Add support for GLSL interface blocks

source/slang/slang-ir-glsl-legalize.cpp

@@ -3275,6 +3275,9 @@ void legalizeEntryPointParameterForGLSL(
             ptrType->getAddressSpace() == AddressSpace::Input ||
             ptrType->getAddressSpace() == AddressSpace::BuiltinInput);
 
+//DEBUG
+// printf("Before global value for varying input:\n");
+//pp->getModule()->getModuleInst()->dump();
         auto globalValue = createGLSLGlobalVaryings(
             context,
             codeGenContext,
@@ -3284,9 +3287,16 @@ void legalizeEntryPointParameterForGLSL(
             LayoutResourceKind::VaryingInput,
             stage,
             pp);
+
+// DEBUG
+// Dump IR
+//printf("Created global value for varying input:\n");
+// pp->getModule()->getModuleInst()->dump();
         tryReplaceUsesOfStageInput(context, globalValue, pp);
+#if 0
         for (auto dec : pp->getDecorations())
         {
+
             if (dec->getOp() != kIROp_GlobalVariableShadowingGlobalParameterDecoration)
                 continue;
             auto globalVar = dec->getOperand(0);
@@ -3298,13 +3308,34 @@ void legalizeEntryPointParameterForGLSL(
             {
                 for (auto elem : tupleVal->elements)
                 {
-                    if (elem.key == key)
+                    // check if elem is a tuple
+                    if (elem.val.flavor == ScalarizedVal::Flavor::tuple)
                     {
-                        realGlobalVar = elem.val.irValue;
-                        break;
+                        if (auto tupleVal = as<ScalarizedTupleValImpl>(elem.val.impl))
+                        {
+                            for (auto elem2 : tupleVal->elements)
+                            {
+                                if (elem2.key == key)
+                                {
+                                    realGlobalVar = elem2.val.irValue;
+                                    break;
+                                }
+                            }
+                        }
+                    }
+                    else
+                    {
+                        if (elem.key == key)
+                        {
+                            realGlobalVar = elem.val.irValue;
+                            break;
+                        }
                     }
                 }
             }
+
+//if (!realGlobalVar)
+//    printf("Warning: Could not find real global var for shadowing decoration\n");
             SLANG_ASSERT(realGlobalVar);
 
             // Remove all stores into the global var introduced during
@@ -3331,6 +3362,12 @@ void legalizeEntryPointParameterForGLSL(
             globalVar->replaceUsesWith(realGlobalVar);
             globalVar->removeAndDeallocate();
         }
+
+// Dump IR
+//printf("Replaced global accessed with shadow:\n");
+//pp->getModule()->getModuleInst()->dump();
+//printf("printed\n");
+#endif
     }
     else
     {

source/slang/slang-ir-translate-glsl-global-var.cpp

@@ -83,8 +83,25 @@ struct GlobalVarTranslationContext
                 auto key = builder.createStructKey();
                 inputKeys.add(key);
                 builder.createStructField(inputStructType, key, inputType);
-                IRTypeLayout::Builder fieldTypeLayout(&builder);
-                IRVarLayout::Builder varLayoutBuilder(&builder, fieldTypeLayout.build());
+
+                IRTypeLayout::Builder fieldTypeLayoutBuilder(&builder);
+                IRTypeLayout* fieldTypeLayout = nullptr;
+                bool hasExistingLayout = false;
+                if (auto existingLayoutDecoration = input->findDecoration<IRLayoutDecoration>())
+                {
+                    if (auto existingVarLayout = as<IRVarLayout>(existingLayoutDecoration->getLayout()))                        
+                    {
+                        fieldTypeLayout = existingVarLayout->getTypeLayout();
+                        hasExistingLayout = true;
+                    }
+                }
+
+                if (!hasExistingLayout)
+                {
+                    fieldTypeLayout = fieldTypeLayoutBuilder.build();
+                }
+
+                IRVarLayout::Builder varLayoutBuilder(&builder, fieldTypeLayout);
                 varLayoutBuilder.setStage(entryPointDecor->getProfile().getStage());
                 if (auto semanticDecor = input->findDecoration<IRSemanticDecoration>())
                 {
@@ -94,9 +111,12 @@ struct GlobalVarTranslationContext
                 }
                 else
                 {
-                    fieldTypeLayout.addResourceUsage(
-                        LayoutResourceKind::VaryingInput,
-                        LayoutSize(1));
+                    if (!hasExistingLayout)
+                    {
+                        fieldTypeLayoutBuilder.addResourceUsage(
+                            LayoutResourceKind::VaryingInput,
+                            LayoutSize(1));
+                    }                    
                     if (auto layoutDecor = findVarLayout(input))
                     {
                         if (auto offsetAttr =
@@ -137,6 +157,8 @@ struct GlobalVarTranslationContext
                 auto input = inputVars[i];
                 setInsertBeforeOrdinaryInst(&builder, firstBlock->getFirstOrdinaryInst());
                 auto inputType = cast<IRPtrTypeBase>(input->getDataType())->getValueType();
+                // TODO: This could be more efficient as a Load(FieldAddress(inputParam, i))
+                // operation instead of a FieldExtract(Load(inputParam)).
                 builder.emitStore(
                     input,
                     builder

tests/glsl/interface-block.glsl

@@ -0,0 +1,37 @@
+//TEST:SIMPLE(filecheck=CHECK_GLSL): -target glsl -stage fragment -entry fragmentMain -allow-glsl
+
+//CHECK_GLSL: layout(location = 0)
+//CHECK_GLSL: out vec4 entryPointParam_fragmentMain_out1_0;
+
+//CHECK_GLSL: layout(location = 0)
+//CHECK_GLSL: in vec2 vd_texcoord_0_0;
+
+//CHECK_GLSL: layout(location = 1)
+//CHECK_GLSL: in vec2 vd_texcoord_1_0;
+
+//CHECK_GLSL: layout(location = 2)
+//CHECK_GLSL: in vec4 vd_inner_texcoord_2_0;
+
+import glsl;
+
+#version 400
+
+struct innerData
+{
+    vec4 texcoord_2;
+};
+
+in VertexData
+{
+    vec2 texcoord_0;
+    vec2 texcoord_1;
+    innerData inner;
+} vd;
+
+out vec4 out1;
+
+void fragmentMain()
+{
+    out1 = vec4(vd.texcoord_0, vd.texcoord_1.x, vd.inner.texcoord_2.y);
+}
+