//===- PredicateInfo.h - Build PredicateInfo ----------------------*-C++-*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file implements the PredicateInfo analysis, which creates an Extended
/// SSA form for operations used in branch comparisons and llvm.assume
/// comparisons.
///
/// Copies of these operations are inserted into the true/false edge (and after
/// assumes), and information attached to the copies. All uses of the original
/// operation in blocks dominated by the true/false edge (and assume), are
/// replaced with uses of the copies. This enables passes to easily and sparsely
/// propagate condition based info into the operations that may be affected.
///
/// Example:
/// %cmp = icmp eq i32 %x, 50
/// br i1 %cmp, label %true, label %false
/// true:
/// ret i32 %x
/// false:
/// ret i32 1
///
/// will become
///
/// %cmp = icmp eq i32, %x, 50
/// br i1 %cmp, label %true, label %false
/// true:
/// %x.0 = call \@llvm.ssa_copy.i32(i32 %x)
/// ret i32 %x.0
/// false:
/// ret i32 1
///
/// Using getPredicateInfoFor on x.0 will give you the comparison it is
/// dominated by (the icmp), and that you are located in the true edge of that
/// comparison, which tells you x.0 is 50.
///
/// In order to reduce the number of copies inserted, predicateinfo is only
/// inserted where it would actually be live. This means if there are no uses of
/// an operation dominated by the branch edges, or by an assume, the associated
/// predicate info is never inserted.
///
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_TRANSFORMS_UTILS_PREDICATEINFO_H
#define LLVM_TRANSFORMS_UTILS_PREDICATEINFO_H
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/ilist.h"
#include "llvm/ADT/ilist_node.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/PassManager.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/Pass.h"
namespace llvm {
class AssumptionCache;
class DominatorTree;
class Function;
class Value;
class IntrinsicInst;
class raw_ostream;
enum PredicateType { PT_Branch, PT_Assume, PT_Switch };
/// Constraint for a predicate of the form "cmp Pred Op, OtherOp", where Op
/// is the value the constraint applies to (the ssa.copy result).
struct PredicateConstraint {
CmpInst::Predicate Predicate;
Value *OtherOp;
};
// Base class for all predicate information we provide.
// All of our predicate information has at least a comparison.
class PredicateBase : public ilist_node<PredicateBase> {
public:
PredicateType Type;
// The original operand before we renamed it.
// This can be use by passes, when destroying predicateinfo, to know
// whether they can just drop the intrinsic, or have to merge metadata.
Value *OriginalOp;
// The renamed operand in the condition used for this predicate. For nested
// predicates, this is different to OriginalOp which refers to the initial
// operand.
Value *RenamedOp;
// The condition associated with this predicate.
Value *Condition;
PredicateBase(const PredicateBase &) = delete;
PredicateBase &operator=(const PredicateBase &) = delete;
PredicateBase() = delete;
virtual ~PredicateBase() = default;
static bool classof(const PredicateBase *PB) {
return PB->Type == PT_Assume || PB->Type == PT_Branch ||
PB->Type == PT_Switch;
}
/// Fetch condition in the form of PredicateConstraint, if possible.
std::optional<PredicateConstraint> getConstraint() const;
protected:
PredicateBase(PredicateType PT, Value *Op, Value *Condition)
: Type(PT), OriginalOp(Op), Condition(Condition) {}
};
// Provides predicate information for assumes. Since assumes are always true,
// we simply provide the assume instruction, so you can tell your relative
// position to it.
class PredicateAssume : public PredicateBase {
public:
IntrinsicInst *AssumeInst;
PredicateAssume(Value *Op, IntrinsicInst *AssumeInst, Value *Condition)
: PredicateBase(PT_Assume, Op, Condition), AssumeInst(AssumeInst) {}
PredicateAssume() = delete;
static bool classof(const PredicateBase *PB) {
return PB->Type == PT_Assume;
}
};
// Mixin class for edge predicates. The FROM block is the block where the
// predicate originates, and the TO block is the block where the predicate is
// valid.
class PredicateWithEdge : public PredicateBase {
public:
BasicBlock *From;
BasicBlock *To;
PredicateWithEdge() = delete;
static bool classof(const PredicateBase *PB) {
return PB->Type == PT_Branch || PB->Type == PT_Switch;
}
protected:
PredicateWithEdge(PredicateType PType, Value *Op, BasicBlock *From,
BasicBlock *To, Value *Cond)
: PredicateBase(PType, Op, Cond), From(From), To(To) {}
};
// Provides predicate information for branches.
class PredicateBranch : public PredicateWithEdge {
public:
// If true, SplitBB is the true successor, otherwise it's the false successor.
bool TrueEdge;
PredicateBranch(Value *Op, BasicBlock *BranchBB, BasicBlock *SplitBB,
Value *Condition, bool TakenEdge)
: PredicateWithEdge(PT_Branch, Op, BranchBB, SplitBB, Condition),
TrueEdge(TakenEdge) {}
PredicateBranch() = delete;
static bool classof(const PredicateBase *PB) {
return PB->Type == PT_Branch;
}
};
class PredicateSwitch : public PredicateWithEdge {
public:
Value *CaseValue;
// This is the switch instruction.
SwitchInst *Switch;
PredicateSwitch(Value *Op, BasicBlock *SwitchBB, BasicBlock *TargetBB,
Value *CaseValue, SwitchInst *SI)
: PredicateWithEdge(PT_Switch, Op, SwitchBB, TargetBB,
SI->getCondition()),
CaseValue(CaseValue), Switch(SI) {}
PredicateSwitch() = delete;
static bool classof(const PredicateBase *PB) {
return PB->Type == PT_Switch;
}
};
/// Encapsulates PredicateInfo, including all data associated with memory
/// accesses.
class PredicateInfo {
public:
PredicateInfo(Function &, DominatorTree &, AssumptionCache &);
~PredicateInfo();
void verifyPredicateInfo() const;
void dump() const;
void print(raw_ostream &) const;
const PredicateBase *getPredicateInfoFor(const Value *V) const {
return PredicateMap.lookup(V);
}
protected:
// Used by PredicateInfo annotater, dumpers, and wrapper pass.
friend class PredicateInfoAnnotatedWriter;
friend class PredicateInfoPrinterLegacyPass;
friend class PredicateInfoBuilder;
private:
Function &F;
// This owns the all the predicate infos in the function, placed or not.
iplist<PredicateBase> AllInfos;
// This maps from copy operands to Predicate Info. Note that it does not own
// the Predicate Info, they belong to the ValueInfo structs in the ValueInfos
// vector.
DenseMap<const Value *, const PredicateBase *> PredicateMap;
// The set of ssa_copy declarations we created with our custom mangling.
SmallSet<AssertingVH<Function>, 20> CreatedDeclarations;
};
// This pass does eager building and then printing of PredicateInfo. It is used
// by
// the tests to be able to build, dump, and verify PredicateInfo.
class PredicateInfoPrinterLegacyPass : public FunctionPass {
public:
PredicateInfoPrinterLegacyPass();
static char ID;
bool runOnFunction(Function &) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
};
/// Printer pass for \c PredicateInfo.
class PredicateInfoPrinterPass
: public PassInfoMixin<PredicateInfoPrinterPass> {
raw_ostream &OS;
public:
explicit PredicateInfoPrinterPass(raw_ostream &OS) : OS(OS) {}
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
};
/// Verifier pass for \c PredicateInfo.
struct PredicateInfoVerifierPass : PassInfoMixin<PredicateInfoVerifierPass> {
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
};
} // end namespace llvm
#endif // LLVM_TRANSFORMS_UTILS_PREDICATEINFO_H