Support link-time constants. (#3564)

* Support link-time constants.

* Fix.

* Fix.

9 files changed, 229 insertions, 17 deletions

diff --git a/build/visual-studio/gfx-unit-test-tool/gfx-unit-test-tool.vcxproj b/build/visual-studio/gfx-unit-test-tool/gfx-unit-test-tool.vcxproj
index 5cd61e7fe..335fa8156 100644
--- a/build/visual-studio/gfx-unit-test-tool/gfx-unit-test-tool.vcxproj
+++ b/build/visual-studio/gfx-unit-test-tool/gfx-unit-test-tool.vcxproj
@@ -303,6 +303,7 @@
     <ClCompile Include="..\..\..\tools\gfx-unit-test\gfx-test-texture-util.cpp" />

     <ClCompile Include="..\..\..\tools\gfx-unit-test\gfx-test-util.cpp" />

     <ClCompile Include="..\..\..\tools\gfx-unit-test\instanced-draw-tests.cpp" />

+    <ClCompile Include="..\..\..\tools\gfx-unit-test\link-time-constant.cpp" />

     <ClCompile Include="..\..\..\tools\gfx-unit-test\mutable-shader-object.cpp" />

     <ClCompile Include="..\..\..\tools\gfx-unit-test\nested-parameter-block.cpp" />

     <ClCompile Include="..\..\..\tools\gfx-unit-test\ray-tracing-tests.cpp" />

@@ -323,6 +324,7 @@
     <None Include="..\..\..\tools\gfx-unit-test\compute-trivial.slang" />

     <None Include="..\..\..\tools\gfx-unit-test\format-test-shaders.slang" />

     <None Include="..\..\..\tools\gfx-unit-test\graphics-smoke.slang" />

+    <None Include="..\..\..\tools\gfx-unit-test\link-time-constant.slang" />

     <None Include="..\..\..\tools\gfx-unit-test\mutable-shader-object.slang" />

     <None Include="..\..\..\tools\gfx-unit-test\nested-parameter-block.slang" />

     <None Include="..\..\..\tools\gfx-unit-test\ray-tracing-test-shaders.slang" />

diff --git a/build/visual-studio/gfx-unit-test-tool/gfx-unit-test-tool.vcxproj.filters b/build/visual-studio/gfx-unit-test-tool/gfx-unit-test-tool.vcxproj.filters
index 58045ccee..fa5ca30e5 100644
--- a/build/visual-studio/gfx-unit-test-tool/gfx-unit-test-tool.vcxproj.filters
+++ b/build/visual-studio/gfx-unit-test-tool/gfx-unit-test-tool.vcxproj.filters
@@ -65,6 +65,9 @@
     <ClCompile Include="..\..\..\tools\gfx-unit-test\instanced-draw-tests.cpp">

       <Filter>Source Files</Filter>

     </ClCompile>

+    <ClCompile Include="..\..\..\tools\gfx-unit-test\link-time-constant.cpp">

+      <Filter>Source Files</Filter>

+    </ClCompile>

     <ClCompile Include="..\..\..\tools\gfx-unit-test\mutable-shader-object.cpp">

       <Filter>Source Files</Filter>

     </ClCompile>

@@ -121,6 +124,9 @@
     <None Include="..\..\..\tools\gfx-unit-test\graphics-smoke.slang">

       <Filter>Source Files</Filter>

     </None>

+    <None Include="..\..\..\tools\gfx-unit-test\link-time-constant.slang">

+      <Filter>Source Files</Filter>

+    </None>

     <None Include="..\..\..\tools\gfx-unit-test\mutable-shader-object.slang">

       <Filter>Source Files</Filter>

     </None>

diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index 3882994da..2a6ee8abc 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -1471,6 +1471,11 @@ namespace Slang
             }
             else
             {
+                if (varDecl->hasModifier<ExternModifier>())
+                {
+                    getSink()->diagnose(initExpr, Diagnostics::externValueCannotHaveInitializer);
+                }
+
                 initExpr = CheckExpr(initExpr);
 
                 // TODO: We might need some additional steps here to ensure
@@ -1484,7 +1489,7 @@ namespace Slang
 
                 _validateCircularVarDefinition(varDecl);
             }
-
+            
             // If we've gone down this path, then the variable
             // declaration is actually pretty far along in checking
             varDecl->setCheckState(DeclCheckState::DefinitionChecked);
diff --git a/source/slang/slang-check-expr.cpp b/source/slang/slang-check-expr.cpp
index 2f4906826..c04cb73e4 100644
--- a/source/slang/slang-check-expr.cpp
+++ b/source/slang/slang-check-expr.cpp
@@ -1659,6 +1659,9 @@ namespace Slang
             return nullptr;
         if(!decl->hasModifier<ConstModifier>())
             return nullptr;
+        // Extern static const is not considered compile-time constant by the front-end.
+        if (decl->hasModifier<ExternModifier>())
+            return nullptr;
 
         if (isInterfaceRequirement(decl))
         {
diff --git a/source/slang/slang-diagnostic-defs.h b/source/slang/slang-diagnostic-defs.h
index 9b599ae2e..ac1f9aff9 100644
--- a/source/slang/slang-diagnostic-defs.h
+++ b/source/slang/slang-diagnostic-defs.h
@@ -478,10 +478,10 @@ DIAGNOSTIC(30502, Error, cannotUseInitializerListForVectorOfUnknownSize, "cannot
 DIAGNOSTIC(30503, Error, cannotUseInitializerListForMatrixOfUnknownSize, "cannot use initializer list for matrix of statically unknown size '$0' rows")
 DIAGNOSTIC(30504, Error, cannotUseInitializerListForType, "cannot use initializer list for type '$0'")
 
-// 306xx: variables
-DIAGNOSTIC(30600, Error, varWithoutTypeMustHaveInitializer, "a variable declaration without an initial-value expression must be given an explicit type")
-
-DIAGNOSTIC(30610, Error, ambiguousDefaultInitializerForType, "more than one default initializer was found for type '$0'")
+// 3062x: variables
+DIAGNOSTIC(30620, Error, varWithoutTypeMustHaveInitializer, "a variable declaration without an initial-value expression must be given an explicit type")
+DIAGNOSTIC(30621, Error, externValueCannotHaveInitializer, "an 'extern' variable declaration cannot have a value.")
+DIAGNOSTIC(30622, Error, ambiguousDefaultInitializerForType, "more than one default initializer was found for type '$0'")
 
 // 307xx: parameters
 DIAGNOSTIC(30700, Error, outputParameterCannotHaveDefaultValue, "an 'out' or 'inout' parameter cannot have a default-value expression")
diff --git a/source/slang/slang-mangle.cpp b/source/slang/slang-mangle.cpp
index 3f701f385..9431533ac 100644
--- a/source/slang/slang-mangle.cpp
+++ b/source/slang/slang-mangle.cpp
@@ -132,7 +132,8 @@ namespace Slang
 
     void emitQualifiedName(
         ManglingContext*    context,
-        DeclRef<Decl>       declRef);
+        DeclRef<Decl>       declRef,
+        bool includeModuleName);
 
     void emitSimpleIntVal(
         ManglingContext*    context,
@@ -211,7 +212,7 @@ namespace Slang
         }
         else if( auto declRefType = dynamicCast<DeclRefType>(type) )
         {
-            emitQualifiedName(context, declRefType->getDeclRef());
+            emitQualifiedName(context, declRefType->getDeclRef(), true);
         }
         else if (auto arrType = dynamicCast<ArrayExpressionType>(type))
         {
@@ -222,7 +223,7 @@ namespace Slang
         else if( auto thisType = dynamicCast<ThisType>(type) )
         {
             emitRaw(context, "t");
-            emitQualifiedName(context, thisType->getInterfaceDeclRef());
+            emitQualifiedName(context, thisType->getInterfaceDeclRef(), true);
         }
         else if (const auto errorType = dynamicCast<ErrorType>(type))
         {
@@ -356,8 +357,26 @@ namespace Slang
 
     void emitQualifiedName(
         ManglingContext*    context,
-        DeclRef<Decl>       declRef)
+        DeclRef<Decl>       declRef,
+        bool includeModuleName)
     {
+        if (!includeModuleName)
+        {
+            if (as<ModuleDecl>(declRef))
+                return;
+        }
+        else
+        {
+            for (auto modifier : declRef.getDecl()->modifiers)
+            {
+                if (as<ExternModifier>(modifier) || as<HLSLExportModifier>(modifier))
+                {
+                    includeModuleName = false;
+                    break;
+                }
+            }
+        }
+
         auto parentDeclRef = declRef.getParent();
         if (as<FileDecl>(parentDeclRef))
             parentDeclRef = parentDeclRef.getParent();
@@ -365,7 +384,7 @@ namespace Slang
         auto parentGenericDeclRef = parentDeclRef.as<GenericDecl>();
         if( parentDeclRef )
         {
-            emitQualifiedName(context, parentDeclRef);
+            emitQualifiedName(context, parentDeclRef, includeModuleName);
         }
 
         // A generic declaration is kind of a pseudo-declaration
@@ -490,7 +509,7 @@ namespace Slang
                     for (auto type : constraint.value)
                     {
                         emitRaw(context, "C");
-                        emitQualifiedName(context, makeDeclRef(constraint.key));
+                        emitQualifiedName(context, makeDeclRef(constraint.key), true);
                             emitType(context, type);
                     }
                 }
@@ -579,7 +598,7 @@ namespace Slang
 
             auto innerDecl = getInner(genericDecl);
 
-            emitQualifiedName(context, makeDeclRef(innerDecl));
+            emitQualifiedName(context, makeDeclRef(innerDecl), true);
             return;
         }
         else if (as<ForwardDerivativeRequirementDecl>(decl))
@@ -592,7 +611,8 @@ namespace Slang
         }
 
         // Now we encode the qualified name of the decl.
-        emitQualifiedName(context, declRef);
+        
+        emitQualifiedName(context, declRef, true);
     }
 
     static String getMangledName(ASTBuilder* astBuilder, DeclRef<Decl> const& declRef)
@@ -625,8 +645,8 @@ namespace Slang
         SLANG_AST_BUILDER_RAII(astBuilder);
         ManglingContext context(astBuilder);
         emitRaw(&context, "_SW");
-        emitQualifiedName(&context, sub);
-        emitQualifiedName(&context, sup);
+        emitQualifiedName(&context, sub, true);
+        emitQualifiedName(&context, sup, true);
         return context.sb.produceString();
     }
 
@@ -643,7 +663,7 @@ namespace Slang
         //
         ManglingContext context(astBuilder);
         emitRaw(&context, "_SW");
-        emitQualifiedName(&context, sub);
+        emitQualifiedName(&context, sub, true);
         emitType(&context, sup);
         return context.sb.produceString();
     }
diff --git a/tools/gfx-unit-test/gfx-test-util.h b/tools/gfx-unit-test/gfx-test-util.h
index 22b9b2fd3..501deeae0 100644
--- a/tools/gfx-unit-test/gfx-test-util.h
+++ b/tools/gfx-unit-test/gfx-test-util.h
@@ -8,7 +8,7 @@
 namespace gfx_test
 {
         /// Helper function for print out diagnostic messages output by Slang compiler.
-    void diagnoseIfNeeded(ISlangWriter* diagnosticWriter, slang::IBlob* diagnosticsBlob);
+    void diagnoseIfNeeded(slang::IBlob* diagnosticsBlob);
 
         /// Loads a compute shader module and produces a `gfx::IShaderProgram`.
     Slang::Result loadComputeProgram(
diff --git a/tools/gfx-unit-test/link-time-constant.cpp b/tools/gfx-unit-test/link-time-constant.cpp
new file mode 100644
index 000000000..62cb294c1
--- /dev/null
+++ b/tools/gfx-unit-test/link-time-constant.cpp
@@ -0,0 +1,156 @@
+#include "tools/unit-test/slang-unit-test.h"
+
+#include "slang-gfx.h"
+#include "gfx-test-util.h"
+#include "tools/gfx-util/shader-cursor.h"
+#include "source/core/slang-basic.h"
+#include "source/core/slang-blob.h"
+
+using namespace gfx;
+
+namespace gfx_test
+{
+    static Slang::Result loadProgram(
+        gfx::IDevice* device,
+        Slang::ComPtr<gfx::IShaderProgram>& outShaderProgram,
+        const char* shaderModuleName,
+        const char* entryPointName,
+        slang::ProgramLayout*& slangReflection,
+        const char* additionalModuleSource)
+    {
+        Slang::ComPtr<slang::ISession> slangSession;
+        SLANG_RETURN_ON_FAIL(device->getSlangSession(slangSession.writeRef()));
+        Slang::ComPtr<slang::IBlob> diagnosticsBlob;
+        slang::IModule* module = slangSession->loadModule(shaderModuleName, diagnosticsBlob.writeRef());
+        diagnoseIfNeeded(diagnosticsBlob);
+        if (!module)
+            return SLANG_FAIL;
+
+        auto additionalModuleBlob = Slang::UnownedRawBlob::create(additionalModuleSource, strlen(additionalModuleSource));
+        slang::IModule* additionalModule = slangSession->loadModuleFromSource("linkedConstants", "path",
+            additionalModuleBlob);
+
+        ComPtr<slang::IEntryPoint> computeEntryPoint;
+        SLANG_RETURN_ON_FAIL(
+            module->findEntryPointByName(entryPointName, computeEntryPoint.writeRef()));
+
+        Slang::List<slang::IComponentType*> componentTypes;
+        componentTypes.add(module);
+        componentTypes.add(computeEntryPoint);
+        componentTypes.add(additionalModule);
+
+        Slang::ComPtr<slang::IComponentType> composedProgram;
+        SlangResult result = slangSession->createCompositeComponentType(
+            componentTypes.getBuffer(),
+            componentTypes.getCount(),
+            composedProgram.writeRef(),
+            diagnosticsBlob.writeRef());
+        diagnoseIfNeeded(diagnosticsBlob);
+        SLANG_RETURN_ON_FAIL(result);
+
+        ComPtr<slang::IComponentType> linkedProgram;
+        result = composedProgram->link(linkedProgram.writeRef(), diagnosticsBlob.writeRef());
+        diagnoseIfNeeded(diagnosticsBlob);
+        SLANG_RETURN_ON_FAIL(result);
+
+        composedProgram = linkedProgram;
+        slangReflection = composedProgram->getLayout();
+
+        gfx::IShaderProgram::Desc programDesc = {};
+        programDesc.slangGlobalScope = composedProgram.get();
+
+        auto shaderProgram = device->createProgram(programDesc);
+
+        outShaderProgram = shaderProgram;
+        return SLANG_OK;
+    }
+
+    void linkTimeConstantTestImpl(IDevice* device, UnitTestContext* context)
+    {
+        Slang::ComPtr<ITransientResourceHeap> transientHeap;
+        ITransientResourceHeap::Desc transientHeapDesc = {};
+        transientHeapDesc.constantBufferSize = 4096;
+        GFX_CHECK_CALL_ABORT(
+            device->createTransientResourceHeap(transientHeapDesc, transientHeap.writeRef()));
+
+        ComPtr<IShaderProgram> shaderProgram;
+        slang::ProgramLayout* slangReflection;
+        GFX_CHECK_CALL_ABORT(loadProgram(device, shaderProgram, "link-time-constant", "computeMain", slangReflection, 
+            R"(
+                export static const bool turnOnFeature = true;
+                export static const float constValue = 2.0;
+            )"));
+
+        ComputePipelineStateDesc pipelineDesc = {};
+        pipelineDesc.program = shaderProgram.get();
+        ComPtr<gfx::IPipelineState> pipelineState;
+        GFX_CHECK_CALL_ABORT(
+            device->createComputePipelineState(pipelineDesc, pipelineState.writeRef()));
+
+        const int numberCount = 4;
+        float initialData[] = { 0.0f, 0.0f, 0.0f, 0.0f };
+        IBufferResource::Desc bufferDesc = {};
+        bufferDesc.sizeInBytes = numberCount * sizeof(float);
+        bufferDesc.format = gfx::Format::Unknown;
+        bufferDesc.elementSize = sizeof(float);
+        bufferDesc.allowedStates = ResourceStateSet(
+            ResourceState::ShaderResource,
+            ResourceState::UnorderedAccess,
+            ResourceState::CopyDestination,
+            ResourceState::CopySource);
+        bufferDesc.defaultState = ResourceState::UnorderedAccess;
+        bufferDesc.memoryType = MemoryType::DeviceLocal;
+
+        ComPtr<IBufferResource> numbersBuffer;
+        GFX_CHECK_CALL_ABORT(device->createBufferResource(
+            bufferDesc,
+            (void*)initialData,
+            numbersBuffer.writeRef()));
+
+        ComPtr<IResourceView> bufferView;
+        IResourceView::Desc viewDesc = {};
+        viewDesc.type = IResourceView::Type::UnorderedAccess;
+        viewDesc.format = Format::Unknown;
+        GFX_CHECK_CALL_ABORT(
+            device->createBufferView(numbersBuffer, nullptr, viewDesc, bufferView.writeRef()));
+
+        // We have done all the set up work, now it is time to start recording a command buffer for
+        // GPU execution.
+        {
+            ICommandQueue::Desc queueDesc = { ICommandQueue::QueueType::Graphics };
+            auto queue = device->createCommandQueue(queueDesc);
+
+            auto commandBuffer = transientHeap->createCommandBuffer();
+            auto encoder = commandBuffer->encodeComputeCommands();
+
+            auto rootObject = encoder->bindPipeline(pipelineState);
+
+            ShaderCursor entryPointCursor(
+                rootObject->getEntryPoint(0)); // get a cursor the the first entry-point.
+            // Bind buffer view to the entry point.
+            entryPointCursor.getPath("buffer").setResource(bufferView);
+
+            encoder->dispatchCompute(1, 1, 1);
+            encoder->endEncoding();
+            commandBuffer->close();
+            queue->executeCommandBuffer(commandBuffer);
+            queue->waitOnHost();
+        }
+
+        compareComputeResult(
+            device,
+            numbersBuffer,
+            Slang::makeArray<float>(2.0));
+    }
+
+    SLANG_UNIT_TEST(linkTimeConstantD3D12)
+    {
+        runTestImpl(linkTimeConstantTestImpl, unitTestContext, Slang::RenderApiFlag::D3D12);
+    }
+
+    SLANG_UNIT_TEST(linkTimeConstantVulkan)
+    {
+        runTestImpl(linkTimeConstantTestImpl, unitTestContext, Slang::RenderApiFlag::Vulkan);
+    }
+
+}
diff --git a/tools/gfx-unit-test/link-time-constant.slang b/tools/gfx-unit-test/link-time-constant.slang
new file mode 100644
index 000000000..385932dd4
--- /dev/null
+++ b/tools/gfx-unit-test/link-time-constant.slang
@@ -0,0 +1,20 @@
+extern static const bool turnOnFeature;
+extern static const float constValue;
+
+// Main entry-point. Write some value into buffer depending on link
+// time constant.
+[shader("compute")]
+[numthreads(4, 1, 1)]
+void computeMain(
+    uint3 sv_dispatchThreadID: SV_DispatchThreadID,
+    uniform RWStructuredBuffer<float> buffer)
+{
+    if (turnOnFeature)
+    {
+        buffer[0] = constValue;
+    }
+    else
+    {
+        buffer[0] = -1.0;
+    }
+}