X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FInstructionSimplify.cpp;h=87125191ad0e77f429e177add08af6e2148b9ce6;hb=ed58a6f96f605901adc0df3ca76499d52b2d1a1a;hp=4b6320bb46a8c5b9201ecd16b99582b930801b88;hpb=a63395a30f9227bde826749d3480046301b47332;p=oota-llvm.git

diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index 4b6320bb46a..87125191ad0 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -8,8 +8,10 @@
 //===----------------------------------------------------------------------===//
 //
 // This file implements routines for folding instructions into simpler forms
-// that do not require creating new instructions.  For example, this does
-// constant folding, and can handle identities like (X&0)->0.
+// that do not require creating new instructions.  This does constant folding
+// ("add i32 1, 1" -> "2") but can also handle non-constant operands, either
+// returning a constant ("and i32 %x, 0" -> "0") or an already existing value
+// ("and i32 %x, %x" -> "%x").
 //
 //===----------------------------------------------------------------------===//
 
@@ -296,7 +298,7 @@ static Value *SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD,
     return Op0;
 
   // A & ~A  =  ~A & A  =  0
-  Value *A, *B;
+  Value *A = 0, *B = 0;
   if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
       (match(Op1, m_Not(m_Value(A))) && A == Op0))
     return Constant::getNullValue(Op0->getType());
@@ -375,7 +377,7 @@ static Value *SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD,
     return Op1;
 
   // A | ~A  =  ~A | A  =  -1
-  Value *A, *B;
+  Value *A = 0, *B = 0;
   if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
       (match(Op1, m_Not(m_Value(A))) && A == Op0))
     return Constant::getAllOnesValue(Op0->getType());
@@ -450,7 +452,7 @@ static Value *SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD,
     return Constant::getNullValue(Op0->getType());
 
   // A ^ ~A  =  ~A ^ A  =  -1
-  Value *A, *B;
+  Value *A = 0, *B = 0;
   if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
       (match(Op1, m_Not(m_Value(A))) && A == Op0))
     return Constant::getAllOnesValue(Op0->getType());