include/llvm/CodeGen/GlobalISel/CombinerHelper.h

   1 //===-- llvm/CodeGen/GlobalISel/CombinerHelper.h --------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===--------------------------------------------------------------------===//
   8 //
   9 /// This contains common combine transformations that may be used in a combine
  10 /// pass,or by the target elsewhere.
  11 /// Targets can pick individual opcode transformations from the helper or use
  12 /// tryCombine which invokes all transformations. All of the transformations
  13 /// return true if the MachineInstruction changed and false otherwise.
  14 //
  15 //===--------------------------------------------------------------------===//
  16
  17 #ifndef LLVM_CODEGEN_GLOBALISEL_COMBINER_HELPER_H
  18 #define LLVM_CODEGEN_GLOBALISEL_COMBINER_HELPER_H
  19
  20 #include "llvm/CodeGen/LowLevelType.h"
  21 #include "llvm/CodeGen/Register.h"
  22
  23 namespace llvm {
  24
  25 class GISelChangeObserver;
  26 class MachineIRBuilder;
  27 class MachineRegisterInfo;
  28 class MachineInstr;
  29 class MachineOperand;
  30 class GISelKnownBits;
  31 class MachineDominatorTree;
  32
  33 struct PreferredTuple {
  34   LLT Ty;                // The result type of the extend.
  35   unsigned ExtendOpcode; // G_ANYEXT/G_SEXT/G_ZEXT
  36   MachineInstr *MI;
  37 };
  38
  39 class CombinerHelper {
  40 protected:
  41   MachineIRBuilder &Builder;
  42   MachineRegisterInfo &MRI;
  43   GISelChangeObserver &Observer;
  44   GISelKnownBits *KB;
  45   MachineDominatorTree *MDT;
  46
  47 public:
  48   CombinerHelper(GISelChangeObserver &Observer, MachineIRBuilder &B,
  49                  GISelKnownBits *KB = nullptr,
  50                  MachineDominatorTree *MDT = nullptr);
  51
  52   /// MachineRegisterInfo::replaceRegWith() and inform the observer of the changes
  53   void replaceRegWith(MachineRegisterInfo &MRI, Register FromReg, Register ToReg) const;
  54
  55   /// Replace a single register operand with a new register and inform the
  56   /// observer of the changes.
  57   void replaceRegOpWith(MachineRegisterInfo &MRI, MachineOperand &FromRegOp,
  58                         Register ToReg) const;
  59
  60   /// If \p MI is COPY, try to combine it.
  61   /// Returns true if MI changed.
  62   bool tryCombineCopy(MachineInstr &MI);
  63   bool matchCombineCopy(MachineInstr &MI);
  64   void applyCombineCopy(MachineInstr &MI);
  65
  66   /// \brief \returns true if \p DefMI precedes \p UseMI or they are the same
  67   /// instruction. Both must be in the same basic block.
  68   bool isPredecessor(MachineInstr &DefMI, MachineInstr &UseMI);
  69
  70   /// \brief \returns true if \p DefMI dominates \p UseMI. By definition an
  71   /// instruction dominates itself.
  72   ///
  73   /// If we haven't been provided with a MachineDominatorTree during
  74   /// construction, this function returns a conservative result that tracks just
  75   /// a single basic block.
  76   bool dominates(MachineInstr &DefMI, MachineInstr &UseMI);
  77
  78   /// If \p MI is extend that consumes the result of a load, try to combine it.
  79   /// Returns true if MI changed.
  80   bool tryCombineExtendingLoads(MachineInstr &MI);
  81   bool matchCombineExtendingLoads(MachineInstr &MI, PreferredTuple &MatchInfo);
  82   void applyCombineExtendingLoads(MachineInstr &MI, PreferredTuple &MatchInfo);
  83
  84   /// Combine \p MI into a pre-indexed or post-indexed load/store operation if
  85   /// legal and the surrounding code makes it useful.
  86   bool tryCombineIndexedLoadStore(MachineInstr &MI);
  87
  88   bool matchCombineBr(MachineInstr &MI);
  89   bool tryCombineBr(MachineInstr &MI);
  90
  91   /// Optimize memcpy intrinsics et al, e.g. constant len calls.
  92   /// /p MaxLen if non-zero specifies the max length of a mem libcall to inline.
  93   ///
  94   /// For example (pre-indexed):
  95   ///
  96   ///     $addr = G_GEP $base, $offset
  97   ///     [...]
  98   ///     $val = G_LOAD $addr
  99   ///     [...]
 100   ///     $whatever = COPY $addr
 101   ///
 102   /// -->
 103   ///
 104   ///     $val, $addr = G_INDEXED_LOAD $base, $offset, 1 (IsPre)
 105   ///     [...]
 106   ///     $whatever = COPY $addr
 107   ///
 108   /// or (post-indexed):
 109   ///
 110   ///     G_STORE $val, $base
 111   ///     [...]
 112   ///     $addr = G_GEP $base, $offset
 113   ///     [...]
 114   ///     $whatever = COPY $addr
 115   ///
 116   /// -->
 117   ///
 118   ///     $addr = G_INDEXED_STORE $val, $base, $offset
 119   ///     [...]
 120   ///     $whatever = COPY $addr
 121   bool tryCombineMemCpyFamily(MachineInstr &MI, unsigned MaxLen = 0);
 122
 123   /// Try to transform \p MI by using all of the above
 124   /// combine functions. Returns true if changed.
 125   bool tryCombine(MachineInstr &MI);
 126
 127 private:
 128   // Memcpy family optimization helpers.
 129   bool optimizeMemcpy(MachineInstr &MI, Register Dst, Register Src,
 130                       unsigned KnownLen, unsigned DstAlign, unsigned SrcAlign,
 131                       bool IsVolatile);
 132   bool optimizeMemmove(MachineInstr &MI, Register Dst, Register Src,
 133                       unsigned KnownLen, unsigned DstAlign, unsigned SrcAlign,
 134                       bool IsVolatile);
 135   bool optimizeMemset(MachineInstr &MI, Register Dst, Register Val,
 136                       unsigned KnownLen, unsigned DstAlign, bool IsVolatile);
 137
 138   /// Given a non-indexed load or store instruction \p MI, find an offset that
 139   /// can be usefully and legally folded into it as a post-indexing operation.
 140   ///
 141   /// \returns true if a candidate is found.
 142   bool findPostIndexCandidate(MachineInstr &MI, Register &Addr, Register &Base,
 143                               Register &Offset);
 144
 145   /// Given a non-indexed load or store instruction \p MI, find an offset that
 146   /// can be usefully and legally folded into it as a pre-indexing operation.
 147   ///
 148   /// \returns true if a candidate is found.
 149   bool findPreIndexCandidate(MachineInstr &MI, Register &Addr, Register &Base,
 150                              Register &Offset);
 151 };
 152 } // namespace llvm
 153
 154 #endif