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Fix N^2 instruction ordering comparisons in GVNHoist.

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This fixes GVNHoist's portion of PR28670.

llvm-svn: 276658
This commit is contained in:
Daniel Berlin 2016-07-25 17:24:27 +00:00
parent 20c654aa6e
commit fbf60ece94
1 changed files with 18 additions and 19 deletions
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37
lib/Transforms/Scalar/GVNHoist.cpp
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@ -53,10 +53,10 @@ namespace {
// Provides a sorting function based on the execution order of two instructions.
struct SortByDFSIn {
private:
DenseMap<const BasicBlock *, unsigned> &DFSNumber;
DenseMap<const Value *, unsigned> &DFSNumber;
public:
SortByDFSIn(DenseMap<const BasicBlock *, unsigned> &D) : DFSNumber(D) {}
SortByDFSIn(DenseMap<const Value *, unsigned> &D) : DFSNumber(D) {}
// Returns true when A executes before B.
bool operator()(const Instruction *A, const Instruction *B) const {
@ -74,9 +74,8 @@ public:
if (NA < NB)
return true;
if (NA == NB) {
// Sort them in the order they occur in the same basic block.
BasicBlock::const_iterator AI(A), BI(B);
return std::distance(AI, BI) < 0;
assert (DFSNumber.count(A) && DFSNumber.count(B));
return DFSNumber[A] < DFSNumber[B];
}
return false;
}
@ -196,9 +195,13 @@ public:
VN.setMemDep(MD);
bool Res = false;
// Perform DFS Numbering of blocks and instructions.
unsigned I = 0;
for (const BasicBlock *BB : depth_first(&F.getEntryBlock()))
for (const BasicBlock *BB : depth_first(&F.getEntryBlock())) {
DFSNumber.insert({BB, ++I});
for (auto &Inst: *BB)
DFSNumber.insert({&Inst, ++I});
}
// FIXME: use lazy evaluation of VN to avoid the fix-point computation.
while (1) {
@ -228,7 +231,7 @@ private:
AliasAnalysis *AA;
MemoryDependenceResults *MD;
const bool OptForMinSize;
DenseMap<const BasicBlock *, unsigned> DFSNumber;
DenseMap<const Value *, unsigned> DFSNumber;
BBSideEffectsSet BBSideEffects;
MemorySSA *MSSA;
int HoistedCtr;
@ -290,16 +293,12 @@ private:
}
/* Return true when I1 appears before I2 in the instructions of BB. */
bool firstInBB(BasicBlock *BB, const Instruction *I1, const Instruction *I2) {
for (Instruction &I : *BB) {
if (&I == I1)
return true;
if (&I == I2)
return false;
}
llvm_unreachable("I1 and I2 not found in BB");
bool firstInBB(const Instruction *I1, const Instruction *I2) {
assert (I1->getParent() == I2->getParent());
assert (DFSNumber.count(I1) && DFSNumber.count(I2));
return DFSNumber[I1] < DFSNumber[I2];
}
// Return true when there are users of Def in BB.
bool hasMemoryUseOnPath(MemoryAccess *Def, const BasicBlock *BB,
const Instruction *OldPt) {
@ -323,7 +322,7 @@ private:
return true;
// It is only harmful to hoist when the use is before OldPt.
if (firstInBB(UBB, MU->getMemoryInst(), OldPt))
if (firstInBB(MU->getMemoryInst(), OldPt))
return true;
}
@ -437,7 +436,7 @@ private:
if (NewBB == DBB && !MSSA->isLiveOnEntryDef(D))
if (auto *UD = dyn_cast<MemoryUseOrDef>(D))
if (firstInBB(DBB, NewPt, UD->getMemoryInst()))
if (firstInBB(NewPt, UD->getMemoryInst()))
// Cannot move the load or store to NewPt above its definition in D.
return false;
@ -514,7 +513,7 @@ private:
if (BB == HoistBB) {
NewHoistBB = HoistBB;
NewHoistPt = firstInBB(BB, Insn, HoistPt) ? Insn : HoistPt;
NewHoistPt = firstInBB(Insn, HoistPt) ? Insn : HoistPt;
} else {
NewHoistBB = DT->findNearestCommonDominator(HoistBB, BB);
if (NewHoistBB == BB)