From bd6306cdaa4a49344658bd026721b6532e103d09 Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Fri, 24 Feb 2023 10:01:47 -0800
Subject: More control flow simplifications. (#2673)

* More control flow and Phi param simplifications.

* Fix.

* Fix gcc error.

* Fix.

* More IR cleanup.

* Fix bug in phi param dce + ifelse simplify.

* Propagate and DCE side-effect-free functions.

* Enhance CFG simplifcation to remove loops with no side effects.

* Fix.

* Fixes.

* Fix tests. Add [__AlwaysFoldIntoUseSite] for rayPayloadLocation.

* More cleanup.

* Fixes.

* Fix.

---------

Co-authored-by: Yong He <yhe@nvidia.com>
---
 source/slang/slang-emit-cpp.cpp | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

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

diff --git a/source/slang/slang-emit-cpp.cpp b/source/slang/slang-emit-cpp.cpp
index ba6b26ec6..795ec74b0 100644
--- a/source/slang/slang-emit-cpp.cpp
+++ b/source/slang/slang-emit-cpp.cpp
@@ -1557,6 +1557,46 @@ void CPPSourceEmitter::emitGlobalInstImpl(IRInst* inst)
     }
 }
 
+bool CPPSourceEmitter::shouldFoldInstIntoUseSites(IRInst* inst)
+{
+    bool result = Super::shouldFoldInstIntoUseSites(inst);
+    if (!result)
+        return result;
+    if (as<IRVectorType>(inst->getDataType()) || as<IRMatrixType>(inst->getDataType()))
+    {
+        // If a vector value is being used in a reshape/cast,
+        // we should not fold it because the implementation of cast will have multiple references to it.
+        for (auto use = inst->firstUse; use; use = use->nextUse)
+        {
+            switch (use->getUser()->getOp())
+            {
+            case kIROp_MatrixReshape:
+            case kIROp_VectorReshape:
+            case kIROp_IntCast:
+            case kIROp_FloatCast:
+            case kIROp_CastIntToFloat:
+            case kIROp_CastFloatToInt:
+                return false;
+            default:
+                break;
+            }
+        }
+        switch (inst->getOp())
+        {
+        case kIROp_MatrixReshape:
+        case kIROp_VectorReshape:
+        case kIROp_IntCast:
+        case kIROp_FloatCast:
+        case kIROp_CastIntToFloat:
+        case kIROp_CastFloatToInt:
+            return false;
+        default:
+            break;
+        }
+    }
+    return true;
+}
+
 static bool _isExported(IRInst* inst)
 {
     for (auto decoration : inst->getDecorations())
-- 
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