From 3d86d242c69a26ba2e6102f32b00b04884c4c9b1 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Thu, 27 Nov 2008 19:25:19 +0000 Subject: [PATCH] Fix PR3138: if we merge the entry block into another block, make sure to move the other block back up into the entry position! git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60179 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/JumpThreading.cpp | 6 ++++++ .../JumpThreading/2008-11-27-EntryMunge.ll | 13 +++++++++++++ 2 files changed, 19 insertions(+) create mode 100644 test/Transforms/JumpThreading/2008-11-27-EntryMunge.ll diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp index ec35a891e05..5de5fb3b776 100644 --- a/lib/Transforms/Scalar/JumpThreading.cpp +++ b/lib/Transforms/Scalar/JumpThreading.cpp @@ -165,7 +165,13 @@ bool JumpThreading::ProcessBlock(BasicBlock *BB) { // predecessors of our predecessor block. if (BasicBlock *SinglePred = BB->getSinglePredecessor()) if (SinglePred->getTerminator()->getNumSuccessors() == 1) { + // 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(BB); + + if (isEntry && BB != &BB->getParent()->getEntryBlock()) + BB->moveBefore(&BB->getParent()->getEntryBlock()); return true; } diff --git a/test/Transforms/JumpThreading/2008-11-27-EntryMunge.ll b/test/Transforms/JumpThreading/2008-11-27-EntryMunge.ll new file mode 100644 index 00000000000..216dacb8d26 --- /dev/null +++ b/test/Transforms/JumpThreading/2008-11-27-EntryMunge.ll @@ -0,0 +1,13 @@ +; RUN: llvm-as < %s | opt -jump-threading -simplifycfg | llvm-dis | grep {ret i32 0} +; PR3138 + +define i32 @jt() { +entry: + br i1 true, label %bb3, label %bb + +bb: ; preds = %entry + unreachable + +bb3: ; preds = %entry + ret i32 0 +} -- 2.34.1