[llvm-commits] [llvm] r100828 - /llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp

[Dan Gohman]

Author: djg
Date: Thu Apr  8 18:36:27 2010
New Revision: 100828

URL: http://llvm.org/viewvc/llvm-project?rev=100828&view=rev
Log:
Avoid allocating a value of zero in a register if the initial formula
inputs happen to negate each other.

Modified:
    llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp?rev=100828&r1=100827&r2=100828&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp Thu Apr  8 18:36:27 2010
@@ -262,11 +262,15 @@
   SmallVector<const SCEV *, 4> Bad;
   DoInitialMatch(S, L, Good, Bad, SE, DT);
   if (!Good.empty()) {
-    BaseRegs.push_back(SE.getAddExpr(Good));
+    const SCEV *Sum = SE.getAddExpr(Good);
+    if (!Sum->isZero())
+      BaseRegs.push_back(Sum);
     AM.HasBaseReg = true;
   }
   if (!Bad.empty()) {
-    BaseRegs.push_back(SE.getAddExpr(Bad));
+    const SCEV *Sum = SE.getAddExpr(Bad);
+    if (!Sum->isZero())
+      BaseRegs.push_back(Sum);
     AM.HasBaseReg = true;
   }
 }