From 6e0ce24e0ca8b0dc05872b9b4cec3a18972bee40 Mon Sep 17 00:00:00 2001
From: Andrew Trick <atrick@apple.com>
Date: Thu, 30 Jun 2011 19:02:17 +0000
Subject: indvars -disable-iv-rewrite: handle cloning binary operators that
 cannot overflow.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134177 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/IndVarSimplify.cpp | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

(limited to 'lib')

diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp
index 00f8831..77642e5 100644
--- a/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -659,9 +659,11 @@ Instruction *WidenIV::CloneIVUser(Instruction *NarrowUse,
                                                     LHS, RHS,
                                                     NarrowBO->getName());
     Builder.Insert(WideBO);
-    if (NarrowBO->hasNoUnsignedWrap()) WideBO->setHasNoUnsignedWrap();
-    if (NarrowBO->hasNoSignedWrap()) WideBO->setHasNoSignedWrap();
-
+    if (const OverflowingBinaryOperator *OBO =
+        dyn_cast<OverflowingBinaryOperator>(NarrowBO)) {
+      if (OBO->hasNoUnsignedWrap()) WideBO->setHasNoUnsignedWrap();
+      if (OBO->hasNoSignedWrap()) WideBO->setHasNoSignedWrap();
+    }
     return WideBO;
   }
   llvm_unreachable(0);
@@ -1121,6 +1123,8 @@ void IndVarSimplify::SimplifyIVUsersNoRewrite(Loop *L, SCEVExpander &Rewriter) {
       while (!SimpleIVUsers.empty()) {
         Instruction *UseInst, *Operand;
         tie(UseInst, Operand) = SimpleIVUsers.pop_back_val();
+        // Bypass back edges to avoid extra work.
+        if (UseInst == CurrIV) continue;
 
         if (EliminateIVUser(UseInst, Operand)) {
           pushIVUsers(Operand, Simplified, SimpleIVUsers);
-- 
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