From e6fe67b2fb48b1f0f3c1ac8c1ce01e67c1f0bb1d Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Sun, 27 Sep 2009 15:37:03 +0000
Subject: [PATCH] Tell ScalarEvolution to forget everything it knows about a
loop before rotating the loop, since loop rotation is a very significant
change.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82901 91177308-0d34-0410-b5e6-96231b3b80d8
---
lib/Transforms/Scalar/LoopRotation.cpp | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/lib/Transforms/Scalar/LoopRotation.cpp b/lib/Transforms/Scalar/LoopRotation.cpp
index 34ba48c6b05..70c69bb1dae 100644
--- a/lib/Transforms/Scalar/LoopRotation.cpp
+++ b/lib/Transforms/Scalar/LoopRotation.cpp
@@ -177,6 +177,11 @@ bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
// Now, this loop is suitable for rotation.
+ // Anything ScalarEvolution may know about this loop or the PHI nodes
+ // in its header will soon be invalidated.
+ if (ScalarEvolution *SE = getAnalysisIfAvailable<ScalarEvolution>())
+ SE->forgetLoopBackedgeTakenCount(L);
+
// Find new Loop header. NewHeader is a Header's one and only successor
// that is inside loop. Header's other successor is outside the
// loop. Otherwise loop is not suitable for rotation.