From d3ed08ec3073c3cb9ac24fa3670784dd6e97a164 Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Wed, 24 Apr 2024 16:23:35 -0700
Subject: Parameter layout and reflection for Metal bindings. (#4022)

---
 source/slang/slang-legalize-types.cpp | 41 ++++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 15 deletions(-)

(limited to 'source/slang/slang-legalize-types.cpp')

diff --git a/source/slang/slang-legalize-types.cpp b/source/slang/slang-legalize-types.cpp
index fc0947c62..393b34e68 100644
--- a/source/slang/slang-legalize-types.cpp
+++ b/source/slang/slang-legalize-types.cpp
@@ -1156,23 +1156,34 @@ LegalType legalizeTypeImpl(
         auto originalElementType = uniformBufferType->getElementType();
 
         // Legalize the element type to see what we are working with.
-        auto legalElementType = legalizeType(context,
-            originalElementType);
-
-        // As a bit of a corner case, if the user requested something
-        // like `ConstantBuffer<Texture2D>` the element type would
-        // legalize to a "simple" type, and that would be interpreted
-        // as an *ordinary* type, but we really need to notice the
-        // case when the element type is simple, but *special*.
-        //
-        if( context->isSpecialType(originalElementType) )
+        LegalType legalElementType;
+        
+        if (isMetalTarget(context->targetProgram->getTargetReq()) &&
+            as<IRParameterBlockType>(uniformBufferType))
+        {
+            // On Metal, we do not need to legalize the element type of
+            // a parameter block because we can translate it directly into
+            // an argument buffer.
+            legalElementType = LegalType::simple(originalElementType);
+        }
+        else
         {
-            // Anything that has a special element type needs to
-            // be handled by the pass-specific logic in the context.
+            legalElementType = legalizeType(context, originalElementType);
+            // As a bit of a corner case, if the user requested something
+            // like `ConstantBuffer<Texture2D>` the element type would
+            // legalize to a "simple" type, and that would be interpreted
+            // as an *ordinary* type, but we really need to notice the
+            // case when the element type is simple, but *special*.
             //
-            return context->createLegalUniformBufferType(
-                uniformBufferType->getOp(),
-                legalElementType);
+            if( context->isSpecialType(originalElementType) )
+            {
+                // Anything that has a special element type needs to
+                // be handled by the pass-specific logic in the context.
+                //
+                return context->createLegalUniformBufferType(
+                    uniformBufferType->getOp(),
+                    legalElementType);
+            }
         }
 
         // Note that even when legalElementType.flavor == Simple
-- 
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