SelectionDAGAddressAnalysis.h

Go to the documentation of this file.

//===- SelectionDAGAddressAnalysis.h - DAG Address Analysis -----*- 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
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_CODEGEN_SELECTIONDAGADDRESSANALYSIS_H
#define LLVM_CODEGEN_SELECTIONDAGADDRESSANALYSIS_H
 
#include "llvm/Analysis/MemoryLocation.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/TypeSize.h"
#include <cstdint>
 
namespace llvm {
 
class SelectionDAG;
 
/// Helper struct to parse and store a memory address as base + index + offset.
/// We ignore sign extensions when it is safe to do so.
/// The following two expressions are not equivalent. To differentiate we need
/// to store whether there was a sign extension involved in the index
/// computation.
///  (load (i64 add (i64 copyfromreg %c)
///                 (i64 signextend (add (i8 load %index)
///                                      (i8 1))))
/// vs
///
/// (load (i64 add (i64 copyfromreg %c)
///                (i64 signextend (i32 add (i32 signextend (i8 load %index))
///                                         (i32 1)))))
class BaseIndexOffset {
private:
  SDValue Base;
  SDValue Index;
  std::optional<StackOffset> Offset;
  bool IsIndexSignExt = false;
 
public:
  BaseIndexOffset() = default;
  BaseIndexOffset(SDValue Base, SDValue Index, bool IsIndexSignExt)
      : Base(Base), Index(Index), IsIndexSignExt(IsIndexSignExt) {}
  BaseIndexOffset(SDValue Base, SDValue Index, int64_t Offset,
                  bool IsIndexSignExt)
      : BaseIndexOffset(Base, Index, StackOffset::getFixed(Offset),
                        IsIndexSignExt) {}
  BaseIndexOffset(SDValue Base, SDValue Index, StackOffset Offset,
                  bool IsIndexSignExt)
      : Base(Base), Index(Index), Offset(Offset),
        IsIndexSignExt(IsIndexSignExt) {}
 
  SDValue getBase() { return Base; }
  SDValue getBase() const { return Base; }
  SDValue getIndex() { return Index; }
  SDValue getIndex() const { return Index; }
  void addToOffset(int64_t VectorOff) {
    Offset = Offset.value_or(StackOffset::getFixed(0)) +
             StackOffset::getFixed(VectorOff);
  }
  // Whether the parsed offset has only a fixed component.
  bool hasValidOffset() const { return Offset && Offset->getScalable() == 0; }
  // Whether a fixed or scalable offset was parsed.
  bool hasValidStackOffset() const { return Offset.has_value(); }
  int64_t getOffset() const {
    assert(hasValidOffset() && "Expected a fixed offset");
    return Offset->getFixed();
  }
 
  // Returns true if `Other` and `*this` are both some offset from the same base
  // pointer. In that case, `Off` is set to the offset between `*this` and
  // `Other` (negative if `Other` is before `*this`).
  LLVM_ABI bool equalBaseIndex(const BaseIndexOffset &Other,
                               const SelectionDAG &DAG, StackOffset &Off) const;
 
  // Like the above, but also allows a known fixed offset between the pointers.
  LLVM_ABI bool equalBaseIndex(const BaseIndexOffset &Other,
                               const SelectionDAG &DAG, int64_t &Off) const;
 
  bool equalBaseIndex(const BaseIndexOffset &Other,
                      const SelectionDAG &DAG) const {
    StackOffset Off;
    return equalBaseIndex(Other, DAG, Off);
  }
 
  // Returns true if `Other` (with size `OtherSize`) can be proven to be fully
  // contained in `*this` (with size `Size`).
  LLVM_ABI bool contains(const SelectionDAG &DAG, int64_t BitSize,
                         const BaseIndexOffset &Other, int64_t OtherBitSize,
                         int64_t &BitOffset) const;
 
  bool contains(const SelectionDAG &DAG, int64_t BitSize,
                const BaseIndexOffset &Other, int64_t OtherBitSize) const {
    int64_t BitOffset;
    return contains(DAG, BitSize, Other, OtherBitSize, BitOffset);
  }
 
  // Returns true `Op0` and `Op1` can be proven to alias/not alias, in
  // which case `IsAlias` is set to true/false.
  LLVM_ABI static bool computeAliasing(const SDNode *Op0,
                                       const LocationSize NumBytes0,
                                       const SDNode *Op1,
                                       const LocationSize NumBytes1,
                                       const SelectionDAG &DAG, bool &IsAlias);
 
  /// Parses tree in N for base, index, and fixed/scalable offsets.
  LLVM_ABI static BaseIndexOffset match(const SDNode *N,
                                        const SelectionDAG &DAG);
 
  LLVM_ABI void print(raw_ostream &OS) const;
  LLVM_ABI void dump() const;
};
 
} // end namespace llvm
 
#endif // LLVM_CODEGEN_SELECTIONDAGADDRESSANALYSIS_H