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[DFAJumpThreading] Unify getNextCaseSuccessor #166422

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[DFAJumpThreading] Unify getNextCaseSuccessor #166422

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88 changes: 45 additions & 43 deletions llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -575,7 +575,7 @@ struct AllSwitchPaths {
AllSwitchPaths(const MainSwitch *MSwitch, OptimizationRemarkEmitter *ORE,
LoopInfo *LI, Loop *L)
: Switch(MSwitch->getInstr()), SwitchBlock(Switch->getParent()), ORE(ORE),
LI(LI), SwitchOuterLoop(L) {}
DefaultDest(nullptr), LI(LI), SwitchOuterLoop(L) {}

std::vector<ThreadingPath> &getThreadingPaths() { return TPaths; }
unsigned getNumThreadingPaths() { return TPaths.size(); }
Expand All @@ -587,6 +587,30 @@ struct AllSwitchPaths {
unifyTPaths();
}

/// Fast helper to get the successor corresponding to a particular case value
/// for a switch statement.
BasicBlock *getNextCaseSuccessor(const APInt &NextState) {
// Precompute the value => successor mapping
if (CaseValToDest.empty()) {
for (auto Case : Switch->cases()) {
APInt CaseVal = Case.getCaseValue()->getValue();
CaseValToDest[CaseVal] = Case.getCaseSuccessor();
}
DefaultDest = Switch->getDefaultDest();
}

auto SuccIt = CaseValToDest.find(NextState);
return SuccIt == CaseValToDest.end() ? DefaultDest : SuccIt->second;
}

void updateDefaultDest(BasicBlock *DefaultDest) {
this->DefaultDest = DefaultDest;
}

void updateNextCase(const APInt &NextState, BasicBlock *NextCase) {
CaseValToDest[NextState] = NextCase;
}

private:
// Value: an instruction that defines a switch state;
// Key: the parent basic block of that instruction.
Expand Down Expand Up @@ -818,22 +842,6 @@ struct AllSwitchPaths {
TPaths = std::move(TempList);
}

/// Fast helper to get the successor corresponding to a particular case value
/// for a switch statement.
BasicBlock *getNextCaseSuccessor(const APInt &NextState) {
// Precompute the value => successor mapping
if (CaseValToDest.empty()) {
for (auto Case : Switch->cases()) {
APInt CaseVal = Case.getCaseValue()->getValue();
CaseValToDest[CaseVal] = Case.getCaseSuccessor();
}
}

auto SuccIt = CaseValToDest.find(NextState);
return SuccIt == CaseValToDest.end() ? Switch->getDefaultDest()
: SuccIt->second;
}

// Two states are equivalent if they have the same switch destination.
// Unify the states in different threading path if the states are equivalent.
void unifyTPaths() {
Expand All @@ -858,6 +866,7 @@ struct AllSwitchPaths {
OptimizationRemarkEmitter *ORE;
std::vector<ThreadingPath> TPaths;
DenseMap<APInt, BasicBlock *> CaseValToDest;
BasicBlock *DefaultDest;
LoopInfo *LI;
Loop *SwitchOuterLoop;
};
Expand Down Expand Up @@ -1159,24 +1168,6 @@ struct TransformDFA {
SSAUpdate.RewriteAllUses(&DTU->getDomTree());
}

/// Helper to get the successor corresponding to a particular case value for
/// a switch statement.
/// TODO: Unify it with SwitchPaths->getNextCaseSuccessor(SwitchInst *Switch)
/// by updating cached value => successor mapping during threading.
static BasicBlock *getNextCaseSuccessor(SwitchInst *Switch,
const APInt &NextState) {
BasicBlock *NextCase = nullptr;
for (auto Case : Switch->cases()) {
if (Case.getCaseValue()->getValue() == NextState) {
NextCase = Case.getCaseSuccessor();
break;
}
}
if (!NextCase)
NextCase = Switch->getDefaultDest();
return NextCase;
}

/// Clones a basic block, and adds it to the CFG.
///
/// This function also includes updating phi nodes in the successors of the
Expand Down Expand Up @@ -1231,8 +1222,7 @@ struct TransformDFA {
// If BB is the last block in the path, we can simply update the one case
// successor that will be reached.
if (BB == SwitchPaths->getSwitchBlock()) {
SwitchInst *Switch = SwitchPaths->getSwitchInst();
BasicBlock *NextCase = getNextCaseSuccessor(Switch, NextState);
BasicBlock *NextCase = SwitchPaths->getNextCaseSuccessor(NextState);
BlocksToUpdate.push_back(NextCase);
BasicBlock *ClonedSucc = getClonedBB(NextCase, NextState, DuplicateMap);
if (ClonedSucc)
Expand Down Expand Up @@ -1283,6 +1273,15 @@ struct TransformDFA {
return;

Instruction *PrevTerm = PrevBB->getTerminator();
// Update cached value => destination mapping.
if (PrevTerm == SwitchPaths->getSwitchInst()) {
for (auto Case : SwitchPaths->getSwitchInst()->cases())
if (Case.getCaseSuccessor() == OldBB)
SwitchPaths->updateNextCase(Case.getCaseValue()->getValue(), NewBB);
if (SwitchPaths->getSwitchInst()->getDefaultDest() == OldBB)
SwitchPaths->updateDefaultDest(NewBB);
}
// Replace actual successors.
for (unsigned Idx = 0; Idx < PrevTerm->getNumSuccessors(); Idx++) {
if (PrevTerm->getSuccessor(Idx) == OldBB) {
OldBB->removePredecessor(PrevBB, /* KeepOneInputPHIs = */ true);
Expand Down Expand Up @@ -1341,17 +1340,20 @@ struct TransformDFA {
// updated yet
if (!isa<SwitchInst>(LastBlock->getTerminator()))
return;
SwitchInst *Switch = cast<SwitchInst>(LastBlock->getTerminator());
BasicBlock *NextCase = getNextCaseSuccessor(Switch, NextState);
assert(BB->getTerminator() == SwitchPaths->getSwitchInst() &&
"Original last block must contain the threaded switch");
BasicBlock *NextCase = SwitchPaths->getNextCaseSuccessor(NextState);

std::vector<DominatorTree::UpdateType> DTUpdates;
SmallPtrSet<BasicBlock *, 4> SuccSet;
for (BasicBlock *Succ : successors(LastBlock)) {
if (Succ != NextCase && SuccSet.insert(Succ).second)
for (BasicBlock *Succ : successors(LastBlock))
if (SuccSet.insert(Succ).second && Succ != NextCase)
DTUpdates.push_back({DominatorTree::Delete, LastBlock, Succ});
}

Switch->eraseFromParent();
if (!SuccSet.count(NextCase))
DTUpdates.push_back({DominatorTree::Insert, LastBlock, NextCase});

LastBlock->getTerminator()->eraseFromParent();
BranchInst::Create(NextCase, LastBlock);

DTU->applyUpdates(DTUpdates);
Expand Down
10 changes: 5 additions & 5 deletions llvm/test/Transforms/DFAJumpThreading/dfa-unfold-select.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -109,7 +109,7 @@ define i32 @test2(i32 %num) {
; CHECK: for.body.jt3:
; CHECK-NEXT: [[COUNT_JT3:%.*]] = phi i32 [ [[INC_JT3:%.*]], [[FOR_INC_JT3:%.*]] ]
; CHECK-NEXT: [[STATE_JT3:%.*]] = phi i32 [ [[STATE_NEXT_JT3:%.*]], [[FOR_INC_JT3]] ]
; CHECK-NEXT: br label [[FOR_INC]]
; CHECK-NEXT: br label [[FOR_INC_JT1]]
; CHECK: case1:
; CHECK-NEXT: [[COUNT6:%.*]] = phi i32 [ [[COUNT_JT1]], [[FOR_BODY_JT1:%.*]] ], [ [[COUNT]], [[FOR_BODY]] ]
; CHECK-NEXT: [[CMP_C1:%.*]] = icmp slt i32 [[COUNT6]], 50
Expand Down Expand Up @@ -156,8 +156,8 @@ define i32 @test2(i32 %num) {
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI4_JT2:%.*]] = phi i32 [ 2, [[STATE1_1_SI_UNFOLD_TRUE:%.*]] ]
; CHECK-NEXT: br label [[FOR_INC_JT2]]
; CHECK: for.inc:
; CHECK-NEXT: [[COUNT5:%.*]] = phi i32 [ [[COUNT_JT3]], [[FOR_BODY_JT3:%.*]] ], [ undef, [[STATE1_1_SI_UNFOLD_TRUE]] ], [ [[COUNT6]], [[STATE1_1_SI_UNFOLD_FALSE]] ], [ undef, [[STATE1_2_SI_UNFOLD_FALSE:%.*]] ], [ [[COUNT]], [[STATE2_2_SI_UNFOLD_FALSE]] ]
; CHECK-NEXT: [[STATE_NEXT]] = phi i32 [ [[STATE2_1_SI_UNFOLD_PHI]], [[STATE2_2_SI_UNFOLD_FALSE]] ], [ poison, [[STATE1_2_SI_UNFOLD_FALSE]] ], [ poison, [[STATE1_1_SI_UNFOLD_TRUE]] ], [ [[DOTSI_UNFOLD_PHI4]], [[STATE1_1_SI_UNFOLD_FALSE]] ], [ 1, [[FOR_BODY_JT3]] ]
; CHECK-NEXT: [[COUNT5:%.*]] = phi i32 [ undef, [[STATE1_1_SI_UNFOLD_TRUE]] ], [ [[COUNT6]], [[STATE1_1_SI_UNFOLD_FALSE]] ], [ undef, [[STATE1_2_SI_UNFOLD_FALSE:%.*]] ], [ [[COUNT]], [[STATE2_2_SI_UNFOLD_FALSE]] ]
; CHECK-NEXT: [[STATE_NEXT]] = phi i32 [ [[STATE2_1_SI_UNFOLD_PHI]], [[STATE2_2_SI_UNFOLD_FALSE]] ], [ poison, [[STATE1_2_SI_UNFOLD_FALSE]] ], [ poison, [[STATE1_1_SI_UNFOLD_TRUE]] ], [ [[DOTSI_UNFOLD_PHI4]], [[STATE1_1_SI_UNFOLD_FALSE]] ]
; CHECK-NEXT: [[INC]] = add nsw i32 [[COUNT5]], 1
; CHECK-NEXT: [[CMP_EXIT:%.*]] = icmp slt i32 [[INC]], [[NUM:%.*]]
; CHECK-NEXT: br i1 [[CMP_EXIT]], label [[FOR_BODY]], label [[FOR_END:%.*]]
Expand All @@ -167,8 +167,8 @@ define i32 @test2(i32 %num) {
; CHECK-NEXT: [[CMP_EXIT_JT2:%.*]] = icmp slt i32 [[INC_JT2]], [[NUM]]
; CHECK-NEXT: br i1 [[CMP_EXIT_JT2]], label [[FOR_BODY_JT2:%.*]], label [[FOR_END]]
; CHECK: for.inc.jt1:
; CHECK-NEXT: [[COUNT7:%.*]] = phi i32 [ [[COUNT6]], [[STATE1_1_SI_UNFOLD_TRUE_JT1]] ], [ [[COUNT]], [[STATE2_2_SI_UNFOLD_FALSE_JT1]] ], [ [[COUNT]], [[FOR_BODY]] ]
; CHECK-NEXT: [[STATE_NEXT_JT1]] = phi i32 [ 1, [[FOR_BODY]] ], [ [[STATE2_1_SI_UNFOLD_PHI_JT1]], [[STATE2_2_SI_UNFOLD_FALSE_JT1]] ], [ [[DOTSI_UNFOLD_PHI3_JT1]], [[STATE1_1_SI_UNFOLD_TRUE_JT1]] ]
; CHECK-NEXT: [[COUNT7:%.*]] = phi i32 [ [[COUNT_JT3]], [[FOR_BODY_JT3:%.*]] ], [ [[COUNT6]], [[STATE1_1_SI_UNFOLD_TRUE_JT1]] ], [ [[COUNT]], [[STATE2_2_SI_UNFOLD_FALSE_JT1]] ], [ [[COUNT]], [[FOR_BODY]] ]
; CHECK-NEXT: [[STATE_NEXT_JT1]] = phi i32 [ 1, [[FOR_BODY]] ], [ 1, [[FOR_BODY_JT3]] ], [ [[STATE2_1_SI_UNFOLD_PHI_JT1]], [[STATE2_2_SI_UNFOLD_FALSE_JT1]] ], [ [[DOTSI_UNFOLD_PHI3_JT1]], [[STATE1_1_SI_UNFOLD_TRUE_JT1]] ]
; CHECK-NEXT: [[INC_JT1]] = add nsw i32 [[COUNT7]], 1
; CHECK-NEXT: [[CMP_EXIT_JT1:%.*]] = icmp slt i32 [[INC_JT1]], [[NUM]]
; CHECK-NEXT: br i1 [[CMP_EXIT_JT1]], label [[FOR_BODY_JT1]], label [[FOR_END]]
Expand Down