Fix Conditioanl<T, false> fields with a semantic. (#7855)

* Fix Conditioanl<T, false> fields with a semantic.

* Add unit test.

* Fix test.

1 files changed, 146 insertions, 0 deletions

diff --git a/tools/slang-unit-test/unit-test-conditional-vertex-input.cpp b/tools/slang-unit-test/unit-test-conditional-vertex-input.cpp
new file mode 100644
index 000000000..d52369152
--- /dev/null
+++ b/tools/slang-unit-test/unit-test-conditional-vertex-input.cpp
@@ -0,0 +1,146 @@
+// unit-test-unit-test-conditional-vertex-input.cpp
+
+#include "../../source/core/slang-io.h"
+#include "../../source/core/slang-process.h"
+#include "slang-com-ptr.h"
+#include "slang.h"
+#include "unit-test/slang-unit-test.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+
+using namespace Slang;
+
+// Test the compilation API for compiling an entrypoint that uses `Conditional<T>` to
+// represent conditional vertex attribute input that can be specialized away.
+
+SLANG_UNIT_TEST(conditionalVertexInput)
+{
+    const char* userSourceBody = R"(
+            struct Vertex<bool hasColor> {
+                float3 pos : POSITION;
+                Conditional<float3, hasColor> color : COLOR;
+                float3 normal : NORMAL;
+            }
+
+            extern static const bool vertexHasColor = true;
+
+            [shader("vertex")]
+            float4 vertMain(Vertex<vertexHasColor> o) {
+                if (let color = o.color.get())
+                {
+                    // If `vertexHasColor` is true, we can use `color`.
+                    return float4(o.pos + color + o.normal, 1);
+                }
+                return float4(o.pos + o.normal, 1);
+            }
+        )";
+    const char* userSourceBodyNoColor = R"(export static const bool vertexHasColor = false;)";
+
+    ComPtr<slang::IGlobalSession> globalSession;
+    SLANG_CHECK(slang_createGlobalSession(SLANG_API_VERSION, globalSession.writeRef()) == SLANG_OK);
+    slang::TargetDesc targetDesc = {};
+    targetDesc.format = SLANG_GLSL;
+    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(
+        "vertMain",
+        SLANG_STAGE_VERTEX,
+        entryPoint.writeRef(),
+        diagnosticBlob.writeRef());
+
+    // Check the program with `vertexHasColor = true`.
+    {
+        slang::IComponentType* componentTypes[2] = {module, entryPoint.get()};
+        ComPtr<slang::IComponentType> composedProgram;
+        session->createCompositeComponentType(
+            componentTypes,
+            2,
+            composedProgram.writeRef(),
+            diagnosticBlob.writeRef());
+
+        ComPtr<slang::IComponentType> linkedProgram;
+        composedProgram->link(linkedProgram.writeRef(), diagnosticBlob.writeRef());
+
+        auto paramLayout = linkedProgram->getLayout()
+                               ->getEntryPointByIndex(0)
+                               ->getParameterByIndex(0)
+                               ->getTypeLayout();
+
+        // Total number of varying inputs should be 3. (pos, color and normal)
+        SLANG_CHECK(paramLayout->getSize(slang::ParameterCategory::VaryingInput) == 3);
+
+        // Offset of `normal` should be 2.
+        SLANG_CHECK(
+            paramLayout
+                ->getFieldByIndex(2) // `o.normal`
+                ->getOffset(slang::ParameterCategory::VaryingInput) == 2);
+        ComPtr<slang::IBlob> code;
+        SLANG_CHECK(
+            linkedProgram->getEntryPointCode(0, 0, code.writeRef(), diagnosticBlob.writeRef()) ==
+            SLANG_OK);
+        auto codeStr = Slang::UnownedStringSlice((const char*)code->getBufferPointer());
+        SLANG_CHECK(codeStr.indexOf(toSlice("layout(location = 0)")) != -1);
+        SLANG_CHECK(codeStr.indexOf(toSlice("layout(location = 1)")) != -1);
+        SLANG_CHECK(codeStr.indexOf(toSlice("layout(location = 2)")) != -1);
+    }
+
+    // Check the program with `vertexHashColor = false`.
+    {
+        auto configModule = session->loadModuleFromSourceString(
+            "config",
+            "config.slang",
+            userSourceBodyNoColor,
+            diagnosticBlob.writeRef());
+        SLANG_CHECK(module != nullptr);
+
+        slang::IComponentType* componentTypes[3] = {module, entryPoint.get(), configModule};
+        ComPtr<slang::IComponentType> composedProgram;
+        session->createCompositeComponentType(
+            componentTypes,
+            3,
+            composedProgram.writeRef(),
+            diagnosticBlob.writeRef());
+
+        ComPtr<slang::IComponentType> linkedProgram;
+        composedProgram->link(linkedProgram.writeRef(), diagnosticBlob.writeRef());
+
+        auto paramLayout = linkedProgram->getLayout()
+                               ->getEntryPointByIndex(0)
+                               ->getParameterByIndex(0)
+                               ->getTypeLayout();
+
+        // Total number of varying inputs should be 2. (pos and normal)
+        SLANG_CHECK(paramLayout->getSize(slang::ParameterCategory::VaryingInput) == 2);
+
+        // Offset of `normal` should be 1.
+        SLANG_CHECK(
+            paramLayout
+                ->getFieldByIndex(2) // `o.normal`
+                ->getOffset(slang::ParameterCategory::VaryingInput) == 1);
+        ComPtr<slang::IBlob> code;
+        SLANG_CHECK(
+            linkedProgram->getEntryPointCode(0, 0, code.writeRef(), diagnosticBlob.writeRef()) ==
+            SLANG_OK);
+
+        auto codeStr = Slang::UnownedStringSlice((const char*)code->getBufferPointer());
+
+        SLANG_CHECK(codeStr.indexOf(toSlice("layout(location = 0)")) != -1);
+        SLANG_CHECK(codeStr.indexOf(toSlice("layout(location = 1)")) != -1);
+        // Resulting code should not contain `layout(location = 1)` since `color` is not used.
+        SLANG_CHECK(codeStr.indexOf(toSlice("layout(location = 2)")) == -1);
+    }
+}