llvm/llvm/include/llvm/Transforms/Utils/PredicateInfo.h

//===- 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"

namespace llvm {

class AssumptionCache;
class DominatorTree;
class Function;
class Value;
class IntrinsicInst;
class raw_ostream;

enum PredicateType { … };

/// 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 { … };

// Base class for all predicate information we provide.
// All of our predicate information has at least a comparison.
class PredicateBase : public ilist_node<PredicateBase> { … };

// 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 { … };

// 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 { … };

// Provides predicate information for branches.
class PredicateBranch : public PredicateWithEdge { … };

class PredicateSwitch : public PredicateWithEdge { … };

/// Encapsulates PredicateInfo, including all data associated with memory
/// accesses.
class PredicateInfo { … };

/// Printer pass for \c PredicateInfo.
class PredicateInfoPrinterPass
    : public PassInfoMixin<PredicateInfoPrinterPass> { … };

/// Verifier pass for \c PredicateInfo.
struct PredicateInfoVerifierPass : PassInfoMixin<PredicateInfoVerifierPass> { … };

} // end namespace llvm

#endif // LLVM_TRANSFORMS_UTILS_PREDICATEINFO_H