOURCE_ACCESS_WRITE:
         m_writer->emit("access::write");

tests/metal/test_buffer.slang

@@ -0,0 +1,17 @@
+// Test that Buffer<T> maps to texture_buffer<uint, access::read> in Metal
+
+//TEST:SIMPLE(filecheck=METAL): -stage compute -entry computeMain -target metal
+
+
+// METAL: texture_buffer<uint, access::read> inputBuffer_{{.*}}
+Buffer<uint> inputBuffer;
+
+RWStructuredBuffer<uint> outputBuffer;
+
+[numthreads(4, 1, 1)]
+void computeMain(uint3 dtid : SV_DispatchThreadID)
+{
+    uint idx = dtid.x;
+    // Load values from the buffer to verify correct access
+    outputBuffer[idx] = inputBuffer.Load(idx);
+}