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[NFC] Prepare GuardWidening for widening of cond branches

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llvm-svn: 338229
This commit is contained in:
Max Kazantsev 2018-07-30 07:07:32 +00:00
parent 06018234e8
commit 2a549dc9b1
1 changed files with 61 additions and 27 deletions
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88
lib/Transforms/Scalar/GuardWidening.cpp
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@ -75,21 +75,33 @@ class GuardWideningImpl {
/// The set of guards whose conditions have been widened into dominating
/// guards.
SmallVector<IntrinsicInst *, 16> EliminatedGuards;
SmallVector<Instruction *, 16> EliminatedGuards;
/// The set of guards which have been widened to include conditions to other
/// guards.
DenseSet<IntrinsicInst *> WidenedGuards;
DenseSet<Instruction *> WidenedGuards;
/// Try to eliminate guard \p Guard by widening it into an earlier dominating
/// guard. \p DFSI is the DFS iterator on the dominator tree that is
/// currently visiting the block containing \p Guard, and \p GuardsPerBlock
/// maps BasicBlocks to the set of guards seen in that block.
bool eliminateGuardViaWidening(
IntrinsicInst *Guard, const df_iterator<DomTreeNode *> &DFSI,
const DenseMap<BasicBlock *, SmallVector<IntrinsicInst *, 8>> &
Instruction *Guard, const df_iterator<DomTreeNode *> &DFSI,
const DenseMap<BasicBlock *, SmallVector<Instruction *, 8>> &
GuardsPerBlock);
// Get the condition from \p GuardInst.
Value *getGuardCondition(Instruction *GuardInst);
// Set the condition for \p GuardInst.
void setGuardCondition(Instruction *GuardInst, Value *NewCond);
// Whether or not the particular instruction is a guard.
bool isGuard(const Instruction *I);
// Eliminates the guard instruction properly.
void eliminateGuard(Instruction *GuardInst);
/// Used to keep track of which widening potential is more effective.
enum WideningScore {
/// Don't widen.
@ -113,9 +125,9 @@ class GuardWideningImpl {
/// Compute the score for widening the condition in \p DominatedGuard
/// (contained in \p DominatedGuardLoop) into \p DominatingGuard (contained in
/// \p DominatingGuardLoop).
WideningScore computeWideningScore(IntrinsicInst *DominatedGuard,
WideningScore computeWideningScore(Instruction *DominatedGuard,
Loop *DominatedGuardLoop,
IntrinsicInst *DominatingGuard,
Instruction *DominatingGuard,
Loop *DominatingGuardLoop);
/// Helper to check if \p V can be hoisted to \p InsertPos.
@ -206,10 +218,10 @@ class GuardWideningImpl {
/// Widen \p ToWiden to fail if \p NewCondition is false (in addition to
/// whatever it is already checking).
void widenGuard(IntrinsicInst *ToWiden, Value *NewCondition) {
void widenGuard(Instruction *ToWiden, Value *NewCondition) {
Value *Result;
widenCondCommon(ToWiden->getArgOperand(0), NewCondition, ToWiden, Result);
ToWiden->setArgOperand(0, Result);
widenCondCommon(ToWiden->getOperand(0), NewCondition, ToWiden, Result);
setGuardCondition(ToWiden, Result);
}
public:
@ -225,9 +237,7 @@ public:
}
bool GuardWideningImpl::run() {
using namespace llvm::PatternMatch;
DenseMap<BasicBlock *, SmallVector<IntrinsicInst *, 8>> GuardsInBlock;
DenseMap<BasicBlock *, SmallVector<Instruction *, 8>> GuardsInBlock;
bool Changed = false;
for (auto DFI = df_begin(Root), DFE = df_end(Root);
@ -239,8 +249,8 @@ bool GuardWideningImpl::run() {
auto &CurrentList = GuardsInBlock[BB];
for (auto &I : *BB)
if (match(&I, m_Intrinsic<Intrinsic::experimental_guard>()))
CurrentList.push_back(cast<IntrinsicInst>(&I));
if (isGuard(&I))
CurrentList.push_back(cast<Instruction>(&I));
for (auto *II : CurrentList)
Changed |= eliminateGuardViaWidening(II, DFI, GuardsInBlock);
@ -249,16 +259,16 @@ bool GuardWideningImpl::run() {
assert(EliminatedGuards.empty() || Changed);
for (auto *II : EliminatedGuards)
if (!WidenedGuards.count(II))
II->eraseFromParent();
eliminateGuard(II);
return Changed;
}
bool GuardWideningImpl::eliminateGuardViaWidening(
IntrinsicInst *GuardInst, const df_iterator<DomTreeNode *> &DFSI,
const DenseMap<BasicBlock *, SmallVector<IntrinsicInst *, 8>> &
Instruction *GuardInst, const df_iterator<DomTreeNode *> &DFSI,
const DenseMap<BasicBlock *, SmallVector<Instruction *, 8>> &
GuardsInBlock) {
IntrinsicInst *BestSoFar = nullptr;
Instruction *BestSoFar = nullptr;
auto BestScoreSoFar = WS_IllegalOrNegative;
auto *GuardInstLoop = LI.getLoopFor(GuardInst->getParent());
@ -302,8 +312,8 @@ bool GuardWideningImpl::eliminateGuardViaWidening(
for (auto *Candidate : make_range(I, E)) {
auto Score =
computeWideningScore(GuardInst, GuardInstLoop, Candidate, CurLoop);
LLVM_DEBUG(dbgs() << "Score between " << *GuardInst->getArgOperand(0)
<< " and " << *Candidate->getArgOperand(0) << " is "
LLVM_DEBUG(dbgs() << "Score between " << *getGuardCondition(GuardInst)
<< " and " << *getGuardCondition(Candidate) << " is "
<< scoreTypeToString(Score) << "\n");
if (Score > BestScoreSoFar) {
BestScoreSoFar = Score;
@ -323,16 +333,40 @@ bool GuardWideningImpl::eliminateGuardViaWidening(
LLVM_DEBUG(dbgs() << "Widening " << *GuardInst << " into " << *BestSoFar
<< " with score " << scoreTypeToString(BestScoreSoFar)
<< "\n");
widenGuard(BestSoFar, GuardInst->getArgOperand(0));
GuardInst->setArgOperand(0, ConstantInt::getTrue(GuardInst->getContext()));
widenGuard(BestSoFar, getGuardCondition(GuardInst));
setGuardCondition(GuardInst, ConstantInt::getTrue(GuardInst->getContext()));
EliminatedGuards.push_back(GuardInst);
WidenedGuards.insert(BestSoFar);
return true;
}
Value *GuardWideningImpl::getGuardCondition(Instruction *GuardInst) {
IntrinsicInst *GI = cast<IntrinsicInst>(GuardInst);
assert(GI->getIntrinsicID() == Intrinsic::experimental_guard &&
"Bad guard intrinsic?");
return GI->getArgOperand(0);
}
void GuardWideningImpl::setGuardCondition(Instruction *GuardInst,
Value *NewCond) {
IntrinsicInst *GI = cast<IntrinsicInst>(GuardInst);
assert(GI->getIntrinsicID() == Intrinsic::experimental_guard &&
"Bad guard intrinsic?");
GI->setArgOperand(0, NewCond);
}
bool GuardWideningImpl::isGuard(const Instruction* I) {
using namespace llvm::PatternMatch;
return match(I, m_Intrinsic<Intrinsic::experimental_guard>());
}
void GuardWideningImpl::eliminateGuard(Instruction *GuardInst) {
GuardInst->eraseFromParent();
}
GuardWideningImpl::WideningScore GuardWideningImpl::computeWideningScore(
IntrinsicInst *DominatedGuard, Loop *DominatedGuardLoop,
IntrinsicInst *DominatingGuard, Loop *DominatingGuardLoop) {
Instruction *DominatedGuard, Loop *DominatedGuardLoop,
Instruction *DominatingGuard, Loop *DominatingGuardLoop) {
bool HoistingOutOfLoop = false;
if (DominatingGuardLoop != DominatedGuardLoop) {
@ -345,7 +379,7 @@ GuardWideningImpl::WideningScore GuardWideningImpl::computeWideningScore(
HoistingOutOfLoop = true;
}
if (!isAvailableAt(DominatedGuard->getArgOperand(0), DominatingGuard))
if (!isAvailableAt(getGuardCondition(DominatedGuard), DominatingGuard))
return WS_IllegalOrNegative;
// If the guard was conditional executed, it may never be reached
@ -356,8 +390,8 @@ GuardWideningImpl::WideningScore GuardWideningImpl::computeWideningScore(
// here. TODO: evaluate cost model for spurious deopt
// NOTE: As written, this also lets us hoist right over another guard which
// is essentially just another spelling for control flow.
if (isWideningCondProfitable(DominatedGuard->getArgOperand(0),
DominatingGuard->getArgOperand(0)))
if (isWideningCondProfitable(getGuardCondition(DominatedGuard),
getGuardCondition(DominatingGuard)))
return HoistingOutOfLoop ? WS_VeryPositive : WS_Positive;
if (HoistingOutOfLoop)