commit eb4152c192ad226a1dee825f1433277e1851edbc
author Dan Gohman <gohman@apple.com> Tue Jul 20 16:53:00 2010 +0000
committer Dan Gohman <gohman@apple.com> Tue Jul 20 16:53:00 2010 +0000
tree 619be4a0052cd661fcfc1126487fd40be5773f90
parent 08993c03abed359171d12b50ab38da0ac331cfb7

Add a fast path for x - x.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108855 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/ScalarEvolution.cpp

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index f0bc936..179aa88 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -2442,6 +2442,10 @@
 ///
 const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS,
                                           const SCEV *RHS) {
+  // Fast path: X - X --> 0.
+  if (LHS == RHS)
+    return getConstant(LHS->getType(), 0);
+
   // X - Y --> X + -Y
   return getAddExpr(LHS, getNegativeSCEV(RHS));
 }