SPIRV: Fix performance issue when handling large arrays. (#4064)

* SPIRV: Fix performance issue when handling large arrays.

* Add test for packing.

* Fix clang.

3 files changed, 11 insertions, 1 deletions

diff --git a/tools/render-test/render-test-main.cpp b/tools/render-test/render-test-main.cpp
index 02c0ea86a..fcdd4b54d 100644
--- a/tools/render-test/render-test-main.cpp
+++ b/tools/render-test/render-test-main.cpp
@@ -207,7 +207,10 @@ struct AssignValsFromLayoutContext
     {
         const InputBufferDesc& srcBuffer = srcVal->bufferDesc;
         auto& bufferData = srcVal->bufferData;
-        const size_t bufferSize = bufferData.getCount() * sizeof(uint32_t);
+        const size_t bufferSize = Math::Max((size_t)bufferData.getCount() * sizeof(uint32_t), (size_t)(srcBuffer.elementCount * srcBuffer.stride));
+        bufferData.reserve(bufferSize / sizeof(uint32_t));
+        for (size_t i = bufferData.getCount(); i < bufferSize / sizeof(uint32_t); i++)
+            bufferData.add(0);
 
         ComPtr<IBufferResource> bufferResource;
         SLANG_RETURN_ON_FAIL(ShaderRendererUtil::createBufferResource(srcBuffer, /*entry.isOutput,*/ bufferSize, bufferData.getBuffer(), device, bufferResource));
@@ -232,6 +235,7 @@ struct AssignValsFromLayoutContext
                 const InputBufferDesc& counterBufferDesc{
                     InputBufferType::StorageBuffer,
                     sizeof(uint32_t),
+                    1,
                     Format::Unknown,
                 };
                 SLANG_RETURN_ON_FAIL(ShaderRendererUtil::createBufferResource(
diff --git a/tools/render-test/shader-input-layout.cpp b/tools/render-test/shader-input-layout.cpp
index 96f5db6e0..3012d45a4 100644
--- a/tools/render-test/shader-input-layout.cpp
+++ b/tools/render-test/shader-input-layout.cpp
@@ -222,6 +222,11 @@ namespace renderer_test
                 parser.Read("=");
                 val->bufferDesc.stride = parser.ReadInt();
             }
+            else if (word == "count")
+            {
+                parser.Read("=");
+                val->bufferDesc.elementCount = parser.ReadInt();
+            }
             else if (word == "counter")
             {
                 parser.Read("=");
diff --git a/tools/render-test/shader-input-layout.h b/tools/render-test/shader-input-layout.h
index de1da3da9..996635b94 100644
--- a/tools/render-test/shader-input-layout.h
+++ b/tools/render-test/shader-input-layout.h
@@ -68,6 +68,7 @@ struct InputBufferDesc
 {
     InputBufferType type = InputBufferType::StorageBuffer;
     int stride = 0; // stride == 0 indicates an unstructured buffer.
+    int elementCount = 1;
     Format format = Format::Unknown;
     // For RWStructuredBuffer, AppendStructuredBuffer, ConsumeStructuredBuffer
     // the default value of 0xffffffff indicates that a counter buffer should