[ScalarEvolution] Fix base condition in isNormalAddRecPHI.

Summary:
The function is meant to recurse until it comes upon the
phi it's looking for. However, with the current condition,
it will recurse until it finds anything _but_ the phi.

The function will even fail for simple cases like:
  %i = phi i32 [ %inc, %loop ], ...
  ...
  %inc = add i32 %i, 1

because the base condition will not happen when the phi
is recursed to, and the recursion will end with a 'false'
result since the previous instruction is a phi.

Reviewers: sanjoy, atrick

Reviewed By: sanjoy

Subscribers: Ka-Ka, bjope, llvm-commits

Committing on behalf of: Bevin Hansson (bevinh)

Differential Revision: https://reviews.llvm.org/D40946

llvm-svn: 320700

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/ScalarEvolutionExpander.cpp b/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
index b2bdb5538e5..0caff18264d 100644
--- a/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -878,7 +878,7 @@ bool SCEVExpander::isNormalAddRecExprPHI(PHINode *PN, Instruction *IncV,
   if (IncV->mayHaveSideEffects())
     return false;
 
-  if (IncV != PN)
+  if (IncV == PN)
     return true;
 
   return isNormalAddRecExprPHI(PN, IncV, L);