Yi Kong | 7bf2a68 | 2019-04-18 17:30:49 -0700 | [diff] [blame] | 1 | //===-- llvm/CodeGen/GlobalISel/CSEMIRBuilder.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 | /// \file |
| 9 | /// This file implements a version of MachineIRBuilder which CSEs insts within |
| 10 | /// a MachineBasicBlock. |
| 11 | //===----------------------------------------------------------------------===// |
| 12 | #ifndef LLVM_CODEGEN_GLOBALISEL_CSEMIRBUILDER_H |
| 13 | #define LLVM_CODEGEN_GLOBALISEL_CSEMIRBUILDER_H |
| 14 | |
| 15 | #include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h" |
| 16 | #include "llvm/CodeGen/GlobalISel/Utils.h" |
| 17 | |
| 18 | namespace llvm { |
| 19 | |
| 20 | /// Defines a builder that does CSE of MachineInstructions using GISelCSEInfo. |
| 21 | /// Eg usage. |
| 22 | /// |
| 23 | /// |
| 24 | /// GISelCSEInfo *Info = |
| 25 | /// &getAnalysis<GISelCSEAnalysisWrapperPass>().getCSEInfo(); CSEMIRBuilder |
| 26 | /// CB(Builder.getState()); CB.setCSEInfo(Info); auto A = CB.buildConstant(s32, |
| 27 | /// 42); auto B = CB.buildConstant(s32, 42); assert(A == B); unsigned CReg = |
| 28 | /// MRI.createGenericVirtualRegister(s32); auto C = CB.buildConstant(CReg, 42); |
| 29 | /// assert(C->getOpcode() == TargetOpcode::COPY); |
| 30 | /// Explicitly passing in a register would materialize a copy if possible. |
| 31 | /// CSEMIRBuilder also does trivial constant folding for binary ops. |
| 32 | class CSEMIRBuilder : public MachineIRBuilder { |
| 33 | |
| 34 | /// Returns true if A dominates B (within the same basic block). |
| 35 | /// Both iterators must be in the same basic block. |
| 36 | // |
| 37 | // TODO: Another approach for checking dominance is having two iterators and |
| 38 | // making them go towards each other until they meet or reach begin/end. Which |
| 39 | // approach is better? Should this even change dynamically? For G_CONSTANTS |
| 40 | // most of which will be at the top of the BB, the top down approach would be |
| 41 | // a better choice. Does IRTranslator placing constants at the beginning still |
| 42 | // make sense? Should this change based on Opcode? |
| 43 | bool dominates(MachineBasicBlock::const_iterator A, |
| 44 | MachineBasicBlock::const_iterator B) const; |
| 45 | |
| 46 | /// For given ID, find a machineinstr in the CSE Map. If found, check if it |
| 47 | /// dominates the current insertion point and if not, move it just before the |
| 48 | /// current insertion point and return it. If not found, return Null |
| 49 | /// MachineInstrBuilder. |
| 50 | MachineInstrBuilder getDominatingInstrForID(FoldingSetNodeID &ID, |
| 51 | void *&NodeInsertPos); |
| 52 | /// Simple check if we can CSE (we have the CSEInfo) or if this Opcode is |
| 53 | /// safe to CSE. |
| 54 | bool canPerformCSEForOpc(unsigned Opc) const; |
| 55 | |
| 56 | void profileDstOp(const DstOp &Op, GISelInstProfileBuilder &B) const; |
| 57 | |
| 58 | void profileDstOps(ArrayRef<DstOp> Ops, GISelInstProfileBuilder &B) const { |
| 59 | for (const DstOp &Op : Ops) |
| 60 | profileDstOp(Op, B); |
| 61 | } |
| 62 | |
| 63 | void profileSrcOp(const SrcOp &Op, GISelInstProfileBuilder &B) const; |
| 64 | |
| 65 | void profileSrcOps(ArrayRef<SrcOp> Ops, GISelInstProfileBuilder &B) const { |
| 66 | for (const SrcOp &Op : Ops) |
| 67 | profileSrcOp(Op, B); |
| 68 | } |
| 69 | |
| 70 | void profileMBBOpcode(GISelInstProfileBuilder &B, unsigned Opc) const; |
| 71 | |
| 72 | void profileEverything(unsigned Opc, ArrayRef<DstOp> DstOps, |
| 73 | ArrayRef<SrcOp> SrcOps, Optional<unsigned> Flags, |
| 74 | GISelInstProfileBuilder &B) const; |
| 75 | |
| 76 | // Takes a MachineInstrBuilder and inserts it into the CSEMap using the |
| 77 | // NodeInsertPos. |
| 78 | MachineInstrBuilder memoizeMI(MachineInstrBuilder MIB, void *NodeInsertPos); |
| 79 | |
| 80 | // If we have can CSE an instruction, but still need to materialize to a VReg, |
| 81 | // we emit a copy from the CSE'd inst to the VReg. |
| 82 | MachineInstrBuilder generateCopiesIfRequired(ArrayRef<DstOp> DstOps, |
| 83 | MachineInstrBuilder &MIB); |
| 84 | |
| 85 | // If we have can CSE an instruction, but still need to materialize to a VReg, |
| 86 | // check if we can generate copies. It's not possible to return a single MIB, |
| 87 | // while emitting copies to multiple vregs. |
| 88 | bool checkCopyToDefsPossible(ArrayRef<DstOp> DstOps); |
| 89 | |
| 90 | public: |
| 91 | // Pull in base class constructors. |
| 92 | using MachineIRBuilder::MachineIRBuilder; |
| 93 | // Unhide buildInstr |
| 94 | MachineInstrBuilder buildInstr(unsigned Opc, ArrayRef<DstOp> DstOps, |
| 95 | ArrayRef<SrcOp> SrcOps, |
| 96 | Optional<unsigned> Flag = None) override; |
| 97 | // Bring in the other overload from the base class. |
| 98 | using MachineIRBuilder::buildConstant; |
| 99 | |
| 100 | MachineInstrBuilder buildConstant(const DstOp &Res, |
| 101 | const ConstantInt &Val) override; |
| 102 | |
| 103 | // Bring in the other overload from the base class. |
| 104 | using MachineIRBuilder::buildFConstant; |
| 105 | MachineInstrBuilder buildFConstant(const DstOp &Res, |
| 106 | const ConstantFP &Val) override; |
| 107 | }; |
| 108 | } // namespace llvm |
| 109 | #endif |