From d52c072777b9c9a9df9041b8b6cd199df7e43394 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Sat, 3 Apr 2010 07:21:39 +0000 Subject: [PATCH] require that the branch being controlled by the IV exits the loop. With this information we can guarantee the iteration count of the loop is bounded by the compare. I think this xforms is finally safe now. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100285 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/IndVarSimplify.cpp | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp index d32082e5dcd..6605666e45d 100644 --- a/lib/Transforms/Scalar/IndVarSimplify.cpp +++ b/lib/Transforms/Scalar/IndVarSimplify.cpp @@ -691,8 +691,15 @@ void IndVarSimplify::HandleFloatingPointIV(Loop *L, PHINode *PN) { BranchInst *TheBr = cast(Compare->use_back()); - // FIXME: Need to verify that the branch actually controls the iteration count - // of the loop. If not, the new IV can overflow and noone will notice. + // We need to verify that the branch actually controls the iteration count + // of the loop. If not, the new IV can overflow and no one will notice. + // The branch block must be in the loop and one of the successors must be out + // of the loop. + assert(TheBr->isConditional() && "Can't use fcmp if not conditional"); + if (!L->contains(TheBr->getParent()) || + (L->contains(TheBr->getSuccessor(0)) && + L->contains(TheBr->getSuccessor(1)))) + return; // If it isn't a comparison with an integer-as-fp (the exit value), we can't -- 2.34.1