Properly plumbing layout for global varyings. (#6198)

* Properly plumbing layout for global varyings.

* Fix test.

6 files changed, 106 insertions, 31 deletions

diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index 3453d0538..33319ca8f 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -842,26 +842,29 @@ bool isGlobalShaderParameter(VarDeclBase* decl)
     if (!isGlobalDecl(decl))
         return false;
 
-    // A global variable marked `static` indicates a traditional
-    // global variable (albeit one that is implicitly local to
-    // the translation unit)
-    //
-    if (decl->hasModifier<HLSLStaticModifier>())
-        return false;
+    for (auto modifier : decl->modifiers)
+    {
+        // A global variable marked `static` indicates a traditional
+        // global variable (albeit one that is implicitly local to
+        // the translation unit)
+        //
+        if (as<HLSLStaticModifier>(modifier))
+            return false;
 
-    // While not normally allowed, out variables are not constant
-    // parameters, this can happen for example in GLSL mode
-    if (decl->hasModifier<OutModifier>())
-        return false;
-    if (decl->hasModifier<InModifier>())
-        return false;
+        // While not normally allowed, out variables are not constant
+        // parameters, this can happen for example in GLSL mode
+        if (as<OutModifier>(modifier))
+            return false;
+        if (as<InModifier>(modifier))
+            return false;
 
-    // The `groupshared` modifier indicates that a variable cannot
-    // be a shader parameters, but is instead transient storage
-    // allocated for the duration of a thread-group's execution.
-    //
-    if (decl->hasModifier<HLSLGroupSharedModifier>())
-        return false;
+        // The `groupshared` modifier indicates that a variable cannot
+        // be a shader parameters, but is instead transient storage
+        // allocated for the duration of a thread-group's execution.
+        //
+        if (as<HLSLGroupSharedModifier>(modifier))
+            return false;
+    }
 
     return true;
 }
diff --git a/source/slang/slang-check-shader.cpp b/source/slang/slang-check-shader.cpp
index c9e190469..d04c72e15 100644
--- a/source/slang/slang-check-shader.cpp
+++ b/source/slang/slang-check-shader.cpp
@@ -741,7 +741,19 @@ void Module::_collectShaderParams()
                 // things like `static` globals and `groupshared` variables.
                 //
                 if (!isGlobalShaderParameter(globalVar))
-                    continue;
+                {
+                    bool isVarying = false;
+                    for (auto m : globalVar->modifiers)
+                    {
+                        if (as<InModifier>(m) || as<OutModifier>(m))
+                        {
+                            isVarying = true;
+                            break;
+                        }
+                    }
+                    if (!isVarying)
+                        continue;
+                }
 
                 // At this point we know we have a global shader parameter.
 
diff --git a/source/slang/slang-ir-translate-glsl-global-var.cpp b/source/slang/slang-ir-translate-glsl-global-var.cpp
index 077cdb98d..7b2b8d1ee 100644
--- a/source/slang/slang-ir-translate-glsl-global-var.cpp
+++ b/source/slang/slang-ir-translate-glsl-global-var.cpp
@@ -86,11 +86,6 @@ struct GlobalVarTranslationContext
                 IRTypeLayout::Builder fieldTypeLayout(&builder);
                 IRVarLayout::Builder varLayoutBuilder(&builder, fieldTypeLayout.build());
                 varLayoutBuilder.setStage(entryPointDecor->getProfile().getStage());
-                if (auto locationDecoration = input->findDecoration<IRGLSLLocationDecoration>())
-                {
-                    varLayoutBuilder.findOrAddResourceInfo(LayoutResourceKind::VaryingInput)
-                        ->offset = (UInt)getIntVal(locationDecoration->getLocation());
-                }
                 if (auto semanticDecor = input->findDecoration<IRSemanticDecoration>())
                 {
                     varLayoutBuilder.setSystemValueSemantic(
@@ -102,6 +97,16 @@ struct GlobalVarTranslationContext
                     fieldTypeLayout.addResourceUsage(
                         LayoutResourceKind::VaryingInput,
                         LayoutSize(1));
+                    if (auto layoutDecor = findVarLayout(input))
+                    {
+                        if (auto offsetAttr =
+                                layoutDecor->findOffsetAttr(LayoutResourceKind::VaryingInput))
+                        {
+                            varLayoutBuilder
+                                .findOrAddResourceInfo(LayoutResourceKind::VaryingInput)
+                                ->offset = (UInt)offsetAttr->getOffset();
+                        }
+                    }
                     if (entryPointDecor->getProfile().getStage() == Stage::Fragment)
                     {
                         varLayoutBuilder.setUserSemantic("COLOR", inputVarIndex);
@@ -180,13 +185,15 @@ struct GlobalVarTranslationContext
                         fieldTypeLayout.addResourceUsage(
                             LayoutResourceKind::VaryingOutput,
                             LayoutSize(1));
-
-                        if (auto locationDecoration =
-                                output->findDecoration<IRGLSLLocationDecoration>())
+                        if (auto layoutDecor = findVarLayout(output))
                         {
-                            varLayoutBuilder
-                                .findOrAddResourceInfo(LayoutResourceKind::VaryingOutput)
-                                ->offset = (UInt)getIntVal(locationDecoration->getLocation());
+                            if (auto offsetAttr =
+                                    layoutDecor->findOffsetAttr(LayoutResourceKind::VaryingOutput))
+                            {
+                                varLayoutBuilder
+                                    .findOrAddResourceInfo(LayoutResourceKind::VaryingOutput)
+                                    ->offset = (UInt)offsetAttr->getOffset();
+                            }
                         }
                         if (entryPointDecor->getProfile().getStage() == Stage::Fragment)
                         {
diff --git a/source/slang/slang-lower-to-ir.cpp b/source/slang/slang-lower-to-ir.cpp
index a12a09a2b..7281b55be 100644
--- a/source/slang/slang-lower-to-ir.cpp
+++ b/source/slang/slang-lower-to-ir.cpp
@@ -12209,7 +12209,9 @@ RefPtr<IRModule> TargetProgram::createIRModuleForLayout(DiagnosticSink* sink)
         // has been emitted to this module, so that we will have something
         // to decorate.
         //
-        auto irVar = getSimpleVal(context, ensureDecl(context, varDecl.getDecl()));
+        auto irVar = materialize(context, ensureDecl(context, varDecl.getDecl())).val;
+        if (!irVar)
+            SLANG_UNEXPECTED("unhandled value flavor");
 
         auto irLayout = lowerVarLayout(context, varLayout);
 
diff --git a/source/slang/slang-parameter-binding.cpp b/source/slang/slang-parameter-binding.cpp
index 825e0f4af..55c487e4e 100644
--- a/source/slang/slang-parameter-binding.cpp
+++ b/source/slang/slang-parameter-binding.cpp
@@ -712,6 +712,15 @@ RefPtr<TypeLayout> getTypeLayoutForGlobalShaderParameter(
         return createTypeLayoutWith(layoutContext, specializationConstantRule, type);
     }
 
+    if (varDecl->hasModifier<InModifier>())
+    {
+        return createTypeLayoutWith(layoutContext, rules->getVaryingInputRules(), type);
+    }
+    else if (varDecl->hasModifier<OutModifier>())
+    {
+        return createTypeLayoutWith(layoutContext, rules->getVaryingOutputRules(), type);
+    }
+
     // TODO(tfoley): there may be other cases that we need to handle here
 
     // An "ordinary" global variable is implicitly a uniform
@@ -1120,6 +1129,25 @@ static void addExplicitParameterBindings_GLSL(
             return;
     }
 
+    if (auto foundVaryingInput = typeLayout->FindResourceInfo(LayoutResourceKind::VaryingInput))
+    {
+        info[kResInfo].resInfo = foundVaryingInput;
+
+        if (auto layoutAttr = varDecl.getDecl()->findModifier<GLSLLocationAttribute>())
+            info[kResInfo].semanticInfo.index = layoutAttr->value;
+        else
+            return;
+    }
+    if (auto foundVaryingOutput = typeLayout->FindResourceInfo(LayoutResourceKind::VaryingOutput))
+    {
+        info[kResInfo].resInfo = foundVaryingOutput;
+
+        if (auto layoutAttr = varDecl.getDecl()->findModifier<GLSLLocationAttribute>())
+            info[kResInfo].semanticInfo.index = layoutAttr->value;
+        else
+            return;
+    }
+
     // For remaining cases, we only want to apply GLSL-style layout modifers
     // when compiling for Khronos and WGSL targets.
     //
diff --git a/tests/glsl/in-layout.slang b/tests/glsl/in-layout.slang
new file mode 100644
index 000000000..651948c69
--- /dev/null
+++ b/tests/glsl/in-layout.slang
@@ -0,0 +1,23 @@
+//TEST:SIMPLE(filecheck=CHECK): -target spirv -entry main -stage fragment
+
+// Test that we can mix explicit and implicit locations for global varyings.
+
+#version 450
+layout(location=1) in vec4 color_0;
+in vec2 texcoord_0;
+in vec2 texCoord_1;
+
+out vec4 out1;
+
+// CHECK-DAG: OpDecorate %color_0 Location 1
+
+// CHECK-DAG: OpDecorate %texcoord_0 Location 0
+
+// CHECK-DAG: OpDecorate %texCoord_1 Location 2
+
+// CHECK-DAG: OpDecorate %entryPointParam_main_out1 Location 0
+
+void main()
+{
+    out1 = vec4(color_0.rg, texcoord_0 + texCoord_1);
+}
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