Fix a XOR reassociation bug.

When Reassociator optimize "(x | C1)" ^ "(X & C2)", it may swap the two
subexpressions, however, it forgot to swap cached constants (of C1 and C2)
accordingly.

rdar://13739160

llvm-svn: 180676

1 files changed, 6 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index fc3b38ee53b..a3c241dc0f2 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -1195,9 +1195,6 @@ bool Reassociate::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, XorOpnd *Opnd2,
   if (X != Opnd2->getSymbolicPart())
     return false;
 
-  const APInt &C1 = Opnd1->getConstPart();
-  const APInt &C2 = Opnd2->getConstPart();
-
   // This many instruction become dead.(At least "Opnd1 ^ Opnd2" will die.)
   int DeadInstNum = 1;
   if (Opnd1->getValue()->hasOneUse())
@@ -1215,6 +1212,8 @@ bool Reassociate::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, XorOpnd *Opnd2,
     if (Opnd2->isOrExpr())
       std::swap(Opnd1, Opnd2);
 
+    const APInt &C1 = Opnd1->getConstPart();
+    const APInt &C2 = Opnd2->getConstPart();
     APInt C3((~C1) ^ C2);
 
     // Do not increase code size!
@@ -1230,6 +1229,8 @@ bool Reassociate::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, XorOpnd *Opnd2,
   } else if (Opnd1->isOrExpr()) {
     // Xor-Rule 3: (x | c1) ^ (x | c2) = (x & c3) ^ c3 where c3 = c1 ^ c2
     //
+    const APInt &C1 = Opnd1->getConstPart();
+    const APInt &C2 = Opnd2->getConstPart();
     APInt C3 = C1 ^ C2;
     
     // Do not increase code size
@@ -1244,6 +1245,8 @@ bool Reassociate::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, XorOpnd *Opnd2,
   } else {
     // Xor-Rule 4: (x & c1) ^ (x & c2) = (x & (c1^c2))
     //
+    const APInt &C1 = Opnd1->getConstPart();
+    const APInt &C2 = Opnd2->getConstPart();
     APInt C3 = C1 ^ C2;
     Res = createAndInstr(I, X, C3);
   }