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[PredicateInfo] Support existing PredicateType by adding PredicatePHI when needing introduction of phi nodes #151132

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[PredicateInfo] Support existing PredicateType by adding PredicatePHI when needing introduction of phi nodes #151132

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15 changes: 14 additions & 1 deletion llvm/include/llvm/Transforms/Utils/PredicateInfo.h
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Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,7 @@ class Value;
class IntrinsicInst;
class raw_ostream;

enum PredicateType { PT_Branch, PT_Assume, PT_Switch };
enum PredicateType { PT_Branch, PT_Assume, PT_Switch, PT_PHI };

/// Constraint for a predicate of the form "cmp Pred Op, OtherOp", where Op
/// is the value the constraint applies to (the ssa.copy result).
Expand Down Expand Up @@ -171,6 +171,19 @@ class PredicateSwitch : public PredicateWithEdge {
}
};

class PredicatePHI : public PredicateBase {
public:
BasicBlock *PHIBlock;
SmallVector<std::pair<BasicBlock *, PredicateBase *>, 4> IncomingPredicates;

PredicatePHI(Value *Op, BasicBlock *PHIBB)
: PredicateBase(PT_PHI, Op, nullptr), PHIBlock(PHIBB) {}
PredicatePHI() = delete;
static bool classof(const PredicateBase *PB) { return PB->Type == PT_PHI; }

LLVM_ABI std::optional<PredicateConstraint> getConstraint() const;
};

/// Encapsulates PredicateInfo, including all data associated with memory
/// accesses.
class PredicateInfo {
Expand Down
116 changes: 116 additions & 0 deletions llvm/lib/Transforms/Utils/PredicateInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/IR/AssemblyAnnotationWriter.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstIterator.h"
Expand Down Expand Up @@ -213,6 +214,8 @@ class PredicateInfoBuilder {
// whether it returned a valid result.
DenseMap<Value *, unsigned int> ValueInfoNums;

DenseMap<BasicBlock *, SmallVector<Value *, 4>> PHICandidates;

BumpPtrAllocator &Allocator;

ValueInfo &getOrCreateValueInfo(Value *);
Expand All @@ -224,6 +227,10 @@ class PredicateInfoBuilder {
SmallVectorImpl<Value *> &OpsToRename);
void processSwitch(SwitchInst *, BasicBlock *,
SmallVectorImpl<Value *> &OpsToRename);
void identifyPHICandidates(SmallVectorImpl<Value *> &OpsToRename);
void insertPredicatePHIs(Value *Op, BasicBlock *PHIBlock,
SmallVectorImpl<Value *> &OpsToRename);
void processPredicatePHIs(SmallVectorImpl<Value *> &OpsToRename);
void renameUses(SmallVectorImpl<Value *> &OpsToRename);
void addInfoFor(SmallVectorImpl<Value *> &OpsToRename, Value *Op,
PredicateBase *PB);
Expand Down Expand Up @@ -452,6 +459,71 @@ void PredicateInfoBuilder::processSwitch(
}
}

void PredicateInfoBuilder::identifyPHICandidates(
SmallVectorImpl<Value *> &OpsToRename) {
for (Value *Op : OpsToRename) {
const auto &ValueInfo = getValueInfo(Op);
SmallPtrSet<BasicBlock *, 4> DefiningBlocks;
for (const auto *PInfo : ValueInfo.Infos) {
if (auto *PBranch = dyn_cast<PredicateBranch>(PInfo)) {
DefiningBlocks.insert(PBranch->To);
} else if (auto *PSwitch = dyn_cast<PredicateSwitch>(PInfo)) {
DefiningBlocks.insert(PSwitch->To);
}
}

if (DefiningBlocks.size() > 1) {
SmallPtrSet<BasicBlock *, 8> PHIBlocks(DefiningBlocks.begin(),
DefiningBlocks.end());
PHICandidates[*PHIBlocks.begin()].push_back(Op);
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This part is what needs to be fixed, for now I just pushed to make sure the insertion functionality and other logics work well, which it does:

PredicateInfo for function: h5diff
define noundef i32 @h5diff(i32 %0, i1 %1) local_unnamed_addr {
  %cond = icmp eq i32 %0, 0
  br i1 %1, label %3, label %4

3:                                                ; preds = %2
  store i32 1, ptr @p, align 4
; Has predicate info
; branch predicate info { TrueEdge: 1 Comparison:  %cond = icmp eq i32 %0, 0 Edge: [label %3,label %5], RenamedOp: %cond }
  %cond.0 = call i1 @llvm.ssa.copy.i1(i1 %cond)
; Has predicate info
; branch predicate info { TrueEdge: 1 Comparison:  %cond = icmp eq i32 %0, 0 Edge: [label %3,label %5], RenamedOp: %0 }
  %.0 = call i32 @llvm.ssa.copy.i32(i32 %0)
  br i1 %cond, label %5, label %common.ret

common.ret:                                       ; preds = %5, %4, %3
  ret i32 0

4:                                                ; preds = %2
  store i32 2, ptr @p, align 4
; Has predicate info
; branch predicate info { TrueEdge: 1 Comparison:  %cond = icmp eq i32 %0, 0 Edge: [label %4,label %5], RenamedOp: %cond }
  %cond.1 = call i1 @llvm.ssa.copy.i1(i1 %cond)
; Has predicate info
; branch predicate info { TrueEdge: 1 Comparison:  %cond = icmp eq i32 %0, 0 Edge: [label %4,label %5], RenamedOp: %0 }
  %.1 = call i32 @llvm.ssa.copy.i32(i32 %0)
  br i1 %cond, label %5, label %common.ret

5:                                                ; preds = %4, %3
  %.predicate.phi = phi i32 [ %.1, %4 ], [ %.0, %3 ]
  %cond.predicate.phi = phi i1 [ %cond.1, %4 ], [ %cond.0, %3 ]
; Has predicate info
; phi predicate info { PHIBlock: label %5 IncomingEdges: 2, RenamedOp: %0 }
  %6 = call i32 @llvm.ssa.copy.i32(i32 %0)
  store i32 %6, ptr @p, align 4
  br label %common.ret
}

}
}
}

void PredicateInfoBuilder::insertPredicatePHIs(
Value *Op, BasicBlock *PHIBlock, SmallVectorImpl<Value *> &OpsToRename) {
IRBuilder<> Builder(&PHIBlock->front());

PHINode *PHI = Builder.CreatePHI(Op->getType(), pred_size(PHIBlock),
Op->getName() + ".predicate.phi");
PredicatePHI *PPHI = new (Allocator) PredicatePHI(Op, PHIBlock);

PPHI->RenamedOp = PHI;

const auto &ValueInfo = getValueInfo(Op);
for (BasicBlock *Pred : predecessors(PHIBlock)) {
Value *IncomingValue = nullptr;
for (const auto *PInfo : ValueInfo.Infos) {
if (auto *PBranch = dyn_cast<PredicateBranch>(PInfo)) {
if (PBranch->From == Pred && PBranch->To == PHIBlock) {
PPHI->IncomingPredicates.push_back(
{Pred, const_cast<PredicateBase *>(PInfo)});
IncomingValue = PBranch->OriginalOp;
}
} else if (auto *PSwitch = dyn_cast<PredicateSwitch>(PInfo)) {
if (PSwitch->From == Pred && PSwitch->To == PHIBlock) {
PPHI->IncomingPredicates.push_back(
{Pred, const_cast<PredicateBase *>(PInfo)});
IncomingValue = PSwitch->OriginalOp;
}
}
}
PHI->addIncoming(IncomingValue, Pred);
}

addInfoFor(OpsToRename, Op, PPHI);
}

void PredicateInfoBuilder::processPredicatePHIs(
SmallVectorImpl<Value *> &OpsToRename) {
for (const auto &PHICandidate : PHICandidates) {
BasicBlock *PHIBlock = PHICandidate.first;
for (Value *Op : PHICandidate.second) {
insertPredicatePHIs(Op, PHIBlock, OpsToRename);
}
}
}

// Build predicate info for our function
void PredicateInfoBuilder::buildPredicateInfo() {
DT.updateDFSNumbers();
Expand All @@ -478,6 +550,10 @@ void PredicateInfoBuilder::buildPredicateInfo() {
if (DT.isReachableFromEntry(II->getParent()))
processAssume(II, II->getParent(), OpsToRename);
}

identifyPHICandidates(OpsToRename);
processPredicatePHIs(OpsToRename);

// Now rename all our operations.
renameUses(OpsToRename);
}
Expand Down Expand Up @@ -535,6 +611,12 @@ Value *PredicateInfoBuilder::materializeStack(unsigned int &Counter,
CreateSSACopy(B, Op, Op->getName() + "." + Twine(Counter++));
PI.PredicateMap.insert({PIC, ValInfo});
Result.Def = PIC;
} else if (isa<PredicatePHI>(ValInfo)) {
auto *PPHI = dyn_cast<PredicatePHI>(ValInfo);
IRBuilder<> B(&*PPHI->PHIBlock->getFirstInsertionPt());
CallInst *PIC = CreateSSACopy(B, Op);
PI.PredicateMap.insert({PIC, ValInfo});
Result.Def = PIC;
} else {
auto *PAssume = dyn_cast<PredicateAssume>(ValInfo);
assert(PAssume &&
Expand Down Expand Up @@ -623,6 +705,15 @@ void PredicateInfoBuilder::renameUses(SmallVectorImpl<Value *> &OpsToRename) {
OrderedUses.push_back(VD);
}
}
} else if (const auto *PPHI = dyn_cast<PredicatePHI>(PossibleCopy)) {
VD.LocalNum = LN_First;
auto *DomNode = DT.getNode(PPHI->PHIBlock);
if (DomNode) {
VD.DFSIn = DomNode->getDFSNumIn();
VD.DFSOut = DomNode->getDFSNumOut();
VD.PInfo = PossibleCopy;
OrderedUses.push_back(VD);
}
}
}

Expand Down Expand Up @@ -773,10 +864,31 @@ std::optional<PredicateConstraint> PredicateBase::getConstraint() const {
}

return {{CmpInst::ICMP_EQ, cast<PredicateSwitch>(this)->CaseValue}};
case PT_PHI:
return cast<PredicatePHI>(this)->getConstraint();
}
llvm_unreachable("Unknown predicate type");
}

std::optional<PredicateConstraint> PredicatePHI::getConstraint() const {
if (IncomingPredicates.empty())
return std::nullopt;

auto FirstConstraint = IncomingPredicates[0].second->getConstraint();
if (!FirstConstraint)
return std::nullopt;

for (size_t I = 1; I < IncomingPredicates.size(); ++I) {
auto Constraint = IncomingPredicates[I].second->getConstraint();
if (!Constraint || Constraint->Predicate != FirstConstraint->Predicate ||
Constraint->OtherOp != FirstConstraint->OtherOp) {
return std::nullopt;
}
}

return FirstConstraint;
}

void PredicateInfo::verifyPredicateInfo() const {}

// Replace ssa_copy calls created by PredicateInfo with their operand.
Expand Down Expand Up @@ -838,6 +950,10 @@ class PredicateInfoAnnotatedWriter : public AssemblyAnnotationWriter {
} else if (const auto *PA = dyn_cast<PredicateAssume>(PI)) {
OS << "; assume predicate info {"
<< " Comparison:" << *PA->Condition;
} else if (const auto *PP = dyn_cast<PredicatePHI>(PI)) {
OS << "; phi predicate info { PHIBlock: ";
PP->PHIBlock->printAsOperand(OS);
OS << " IncomingEdges: " << PP->IncomingPredicates.size();
}
OS << ", RenamedOp: ";
PI->RenamedOp->printAsOperand(OS, false);
Expand Down
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