From 9918fb5631974f2201a640384b7ebe672c749e43 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Thu, 27 Nov 2008 19:29:14 +0000 Subject: [PATCH] defensive patch: if CGP is merging a block with the entry block, make sure it ends up being the entry block. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60180 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/CodeGenPrepare.cpp | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/lib/Transforms/Scalar/CodeGenPrepare.cpp b/lib/Transforms/Scalar/CodeGenPrepare.cpp index caf60c8c7af..9bf39911b6c 100644 --- a/lib/Transforms/Scalar/CodeGenPrepare.cpp +++ b/lib/Transforms/Scalar/CodeGenPrepare.cpp @@ -204,8 +204,15 @@ void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) { // If the destination block has a single pred, then this is a trivial edge, // just collapse it. - if (DestBB->getSinglePredecessor()) { + if (BasicBlock *SinglePred = DestBB->getSinglePredecessor()) { + // Remember if SinglePred was the entry block of the function. If so, we + // will need to move BB back to the entry position. + bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock(); MergeBasicBlockIntoOnlyPred(DestBB); + + if (isEntry && BB != &BB->getParent()->getEntryBlock()) + BB->moveBefore(&BB->getParent()->getEntryBlock()); + DOUT << "AFTER:\n" << *DestBB << "\n\n\n"; return; }