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update the comment above llvm::SplitCriticalEdge, and make 

it abort on IndirectBrInst as describe in the comment.

llvm-svn: 85688
This commit is contained in:
Chris Lattner 2009-10-31 21:51:10 +00:00
parent 8fe6fd702d
commit ba364b0a9a
2 changed files with 30 additions and 9 deletions
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12
llvm/include/llvm/Transforms/Utils/BasicBlockUtils.h
View File

@ -116,8 +116,8 @@ bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum,
/// SplitCriticalEdge - If this edge is a critical edge, insert a new node to
/// split the critical edge. This will update DominatorTree and
/// DominatorFrontier information if it is available, thus calling this pass
/// will not invalidate either of them. This returns true if the edge was split,
/// false otherwise.
/// will not invalidate either of them. This returns the new block if the edge
/// was split, null otherwise.
///
/// If MergeIdenticalEdges is true (not the default), *all* edges from TI to the
/// specified successor will be merged into the same critical edge block.
@ -126,10 +126,16 @@ bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum,
/// dest go to one block instead of each going to a different block, but isn't
/// the standard definition of a "critical edge".
///
/// It is invalid to call this function on a critical edge that starts at an
/// IndirectBrInst. Splitting these edges will almost always create an invalid
/// program because the addr of the new block won't be the one that is jumped
/// to.
///
BasicBlock *SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
Pass *P = 0, bool MergeIdenticalEdges = false);
inline BasicBlock *SplitCriticalEdge(BasicBlock *BB, succ_iterator SI, Pass *P = 0) {
inline BasicBlock *SplitCriticalEdge(BasicBlock *BB, succ_iterator SI,
Pass *P = 0) {
return SplitCriticalEdge(BB->getTerminator(), SI.getSuccessorIndex(), P);
}

27
llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp
View File

@ -69,7 +69,7 @@ bool BreakCriticalEdges::runOnFunction(Function &F) {
bool Changed = false;
for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
TerminatorInst *TI = I->getTerminator();
if (TI->getNumSuccessors() > 1)
if (TI->getNumSuccessors() > 1 && !isa<IndirectBrInst>(TI))
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
if (SplitCriticalEdge(TI, i, this)) {
++NumBroken;
@ -150,14 +150,29 @@ static void CreatePHIsForSplitLoopExit(SmallVectorImpl<BasicBlock *> &Preds,
/// SplitCriticalEdge - If this edge is a critical edge, insert a new node to
/// split the critical edge. This will update DominatorTree and
/// DominatorFrontier information if it is available, thus calling this pass
/// will not invalidate any of them. This returns true if the edge was split,
/// false otherwise. This ensures that all edges to that dest go to one block
/// instead of each going to a different block.
//
/// DominatorFrontier information if it is available, thus calling this pass
/// will not invalidate either of them. This returns the new block if the edge
/// was split, null otherwise.
///
/// If MergeIdenticalEdges is true (not the default), *all* edges from TI to the
/// specified successor will be merged into the same critical edge block.
/// This is most commonly interesting with switch instructions, which may
/// have many edges to any one destination. This ensures that all edges to that
/// dest go to one block instead of each going to a different block, but isn't
/// the standard definition of a "critical edge".
///
/// It is invalid to call this function on a critical edge that starts at an
/// IndirectBrInst. Splitting these edges will almost always create an invalid
/// program because the addr of the new block won't be the one that is jumped
/// to.
///
BasicBlock *llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
Pass *P, bool MergeIdenticalEdges) {
if (!isCriticalEdge(TI, SuccNum, MergeIdenticalEdges)) return 0;
assert(!isa<IndirectBrInst>(TI) &&
"Cannot split critical edge from IndirectBrInst");
BasicBlock *TIBB = TI->getParent();
BasicBlock *DestBB = TI->getSuccessor(SuccNum);