llvm/llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombineInternal.h

//===- AggressiveInstCombineInternal.h --------------------------*- 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
//
//===----------------------------------------------------------------------===//
//
// This file implements the instruction pattern combiner classes.
// Currently, it handles pattern expressions for:
//  * Truncate instruction
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_LIB_TRANSFORMS_AGGRESSIVEINSTCOMBINE_COMBINEINTERNAL_H
#define LLVM_LIB_TRANSFORMS_AGGRESSIVEINSTCOMBINE_COMBINEINTERNAL_H

#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Support/KnownBits.h"

//===----------------------------------------------------------------------===//
// TruncInstCombine - looks for expression graphs dominated by trunc
// instructions and for each eligible graph, it will create a reduced bit-width
// expression and replace the old expression with this new one and remove the
// old one. Eligible expression graph is such that:
//   1. Contains only supported instructions.
//   2. Supported leaves: ZExtInst, SExtInst, TruncInst and Constant value.
//   3. Can be evaluated into type with reduced legal bit-width (or Trunc type).
//   4. All instructions in the graph must not have users outside the graph.
//      Only exception is for {ZExt, SExt}Inst with operand type equal to the
//      new reduced type chosen in (3).
//
// The motivation for this optimization is that evaluating and expression using
// smaller bit-width is preferable, especially for vectorization where we can
// fit more values in one vectorized instruction. In addition, this optimization
// may decrease the number of cast instructions, but will not increase it.
//===----------------------------------------------------------------------===//

namespace llvm {
class AssumptionCache;
class DataLayout;
class DominatorTree;
class Function;
class Instruction;
class TargetLibraryInfo;
class TruncInst;
class Type;
class Value;

class TruncInstCombine { … };
} // end namespace llvm.

#endif // LLVM_LIB_TRANSFORMS_AGGRESSIVEINSTCOMBINE_COMBINEINTERNAL_H