From: Chris Lattner <sabre@nondot.org>
Date: Fri, 5 Jan 2007 02:17:46 +0000 (+0000)
Subject: Compile X + ~X to -1.  This implements Instcombine/add.ll:test34
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=e617c9ed5dd374b05c312e411857c74e9b458aa0;p=oota-llvm.git

Compile X + ~X to -1.  This implements Instcombine/add.ll:test34


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@32890 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 925db6837cf..aba50dca3e7 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -1871,10 +1871,16 @@ FoundSExt:
   if (dyn_castFoldableMul(RHS, C2) == LHS)
     return BinaryOperator::createMul(LHS, AddOne(C2));
 
+  // X + ~X --> -1   since   ~X = -X-1
+  if (dyn_castNotVal(LHS) == RHS ||
+      dyn_castNotVal(RHS) == LHS)
+    return ReplaceInstUsesWith(I, ConstantInt::getAllOnesValue(I.getType()));
+  
 
   // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
   if (match(RHS, m_And(m_Value(), m_ConstantInt(C2))))
-    if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
+    if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2)))
+      return R;
 
   if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
     Value *X = 0;