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This change is refactoring only. It moves basic block normalization for invokes to happen before replacement of a call with safepoint in "ReplaceWithStatepoint". Previously it was partly done before replacement of calls with safepoint and partly after call replacement but before RAUW's for gc_relocates, which was confusing.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236829 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Igor Laevsky 2015-05-08 11:59:09 +00:00
parent ca33d72658
commit 4462e6d1b0
1 changed files with 36 additions and 39 deletions
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75
lib/Transforms/Scalar/PlaceSafepoints.cpp
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@ -520,6 +520,23 @@ static bool enableEntrySafepoints(Function &F) { return !NoEntry; }
static bool enableBackedgeSafepoints(Function &F) { return !NoBackedge; }
static bool enableCallSafepoints(Function &F) { return !NoCall; }
// Normalize basic block to make it ready to be target of invoke statepoint.
// Ensure that 'BB' does not have phi nodes. It may require spliting it.
static BasicBlock *normalizeForInvokeSafepoint(BasicBlock *BB,
BasicBlock *InvokeParent) {
BasicBlock *ret = BB;
if (!BB->getUniquePredecessor()) {
ret = SplitBlockPredecessors(BB, InvokeParent, "");
}
// Now that 'ret' has unique predecessor we can safely remove all phi nodes
// from it
FoldSingleEntryPHINodes(ret);
assert(!isa<PHINode>(ret->begin()));
return ret;
}
bool PlaceSafepoints::runOnFunction(Function &F) {
if (F.isDeclaration() || F.empty()) {
@ -673,6 +690,17 @@ bool PlaceSafepoints::runOnFunction(Function &F) {
Results.reserve(ParsePointNeeded.size());
for (size_t i = 0; i < ParsePointNeeded.size(); i++) {
CallSite &CS = ParsePointNeeded[i];
// For invoke statepoints we need to remove all phi nodes at the normal
// destination block.
// Reason for this is that we can place gc_result only after last phi node
// in basic block. We will get malformed code after RAUW for the
// gc_result if one of this phi nodes uses result from the invoke.
if (InvokeInst *Invoke = dyn_cast<InvokeInst>(CS.getInstruction())) {
normalizeForInvokeSafepoint(Invoke->getNormalDest(),
Invoke->getParent());
}
Value *GCResult = ReplaceWithStatepoint(CS, nullptr);
Results.push_back(GCResult);
}
@ -683,20 +711,8 @@ bool PlaceSafepoints::runOnFunction(Function &F) {
CallSite &CS = ParsePointNeeded[i];
Value *GCResult = Results[i];
if (GCResult) {
// In case if we inserted result in a different basic block than the
// original safepoint (this can happen for invokes). We need to be sure
// that
// original result value was not used in any of the phi nodes at the
// beginning of basic block with gc result. Because we know that all such
// blocks will have single predecessor we can safely assume that all phi
// nodes have single entry (because of normalizeBBForInvokeSafepoint).
// Just remove them all here.
if (CS.isInvoke()) {
FoldSingleEntryPHINodes(cast<Instruction>(GCResult)->getParent(),
nullptr);
assert(
!isa<PHINode>(cast<Instruction>(GCResult)->getParent()->begin()));
}
// Can not RAUW for the gc result in case of phi nodes preset.
assert(!isa<PHINode>(cast<Instruction>(GCResult)->getParent()->begin()));
// Replace all uses with the new call
CS.getInstruction()->replaceAllUsesWith(GCResult);
@ -841,28 +857,6 @@ InsertSafepointPoll(DominatorTree &DT, Instruction *term,
assert(ParsePointsNeeded.size() <= calls.size());
}
// Normalize basic block to make it ready to be target of invoke statepoint.
// It means spliting it to have single predecessor. Return newly created BB
// ready to be successor of invoke statepoint.
static BasicBlock *normalizeBBForInvokeSafepoint(BasicBlock *BB,
BasicBlock *InvokeParent) {
BasicBlock *ret = BB;
if (!BB->getUniquePredecessor()) {
ret = SplitBlockPredecessors(BB, InvokeParent, "");
}
// Another requirement for such basic blocks is to not have any phi nodes.
// Since we just ensured that new BB will have single predecessor,
// all phi nodes in it will have one value. Here it would be naturall place
// to
// remove them all. But we can not do this because we are risking to remove
// one of the values stored in liveset of another statepoint. We will do it
// later after placing all safepoints.
return ret;
}
/// Replaces the given call site (Call or Invoke) with a gc.statepoint
/// intrinsic with an empty deoptimization arguments list. This does
/// NOT do explicit relocation for GC support.
@ -937,9 +931,12 @@ static Value *ReplaceWithStatepoint(const CallSite &CS, /* to replace */
Token = Invoke;
// We'll insert the gc.result into the normal block
BasicBlock *NormalDest = normalizeBBForInvokeSafepoint(
ToReplace->getNormalDest(), Invoke->getParent());
Builder.SetInsertPoint(NormalDest->getFirstInsertionPt());
BasicBlock *NormalDest = ToReplace->getNormalDest();
// Can not insert gc.result in case of phi nodes preset.
// Should have removed this cases prior to runnning this function
assert(!isa<PHINode>(NormalDest->begin()));
Instruction *IP = &*(NormalDest->getFirstInsertionPt());
Builder.SetInsertPoint(IP);
} else {
llvm_unreachable("unexpect type of CallSite");
}