Use symbol alias instead of wrapper synthesis to implement link-time types. (#8603)

This change achieves link-time type resolution with a different
mechanism.

For `extern struct Foo : IFoo = FooImpl;`,
instead of synthesizing a wrapper type `Foo` that has a `FooImpl inner`
field and dispatches all interface method calls to `inner.method()`,
this PR completely removes this synthesis step, and instead just lower
such `extern`/`export` types as `IRSymbolAlias` instructions that is
just a reference to the type being wrapped.

Then we extend the linker logic to clone the referenced symbol instead
of the SymbolAlias insts itself during linking.

By doing so, we greatly simply the logic need to support link-time
types, and achieves higher robustness by not having to deal with many
AST synthesis scenarios.

Closes #8554.

---------

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

1 files changed, 156 insertions, 0 deletions

diff --git a/tools/gfx-unit-test/link-time-type-multi-use.cpp b/tools/gfx-unit-test/link-time-type-multi-use.cpp
new file mode 100644
index 000000000..4dc6d085e
--- /dev/null
+++ b/tools/gfx-unit-test/link-time-type-multi-use.cpp
@@ -0,0 +1,156 @@
+#include "core/slang-basic.h"
+#include "core/slang-blob.h"
+#include "gfx-test-util.h"
+#include "slang-rhi.h"
+#include "slang-rhi/shader-cursor.h"
+#include "unit-test/slang-unit-test.h"
+
+using namespace rhi;
+
+// Test that a type can be used to serve multiple link-time type requirements.
+
+namespace gfx_test
+{
+static Slang::Result loadProgram(
+    rhi::IDevice* device,
+    Slang::ComPtr<rhi::IShaderProgram>& outShaderProgram,
+    slang::ProgramLayout*& slangReflection,
+    bool linkSpecialization = false)
+{
+    const char* moduleInterfaceSrc = R"(
+            interface IFoo { int getFoo(); }
+            interface IBar { int getBar(); }
+            struct SimpleImpl : IFoo, IBar
+            {
+                int getFoo() { return 10; }
+                int getBar() { return 20; }
+            }
+        )";
+    const char* module0Src = R"(
+            import ifoo;
+            extern struct Foo : IFoo;
+            extern struct Bar : IBar;
+            uniform Foo gFoo;
+            uniform Bar gBar;
+            [numthreads(1,1,1)]
+            void computeMain(uniform RWStructuredBuffer<int> buffer)
+            {
+                buffer[0] = gFoo.getFoo() + gBar.getBar();
+            }
+        )";
+    const char* module1Src = R"(
+            import ifoo;
+            export struct Foo : IFoo = SimpleImpl;
+            export struct Bar : IBar = SimpleImpl;
+        )";
+    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();
+
+    ShaderProgramDesc programDesc = {};
+    programDesc.slangGlobalScope = composedProgram.get();
+
+    auto shaderProgram = device->createShaderProgram(programDesc);
+
+    outShaderProgram = shaderProgram;
+    return SLANG_OK;
+}
+
+void linkTimeTypeMultiUseTestImpl(IDevice* device, UnitTestContext* context)
+{
+    // Create pipeline without both modules linked, specifying both Foo and Bar to be SimpleImpl.
+    ComPtr<IShaderProgram> shaderProgram;
+    slang::ProgramLayout* slangReflection;
+    GFX_CHECK_CALL_ABORT(loadProgram(device, shaderProgram, slangReflection, true));
+
+    ComputePipelineDesc pipelineDesc = {};
+    pipelineDesc.program = shaderProgram.get();
+    ComPtr<IComputePipeline> pipelineState;
+    GFX_CHECK_CALL_ABORT(device->createComputePipeline(pipelineDesc, pipelineState.writeRef()));
+
+    const int numberCount = 4;
+    float initialData[] = {0.0f, 0.0f, 0.0f, 0.0f};
+    BufferDesc bufferDesc = {};
+    bufferDesc.size = numberCount * sizeof(float);
+    bufferDesc.format = rhi::Format::Undefined;
+    bufferDesc.elementSize = sizeof(float);
+    bufferDesc.usage = BufferUsage::ShaderResource | BufferUsage::UnorderedAccess |
+                       BufferUsage::CopyDestination | BufferUsage::CopySource;
+    bufferDesc.defaultState = ResourceState::UnorderedAccess;
+    bufferDesc.memoryType = MemoryType::DeviceLocal;
+
+    ComPtr<IBuffer> numbersBuffer;
+    GFX_CHECK_CALL_ABORT(
+        device->createBuffer(bufferDesc, (void*)initialData, numbersBuffer.writeRef()));
+
+    auto queue = device->getQueue(QueueType::Graphics);
+
+    // We have done all the set up work, now it is time to start recording a command buffer for
+    // GPU execution.
+    {
+        auto commandEncoder = queue->createCommandEncoder();
+        auto computePassEncoder = commandEncoder->beginComputePass();
+
+        auto rootObject = computePassEncoder->bindPipeline(pipelineState);
+
+        ShaderCursor entryPointCursor(
+            rootObject->getEntryPoint(0)); // get a cursor the the first entry-point.
+        // Bind buffer to the entry point.
+        entryPointCursor.getPath("buffer").setBinding(Binding(numbersBuffer));
+
+        computePassEncoder->dispatchCompute(1, 1, 1);
+        computePassEncoder->end();
+        auto commandBuffer = commandEncoder->finish();
+        queue->submit(commandBuffer);
+        queue->waitOnHost();
+    }
+
+    compareComputeResult(device, numbersBuffer, std::array{30});
+}
+
+SLANG_UNIT_TEST(linkTimeTypeMultiUseD3D12)
+{
+    runTestImpl(linkTimeTypeMultiUseTestImpl, unitTestContext, DeviceType::D3D12);
+}
+
+SLANG_UNIT_TEST(linkTimeTypeMultiUseVulkan)
+{
+    runTestImpl(linkTimeTypeMultiUseTestImpl, unitTestContext, DeviceType::Vulkan);
+}
+
+} // namespace gfx_test