From c43f6fa55aca23365c86c6ec1737d42be74d9d3e Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Tue, 7 Jan 2025 22:26:31 -0800
Subject: Lower varying parameters as pointers instead of SSA values. (#5919)

* Add executable test on matrix-typed vertex input.
* Fix emit logic of matrix layout qualifier.
* Pass fragment shader varying input by constref to allow EvaluateAttributeAtCentroid etc. to be implemented correctly.
---
 source/slang/slang-emit-c-like.cpp | 40 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

(limited to 'source/slang/slang-emit-c-like.cpp')

diff --git a/source/slang/slang-emit-c-like.cpp b/source/slang/slang-emit-c-like.cpp
index 3175f1b07..64cc9969c 100644
--- a/source/slang/slang-emit-c-like.cpp
+++ b/source/slang/slang-emit-c-like.cpp
@@ -1537,6 +1537,30 @@ bool CLikeSourceEmitter::shouldFoldInstIntoUseSites(IRInst* inst)
             return true;
     }
 
+    if (auto load = as<IRLoad>(inst))
+    {
+        // Loads from a constref global param should always be folded.
+        auto ptrType = load->getPtr()->getDataType();
+        if (load->getPtr()->getOp() == kIROp_GlobalParam)
+        {
+            if (ptrType->getOp() == kIROp_ConstRefType)
+                return true;
+            if (auto ptrTypeBase = as<IRPtrTypeBase>(ptrType))
+            {
+                auto addrSpace = ptrTypeBase->getAddressSpace();
+                switch (addrSpace)
+                {
+                case Slang::AddressSpace::Uniform:
+                case Slang::AddressSpace::Input:
+                case Slang::AddressSpace::BuiltinInput:
+                    return true;
+                default:
+                    break;
+                }
+            }
+        }
+    }
+
     // Always hold if inst is a call into an [__alwaysFoldIntoUseSite] function.
     if (auto call = as<IRCall>(inst))
     {
@@ -4709,9 +4733,21 @@ void CLikeSourceEmitter::emitGlobalParam(IRGlobalParam* varDecl)
     auto rawType = varDecl->getDataType();
 
     auto varType = rawType;
-    if (auto outType = as<IROutTypeBase>(varType))
+    if (auto ptrType = as<IRPtrTypeBase>(varType))
     {
-        varType = outType->getValueType();
+        switch (ptrType->getAddressSpace())
+        {
+        case AddressSpace::Input:
+        case AddressSpace::Output:
+        case AddressSpace::BuiltinInput:
+        case AddressSpace::BuiltinOutput:
+            varType = ptrType->getValueType();
+            break;
+        default:
+            if (as<IROutTypeBase>(ptrType))
+                varType = ptrType->getValueType();
+            break;
+        }
     }
     if (as<IRVoidType>(varType))
         return;
-- 
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