From c8e6a6452f4e531dca09152178bae2f9a2fb999a Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Wed, 10 May 2023 09:11:36 -0700
Subject: Generate faster derivative for div by const operations. (#2877)

* Generate faster derivative for div by const operations.

* Increase `kMaxIterationsToAttempt` to 256.

---------

Co-authored-by: Yong He <yhe@nvidia.com>
---
 source/slang/slang-ir-util.cpp | 68 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

(limited to 'source/slang/slang-ir-util.cpp')

diff --git a/source/slang/slang-ir-util.cpp b/source/slang/slang-ir-util.cpp
index 55c2b18c0..a978edc48 100644
--- a/source/slang/slang-ir-util.cpp
+++ b/source/slang/slang-ir-util.cpp
@@ -846,6 +846,74 @@ bool isGlobalOrUnknownMutableAddress(IRGlobalValueWithCode* parentFunc, IRInst*
     return (addrInstParent != parentFunc);
 }
 
+bool isZero(IRInst* inst)
+{
+    switch (inst->getOp())
+    {
+    case kIROp_IntLit:
+        return as<IRIntLit>(inst)->getValue() == 0;
+    case kIROp_FloatLit:
+        return as<IRFloatLit>(inst)->getValue() == 0.0;
+    case kIROp_BoolLit:
+        return as<IRBoolLit>(inst)->getValue() == false;
+    case kIROp_MakeVector:
+    case kIROp_MakeVectorFromScalar:
+    case kIROp_MakeMatrix:
+    case kIROp_MakeMatrixFromScalar:
+    case kIROp_MatrixReshape:
+    case kIROp_VectorReshape:
+    {
+        for (UInt i = 0; i < inst->getOperandCount(); i++)
+        {
+            if (!isZero(inst->getOperand(i)))
+            {
+                return false;
+            }
+        }
+        return true;
+    }
+    case kIROp_CastIntToFloat:
+    case kIROp_CastFloatToInt:
+        return isZero(inst->getOperand(0));
+    default:
+        return false;
+    }
+}
+
+bool isOne(IRInst* inst)
+{
+    switch (inst->getOp())
+    {
+    case kIROp_IntLit:
+        return as<IRIntLit>(inst)->getValue() == 1;
+    case kIROp_FloatLit:
+        return as<IRFloatLit>(inst)->getValue() == 1.0;
+    case kIROp_BoolLit:
+        return as<IRBoolLit>(inst)->getValue();
+    case kIROp_MakeVector:
+    case kIROp_MakeVectorFromScalar:
+    case kIROp_MakeMatrix:
+    case kIROp_MakeMatrixFromScalar:
+    case kIROp_MatrixReshape:
+    case kIROp_VectorReshape:
+    {
+        for (UInt i = 0; i < inst->getOperandCount(); i++)
+        {
+            if (!isOne(inst->getOperand(i)))
+            {
+                return false;
+            }
+        }
+        return true;
+    }
+    case kIROp_CastIntToFloat:
+    case kIROp_CastFloatToInt:
+        return isOne(inst->getOperand(0));
+    default:
+        return false;
+    }
+}
+
 struct GenericChildrenMigrationContextImpl
 {
     IRCloneEnv cloneEnv;
-- 
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