From 6f2ce72b038b34e84819ddfc5d658166ed879eaa Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Thu, 27 Feb 2025 16:57:52 -0800
Subject: Map `SV_InstanceID` to `gl_InstanceIndex-gl_BaseInstance` (#6468)

* Map `SV_InstanceID` to `gl_InstanceIndex-gl_BaseInstance`

* Fix ci.
---
 source/slang/slang-emit-c-like.cpp | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

(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 db2c0150f..946e9c429 100644
--- a/source/slang/slang-emit-c-like.cpp
+++ b/source/slang/slang-emit-c-like.cpp
@@ -345,6 +345,20 @@ IRNumThreadsDecoration* CLikeSourceEmitter::getComputeThreadGroupSize(
     return decor;
 }
 
+String CLikeSourceEmitter::getTargetBuiltinVarName(IRInst* inst, IRTargetBuiltinVarName builtinName)
+{
+    switch (builtinName)
+    {
+    case IRTargetBuiltinVarName::SpvInstanceIndex:
+        return "gl_InstanceIndex";
+    case IRTargetBuiltinVarName::SpvBaseInstance:
+        return "gl_BaseInstance";
+    }
+    if (auto linkage = inst->findDecoration<IRLinkageDecoration>())
+        return linkage->getMangledName();
+    return generateName(inst);
+}
+
 List<IRWitnessTableEntry*> CLikeSourceEmitter::getSortedWitnessTableEntries(
     IRWitnessTable* witnessTable)
 {
@@ -1208,6 +1222,11 @@ String CLikeSourceEmitter::generateName(IRInst* inst)
         return externCppDecoration->getName();
     }
 
+    if (auto builtinTargetVarDecoration = inst->findDecoration<IRTargetBuiltinVarDecoration>())
+    {
+        return getTargetBuiltinVarName(inst, builtinTargetVarDecoration->getBuiltinVarName());
+    }
+
     // If we have a name hint on the instruction, then we will try to use that
     // to provide the basis for the actual name in the output code.
     if (auto nameHintDecoration = inst->findDecoration<IRNameHintDecoration>())
-- 
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