Allow default values for `extern` symbols. (#3632)

* Allow default values for `extern` symbols.

* Fix.

* Fix test.

1 files changed, 237 insertions, 0 deletions

diff --git a/tools/gfx-unit-test/link-time-default.cpp b/tools/gfx-unit-test/link-time-default.cpp
new file mode 100644
index 000000000..be9198b82
--- /dev/null
+++ b/tools/gfx-unit-test/link-time-default.cpp
@@ -0,0 +1,237 @@
+#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,
+        slang::ProgramLayout*& slangReflection,
+        bool linkSpecialization = false)
+    {
+        const char* moduleInterfaceSrc = R"(
+            interface IFoo
+            {
+                static const int offset;
+                [mutating] void setValue(float v);
+                float getValue();
+                property float val2{get;set;}
+            }
+            struct FooImpl : IFoo
+            {
+                float val;
+                static const int offset = -1;
+                [mutating] void setValue(float v) { val = v; }
+                float getValue() { return val + 1.0; }
+                property float val2 {
+                    get { return val + 2.0; }
+                    set { val = newValue; }
+                }
+            };
+            struct BarImpl : IFoo
+            {
+                float val;
+                static const int offset = 2;
+                [mutating] void setValue(float v) { val = v; }
+                float getValue() { return val + 1.0; }
+                property float val2 {
+                    get { return val; }
+                    set { val = newValue; }
+                }
+            };
+        )";
+        const char* module0Src = R"(
+            import ifoo;
+            extern struct Foo : IFoo = FooImpl;
+            extern static const float c = 0.0;
+            [numthreads(1,1,1)]
+            void computeMain(uniform RWStructuredBuffer<float> buffer)
+            {
+                Foo foo;
+                foo.setValue(3.0);
+                buffer[0] = foo.getValue() + foo.val2 + Foo.offset + c;
+            }
+        )";
+        const char* module1Src = R"(
+            import ifoo;
+            export struct Foo : IFoo = BarImpl;
+            export static const float c = 1.0;
+        )";
+        Slang::ComPtr<slang::ISession> slangSession;
+        SLANG_RETURN_ON_FAIL(device->getSlangSession(slangSession.writeRef()));
+        Slang::ComPtr<slang::IBlob> diagnosticsBlob;
+        auto moduleInterfaceBlob = Slang::UnownedRawBlob::create(moduleInterfaceSrc, strlen(moduleInterfaceSrc));
+        auto module0Blob = Slang::UnownedRawBlob::create(module0Src, strlen(module0Src));
+        auto module1Blob = Slang::UnownedRawBlob::create(module1Src, strlen(module1Src));
+        slang::IModule* moduleInterface = slangSession->loadModuleFromSource("ifoo", "ifoo.slang",
+            moduleInterfaceBlob);
+        slang::IModule* module0 = slangSession->loadModuleFromSource("module0", "path0",
+            module0Blob);
+        slang::IModule* module1 = slangSession->loadModuleFromSource("module1", "path1",
+            module1Blob);
+        ComPtr<slang::IEntryPoint> computeEntryPoint;
+        SLANG_RETURN_ON_FAIL(
+            module0->findEntryPointByName("computeMain", computeEntryPoint.writeRef()));
+
+        Slang::List<slang::IComponentType*> componentTypes;
+        componentTypes.add(moduleInterface);
+        componentTypes.add(module0);
+        if (linkSpecialization)
+            componentTypes.add(module1);
+        componentTypes.add(computeEntryPoint);
+
+        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 linkTimeDefaultTestImpl(IDevice* device, UnitTestContext* context)
+    {
+        Slang::ComPtr<ITransientResourceHeap> transientHeap;
+        ITransientResourceHeap::Desc transientHeapDesc = {};
+        transientHeapDesc.constantBufferSize = 4096;
+        GFX_CHECK_CALL_ABORT(
+            device->createTransientResourceHeap(transientHeapDesc, transientHeap.writeRef()));
+
+        // Create pipeline without linking a specialization override module, so we should
+        // see the default value of `extern Foo`.
+        ComPtr<IShaderProgram> shaderProgram;
+        slang::ProgramLayout* slangReflection;
+        GFX_CHECK_CALL_ABORT(loadProgram(device, shaderProgram, slangReflection, false));
+
+        ComputePipelineStateDesc pipelineDesc = {};
+        pipelineDesc.program = shaderProgram.get();
+        ComPtr<gfx::IPipelineState> pipelineState;
+        GFX_CHECK_CALL_ABORT(
+            device->createComputePipelineState(pipelineDesc, pipelineState.writeRef()));
+
+        // Create pipeline with a specialization override module linked in, so we should
+        // see the result of using `Bar` for `extern Foo`.
+        ComPtr<IShaderProgram> shaderProgram1;
+        GFX_CHECK_CALL_ABORT(loadProgram(device, shaderProgram1, slangReflection, true));
+
+        ComputePipelineStateDesc pipelineDesc1 = {};
+        pipelineDesc1.program = shaderProgram1.get();
+        ComPtr<gfx::IPipelineState> pipelineState1;
+        GFX_CHECK_CALL_ABORT(
+            device->createComputePipelineState(pipelineDesc1, pipelineState1.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()));
+
+        ICommandQueue::Desc queueDesc = { ICommandQueue::QueueType::Graphics };
+        auto queue = device->createCommandQueue(queueDesc);
+
+        // We have done all the set up work, now it is time to start recording a command buffer for
+        // GPU execution.
+        {
+            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>(8.0));
+
+        // Now run again with the overrided program.
+        {
+            auto commandBuffer = transientHeap->createCommandBuffer();
+            auto encoder = commandBuffer->encodeComputeCommands();
+
+            auto rootObject = encoder->bindPipeline(pipelineState1);
+
+            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>(10.0));
+    }
+
+    SLANG_UNIT_TEST(linkTimeDefaultD3D12)
+    {
+        runTestImpl(linkTimeDefaultTestImpl, unitTestContext, Slang::RenderApiFlag::D3D12);
+    }
+
+    SLANG_UNIT_TEST(linkTimeDefaultVulkan)
+    {
+        runTestImpl(linkTimeDefaultTestImpl, unitTestContext, Slang::RenderApiFlag::Vulkan);
+    }
+
+}