Add support for GLSL interface blocks (#6351)

Adds support for input GLSL interface blocks.

closes #5535 

Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

2 files changed, 84 insertions, 36 deletions

diff --git a/source/slang/slang-ir-glsl-legalize.cpp b/source/slang/slang-ir-glsl-legalize.cpp
index 3ca441f96..67300dbe6 100644
--- a/source/slang/slang-ir-glsl-legalize.cpp
+++ b/source/slang/slang-ir-glsl-legalize.cpp
@@ -2923,6 +2923,22 @@ void tryReplaceUsesOfStageInput(
                                     fieldVal = element.val;
                                     break;
                                 }
+                                if (auto tupleValType =
+                                        as<ScalarizedTupleValImpl>(element.val.impl))
+                                {
+                                    for (auto tupleElement : tupleValType->elements)
+                                    {
+                                        if (tupleElement.key == fieldKey)
+                                        {
+                                            fieldVal = tupleElement.val;
+                                            break;
+                                        }
+                                    }
+                                }
+                                if (fieldVal.flavor != ScalarizedVal::Flavor::none)
+                                {
+                                    break;
+                                }
                             }
                             if (fieldVal.flavor != ScalarizedVal::Flavor::none)
                             {
@@ -3290,45 +3306,54 @@ void legalizeEntryPointParameterForGLSL(
             if (dec->getOp() != kIROp_GlobalVariableShadowingGlobalParameterDecoration)
                 continue;
             auto globalVar = dec->getOperand(0);
-            auto key = dec->getOperand(1);
-            IRInst* realGlobalVar = nullptr;
-            if (globalValue.flavor != ScalarizedVal::Flavor::tuple)
-                continue;
-            if (auto tupleVal = as<ScalarizedTupleValImpl>(globalValue.impl))
+            auto globalVarType = cast<IRPtrTypeBase>(globalVar->getDataType())->getValueType();
+            if (as<IRStructType>(globalVarType))
             {
-                for (auto elem : tupleVal->elements)
-                {
-                    if (elem.key == key)
-                    {
-                        realGlobalVar = elem.val.irValue;
-                        break;
-                    }
-                }
+                tryReplaceUsesOfStageInput(context, globalValue, globalVar);
             }
-            SLANG_ASSERT(realGlobalVar);
+            else
+            {
 
-            // Remove all stores into the global var introduced during
-            // the initial glsl global var translation pass since we are
-            // going to replace the global var with a pointer to the real
-            // input, and it makes no sense to store values into such real
-            // input locations.
-            traverseUses(
-                globalVar,
-                [&](IRUse* use)
+                auto key = dec->getOperand(1);
+                IRInst* realGlobalVar = nullptr;
+                if (globalValue.flavor != ScalarizedVal::Flavor::tuple)
+                    continue;
+                if (auto tupleVal = as<ScalarizedTupleValImpl>(globalValue.impl))
                 {
-                    auto user = use->getUser();
-                    if (auto store = as<IRStore>(user))
+                    for (auto elem : tupleVal->elements)
                     {
-                        if (store->getPtrUse() == use)
+                        if (elem.key == key)
                         {
-                            store->removeAndDeallocate();
+                            realGlobalVar = elem.val.irValue;
+                            break;
                         }
                     }
-                });
-            // we will be replacing uses of `globalVarToReplace`. We need
-            // globalVarToReplaceNextUse to catch the next use before it is removed from the
-            // list of uses.
-            globalVar->replaceUsesWith(realGlobalVar);
+                }
+                SLANG_ASSERT(realGlobalVar);
+
+                // Remove all stores into the global var introduced during
+                // the initial glsl global var translation pass since we are
+                // going to replace the global var with a pointer to the real
+                // input, and it makes no sense to store values into such real
+                // input locations.
+                traverseUses(
+                    globalVar,
+                    [&](IRUse* use)
+                    {
+                        auto user = use->getUser();
+                        if (auto store = as<IRStore>(user))
+                        {
+                            if (store->getPtrUse() == use)
+                            {
+                                store->removeAndDeallocate();
+                            }
+                        }
+                    });
+                // we will be replacing uses of `globalVarToReplace`. We need
+                // globalVarToReplaceNextUse to catch the next use before it is removed from the
+                // list of uses.
+                globalVar->replaceUsesWith(realGlobalVar);
+            }
             globalVar->removeAndDeallocate();
         }
     }
diff --git a/source/slang/slang-ir-translate-glsl-global-var.cpp b/source/slang/slang-ir-translate-glsl-global-var.cpp
index 7b2b8d1ee..80ed3c3e4 100644
--- a/source/slang/slang-ir-translate-glsl-global-var.cpp
+++ b/source/slang/slang-ir-translate-glsl-global-var.cpp
@@ -83,8 +83,26 @@ 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 +112,12 @@ 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 +158,8 @@ 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