Add cuda codegen bug repro

This just compiles tests/compute/simlpe.slang for PTX with the new compilation API, in
order to reproduce a code generation bug.

Author: aleino-nv

tools/slang-unit-test/unit-test-find-check-entrypoint.cpp

@@ -71,3 +71,68 @@ SLANG_UNIT_TEST(findAndCheckEntryPoint)
     SLANG_CHECK(code != nullptr);
     SLANG_CHECK(code->getBufferSize() != 0);
 }
+
+// This test reproduces issue #6507, where it was noticed that compilation of
+// tests/compute/simple.slang for PTX target generates invalid code.
+// TODO: Remove this when issue #4759 is resolved, because at that point
+// tests/compute/simple.slang should cover the same issue.
+SLANG_UNIT_TEST(cudaCodeGenBug)
+{
+    // Source for a module that contains an undecorated entrypoint.
+    const char* userSourceBody = R"(
+        RWStructuredBuffer<float> outputBuffer;
+
+        [numthreads(4, 1, 1)]
+        void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+        {
+            outputBuffer[dispatchThreadID.x] = float(dispatchThreadID.x);
+        }
+        )";
+
+    auto moduleName = "moduleG" + String(Process::getId());
+    String userSource = "import " + moduleName + ";\n" + userSourceBody;
+    ComPtr<slang::IGlobalSession> globalSession;
+    SLANG_CHECK(slang_createGlobalSession(SLANG_API_VERSION, globalSession.writeRef()) == SLANG_OK);
+    slang::TargetDesc targetDesc = {};
+    targetDesc.format = SLANG_PTX;
+    slang::SessionDesc sessionDesc = {};
+    sessionDesc.targetCount = 1;
+    sessionDesc.targets = &targetDesc;
+    ComPtr<slang::ISession> session;
+    SLANG_CHECK(globalSession->createSession(sessionDesc, session.writeRef()) == SLANG_OK);
+
+    ComPtr<slang::IBlob> diagnosticBlob;
+    auto module = session->loadModuleFromSourceString(
+        "m",
+        "m.slang",
+        userSourceBody,
+        diagnosticBlob.writeRef());
+    SLANG_CHECK(module != nullptr);
+
+    ComPtr<slang::IEntryPoint> entryPoint;
+    module->findAndCheckEntryPoint(
+        "computeMain",
+        SLANG_STAGE_COMPUTE,
+        entryPoint.writeRef(),
+        diagnosticBlob.writeRef());
+    SLANG_CHECK(entryPoint != nullptr);
+
+    ComPtr<slang::IComponentType> compositeProgram;
+    slang::IComponentType* components[] = {module, entryPoint.get()};
+    session->createCompositeComponentType(
+        components,
+        2,
+        compositeProgram.writeRef(),
+        diagnosticBlob.writeRef());
+    SLANG_CHECK(compositeProgram != nullptr);
+
+    ComPtr<slang::IComponentType> linkedProgram;
+    compositeProgram->link(linkedProgram.writeRef(), diagnosticBlob.writeRef());
+    SLANG_CHECK(linkedProgram != nullptr);
+
+    ComPtr<slang::IBlob> code;
+    auto res = linkedProgram->getEntryPointCode(0, 0, code.writeRef(), diagnosticBlob.writeRef());
+    SLANG_CHECK(res == SLANG_OK);
+    SLANG_CHECK(code != nullptr);
+    SLANG_CHECK(code->getBufferSize() != 0);
+}