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[dfsan] Try not to create too many additional basic blocks in functions which

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already have a large number of blocks. Works around a performance issue with
the greedy register allocator.

llvm-svn: 214944
This commit is contained in:
Peter Collingbourne 2014-08-06 00:33:40 +00:00
parent 3005d01057
commit 129ba2ac92
2 changed files with 3057 additions and 18 deletions
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62
lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
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@ -234,6 +234,7 @@ class DataFlowSanitizer : public ModulePass {
FunctionType *DFSanSetLabelFnTy;
FunctionType *DFSanNonzeroLabelFnTy;
Constant *DFSanUnionFn;
Constant *DFSanCheckedUnionFn;
Constant *DFSanUnionLoadFn;
Constant *DFSanUnimplementedFn;
Constant *DFSanSetLabelFn;
@ -280,6 +281,7 @@ struct DFSanFunction {
std::vector<std::pair<PHINode *, PHINode *> > PHIFixups;
DenseSet<Instruction *> SkipInsts;
DenseSet<Value *> NonZeroChecks;
bool AvoidNewBlocks;
struct CachedCombinedShadow {
BasicBlock *Block;
@ -294,6 +296,9 @@ struct DFSanFunction {
IsNativeABI(IsNativeABI), ArgTLSPtr(nullptr), RetvalTLSPtr(nullptr),
LabelReturnAlloca(nullptr) {
DT.recalculate(*F);
// FIXME: Need to track down the register allocator issue which causes poor
// performance in pathological cases with large numbers of basic blocks.
AvoidNewBlocks = F->size() > 1000;
}
Value *getArgTLSPtr();
Value *getArgTLS(unsigned Index, Instruction *Pos);
@ -577,6 +582,15 @@ bool DataFlowSanitizer::runOnModule(Module &M) {
DFSanUnionFn = Mod->getOrInsertFunction("__dfsan_union", DFSanUnionFnTy);
if (Function *F = dyn_cast<Function>(DFSanUnionFn)) {
F->addAttribute(AttributeSet::FunctionIndex, Attribute::NoUnwind);
F->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadNone);
F->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
F->addAttribute(1, Attribute::ZExt);
F->addAttribute(2, Attribute::ZExt);
}
DFSanCheckedUnionFn = Mod->getOrInsertFunction("dfsan_union", DFSanUnionFnTy);
if (Function *F = dyn_cast<Function>(DFSanCheckedUnionFn)) {
F->addAttribute(AttributeSet::FunctionIndex, Attribute::NoUnwind);
F->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadNone);
F->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
F->addAttribute(1, Attribute::ZExt);
@ -585,6 +599,7 @@ bool DataFlowSanitizer::runOnModule(Module &M) {
DFSanUnionLoadFn =
Mod->getOrInsertFunction("__dfsan_union_load", DFSanUnionLoadFnTy);
if (Function *F = dyn_cast<Function>(DFSanUnionLoadFn)) {
F->addAttribute(AttributeSet::FunctionIndex, Attribute::NoUnwind);
F->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadOnly);
F->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
}
@ -603,6 +618,7 @@ bool DataFlowSanitizer::runOnModule(Module &M) {
for (Module::iterator i = M.begin(), e = M.end(); i != e; ++i) {
if (!i->isIntrinsic() &&
i != DFSanUnionFn &&
i != DFSanCheckedUnionFn &&
i != DFSanUnionLoadFn &&
i != DFSanUnimplementedFn &&
i != DFSanSetLabelFn &&
@ -922,23 +938,33 @@ Value *DFSanFunction::combineShadows(Value *V1, Value *V2, Instruction *Pos) {
return CCS.Shadow;
IRBuilder<> IRB(Pos);
BasicBlock *Head = Pos->getParent();
Value *Ne = IRB.CreateICmpNE(V1, V2);
BranchInst *BI = cast<BranchInst>(SplitBlockAndInsertIfThen(
Ne, Pos, /*Unreachable=*/false, DFS.ColdCallWeights, &DT));
IRBuilder<> ThenIRB(BI);
CallInst *Call = ThenIRB.CreateCall2(DFS.DFSanUnionFn, V1, V2);
Call->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
Call->addAttribute(1, Attribute::ZExt);
Call->addAttribute(2, Attribute::ZExt);
if (AvoidNewBlocks) {
CallInst *Call = IRB.CreateCall2(DFS.DFSanCheckedUnionFn, V1, V2);
Call->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
Call->addAttribute(1, Attribute::ZExt);
Call->addAttribute(2, Attribute::ZExt);
BasicBlock *Tail = BI->getSuccessor(0);
PHINode *Phi = PHINode::Create(DFS.ShadowTy, 2, "", Tail->begin());
Phi->addIncoming(Call, Call->getParent());
Phi->addIncoming(V1, Head);
CCS.Block = Pos->getParent();
CCS.Shadow = Call;
} else {
BasicBlock *Head = Pos->getParent();
Value *Ne = IRB.CreateICmpNE(V1, V2);
BranchInst *BI = cast<BranchInst>(SplitBlockAndInsertIfThen(
Ne, Pos, /*Unreachable=*/false, DFS.ColdCallWeights, &DT));
IRBuilder<> ThenIRB(BI);
CallInst *Call = ThenIRB.CreateCall2(DFS.DFSanUnionFn, V1, V2);
Call->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
Call->addAttribute(1, Attribute::ZExt);
Call->addAttribute(2, Attribute::ZExt);
CCS.Block = Tail;
CCS.Shadow = Phi;
BasicBlock *Tail = BI->getSuccessor(0);
PHINode *Phi = PHINode::Create(DFS.ShadowTy, 2, "", Tail->begin());
Phi->addIncoming(Call, Call->getParent());
Phi->addIncoming(V1, Head);
CCS.Block = Tail;
CCS.Shadow = Phi;
}
std::set<Value *> UnionElems;
if (V1Elems != ShadowElements.end()) {
@ -951,9 +977,9 @@ Value *DFSanFunction::combineShadows(Value *V1, Value *V2, Instruction *Pos) {
} else {
UnionElems.insert(V2);
}
ShadowElements[Phi] = std::move(UnionElems);
ShadowElements[CCS.Shadow] = std::move(UnionElems);
return Phi;
return CCS.Shadow;
}
// A convenience function which folds the shadows of each of the operands
@ -1022,7 +1048,7 @@ Value *DFSanFunction::loadShadow(Value *Addr, uint64_t Size, uint64_t Align,
IRB.CreateAlignedLoad(ShadowAddr1, ShadowAlign), Pos);
}
}
if (Size % (64 / DFS.ShadowWidth) == 0) {
if (!AvoidNewBlocks && Size % (64 / DFS.ShadowWidth) == 0) {
// Fast path for the common case where each byte has identical shadow: load
// shadow 64 bits at a time, fall out to a __dfsan_union_load call if any
// shadow is non-equal.

3013
test/Instrumentation/DataFlowSanitizer/union-large.ll Normal file
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