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don't call MergeBasicBlockIntoOnlyPred on a block whose only

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predecessor is itself.  This doesn't make sense, and this is
a dead infinite loop anyway.

llvm-svn: 60210
This commit is contained in:
Chris Lattner 2008-11-28 19:54:49 +00:00
parent 850748f5de
commit a854ab3760
3 changed files with 30 additions and 10 deletions
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20
lib/Transforms/Scalar/CodeGenPrepare.cpp
View File

@ -205,16 +205,18 @@ void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) {
// If the destination block has a single pred, then this is a trivial edge,
// just collapse it.
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 (SinglePred != DestBB) {
// 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;
if (isEntry && BB != &BB->getParent()->getEntryBlock())
BB->moveBefore(&BB->getParent()->getEntryBlock());
DOUT << "AFTER:\n" << *DestBB << "\n\n\n";
return;
}
}
// Otherwise, we have multiple predecessors of BB. Update the PHIs in DestBB

3
lib/Transforms/Scalar/JumpThreading.cpp
View File

@ -164,7 +164,8 @@ bool JumpThreading::ProcessBlock(BasicBlock *BB) {
// because now the condition in this block can be threaded through
// predecessors of our predecessor block.
if (BasicBlock *SinglePred = BB->getSinglePredecessor())
if (SinglePred->getTerminator()->getNumSuccessors() == 1) {
if (SinglePred->getTerminator()->getNumSuccessors() == 1 &&
SinglePred != BB) {
// 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();

17
test/Transforms/JumpThreading/2008-11-28-InfLoop.ll Normal file
View File

@ -0,0 +1,17 @@
; RUN: llvm-as < %s | opt -jump-threading | llvm-dis
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target triple = "i386-apple-darwin9.5"
%struct.decContext = type { i32 }
%struct.decNumber = type { i32, i32 }
define i32 @decNumberPower(%struct.decNumber* %res, %struct.decNumber* %lhs, %struct.decNumber* %rhs, %struct.decContext* %set) nounwind {
entry:
br i1 true, label %decDivideOp.exit, label %bb7.i
bb7.i: ; preds = %bb7.i, %entry
br label %bb7.i
decDivideOp.exit: ; preds = %entry
ret i32 undef
}