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Fix PR3138: if we merge the entry block into another block, make sure to

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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
This commit is contained in:
Chris Lattner
2008-11-27 19:25:19 +00:00
parent a89d102b32
commit 3d86d242c6
2 changed files with 19 additions and 0 deletions
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6
lib/Transforms/Scalar/JumpThreading.cpp
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@@ -165,7 +165,13 @@ bool JumpThreading::ProcessBlock(BasicBlock *BB) {
// predecessors of our predecessor block. // predecessors of our predecessor block.
if (BasicBlock *SinglePred = BB->getSinglePredecessor()) if (BasicBlock *SinglePred = BB->getSinglePredecessor())
if (SinglePred->getTerminator()->getNumSuccessors() == 1) { 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); MergeBasicBlockIntoOnlyPred(BB);
if (isEntry && BB != &BB->getParent()->getEntryBlock())
BB->moveBefore(&BB->getParent()->getEntryBlock());
return true; return true;
} }

13
test/Transforms/JumpThreading/2008-11-27-EntryMunge.ll Normal file
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@@ -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
}