Disallow only resources in constant buffers in parameterblocks on metal (#6342)

* Neaten metal parameter block checking

* Disallow only resources in constant buffers in parameterblocks on metal

closes https://github.com/shader-slang/slang/issues/6200

* add unit test for metal parameterblock cbuffer

---------

Co-authored-by: Yong He <yonghe@outlook.com>

1 files changed, 133 insertions, 0 deletions

diff --git a/tools/slang-unit-test/unit-test-metal-parameter-block-constant-buffer.cpp b/tools/slang-unit-test/unit-test-metal-parameter-block-constant-buffer.cpp
new file mode 100644
index 000000000..d04cea974
--- /dev/null
+++ b/tools/slang-unit-test/unit-test-metal-parameter-block-constant-buffer.cpp
@@ -0,0 +1,133 @@
+// unit-test-ptr-layout.cpp
+
+#include "slang-com-ptr.h"
+#include "slang.h"
+#include "unit-test/slang-unit-test.h"
+
+#include <stdlib.h>
+
+using namespace Slang;
+
+SLANG_UNIT_TEST(metalConstantBufferInParameterBlockLayout)
+{
+    const char* testSource = R"(
+        struct T 
+        {
+            float4 m0;
+            float m1;
+            float3 m2;
+        };
+
+        ParameterBlock<ConstantBuffer<T>> params;
+    )";
+
+    ComPtr<slang::IGlobalSession> globalSession;
+    SLANG_CHECK(slang_createGlobalSession(SLANG_API_VERSION, globalSession.writeRef()) == SLANG_OK);
+
+    slang::TargetDesc targetDesc = {};
+    targetDesc.format = SLANG_METAL;
+    targetDesc.profile = globalSession->findProfile("metal");
+
+    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(
+        "test",
+        "test.slang",
+        testSource,
+        diagnosticBlob.writeRef());
+    SLANG_CHECK(module != nullptr);
+
+    auto testBody = [&]()
+    {
+        auto reflection = module->getLayout();
+
+        // Collect our layouts
+        auto paramBlockType = reflection->findTypeByName("ParameterBlock<ConstantBuffer<T>>");
+        SLANG_CHECK(paramBlockType != nullptr);
+        auto paramBlockLayout = reflection->getTypeLayout(paramBlockType);
+        SLANG_CHECK(paramBlockLayout != nullptr);
+        auto cbufferLayout = paramBlockLayout->getElementTypeLayout();
+        SLANG_CHECK(cbufferLayout != nullptr);
+        auto structLayout = cbufferLayout->getElementTypeLayout();
+        SLANG_CHECK(structLayout != nullptr);
+
+        // Check offsets follow constant buffer rules (uniform alignment)
+        // m0 : float4 should be at offset 0
+        // m1 : float  should be at offset 16 (after float4)
+        // m2 : float3 should be at offset 32 (aligned to 16-byte boundary)
+        SLANG_CHECK(structLayout->getFieldCount() == 3);
+        SLANG_CHECK(structLayout->getFieldByIndex(0)->getOffset() == 0);
+        SLANG_CHECK(structLayout->getFieldByIndex(1)->getOffset() == 16);
+        SLANG_CHECK(structLayout->getFieldByIndex(2)->getOffset() == 32);
+    };
+
+    testBody();
+}
+
+SLANG_UNIT_TEST(metalArgumentBufferLayout)
+{
+    const char* testSource = R"(
+        struct T 
+        {
+            float4 m0;
+            float m1;
+            float3 m2;
+        };
+
+        // Using ParameterBlock directly without ConstantBuffer wrapper
+        ParameterBlock<T> params;
+    )";
+
+    ComPtr<slang::IGlobalSession> globalSession;
+    SLANG_CHECK(slang_createGlobalSession(SLANG_API_VERSION, globalSession.writeRef()) == SLANG_OK);
+
+    slang::TargetDesc targetDesc = {};
+    targetDesc.format = SLANG_METAL;
+    targetDesc.profile = globalSession->findProfile("metal");
+
+    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(
+        "test",
+        "test.slang",
+        testSource,
+        diagnosticBlob.writeRef());
+    SLANG_CHECK(module != nullptr);
+
+    auto testBody = [&]()
+    {
+        auto reflection = module->getLayout();
+
+        // Collect our layouts
+        auto paramBlockType = reflection->findTypeByName("ParameterBlock<T>");
+        SLANG_CHECK(paramBlockType != nullptr);
+        auto paramBlockLayout = reflection->getTypeLayout(paramBlockType);
+        SLANG_CHECK(paramBlockLayout != nullptr);
+        auto structLayout = paramBlockLayout->getElementTypeLayout();
+        SLANG_CHECK(structLayout != nullptr);
+
+        // Check that offsets follow Metal argument buffer rules
+        // Fields should have 0 offset and meaningful binding indices
+        SLANG_CHECK(structLayout->getFieldCount() == 3);
+        SLANG_CHECK(structLayout->getFieldByIndex(0)->getOffset() == 0);
+        SLANG_CHECK(structLayout->getFieldByIndex(1)->getOffset() == 0);
+        SLANG_CHECK(structLayout->getFieldByIndex(2)->getOffset() == 0);
+        SLANG_CHECK(structLayout->getFieldByIndex(0)->getBindingIndex() == 0);
+        SLANG_CHECK(structLayout->getFieldByIndex(1)->getBindingIndex() == 1);
+        SLANG_CHECK(structLayout->getFieldByIndex(2)->getBindingIndex() == 2);
+    };
+
+    testBody();
+}