lib/Target/WebAssembly/WebAssemblyInstrInfo.cpp

   1 //===-- WebAssemblyInstrInfo.cpp - WebAssembly Instruction Information ----===//
   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 /// \file
  10 /// This file contains the WebAssembly implementation of the
  11 /// TargetInstrInfo class.
  12 ///
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "WebAssemblyInstrInfo.h"
  16 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
  17 #include "WebAssemblyMachineFunctionInfo.h"
  18 #include "WebAssemblySubtarget.h"
  19 #include "llvm/CodeGen/MachineFrameInfo.h"
  20 #include "llvm/CodeGen/MachineInstrBuilder.h"
  21 #include "llvm/CodeGen/MachineMemOperand.h"
  22 #include "llvm/CodeGen/MachineRegisterInfo.h"
  23 using namespace llvm;
  24
  25 #define DEBUG_TYPE "wasm-instr-info"
  26
  27 #define GET_INSTRINFO_CTOR_DTOR
  28 #include "WebAssemblyGenInstrInfo.inc"
  29
  30 // defines WebAssembly::getNamedOperandIdx
  31 #define GET_INSTRINFO_NAMED_OPS
  32 #include "WebAssemblyGenInstrInfo.inc"
  33
  34 WebAssemblyInstrInfo::WebAssemblyInstrInfo(const WebAssemblySubtarget &STI)
  35     : WebAssemblyGenInstrInfo(WebAssembly::ADJCALLSTACKDOWN,
  36                               WebAssembly::ADJCALLSTACKUP,
  37                               WebAssembly::CATCHRET),
  38       RI(STI.getTargetTriple()) {}
  39
  40 bool WebAssemblyInstrInfo::isReallyTriviallyReMaterializable(
  41     const MachineInstr &MI, AAResults *AA) const {
  42   switch (MI.getOpcode()) {
  43   case WebAssembly::CONST_I32:
  44   case WebAssembly::CONST_I64:
  45   case WebAssembly::CONST_F32:
  46   case WebAssembly::CONST_F64:
  47     // isReallyTriviallyReMaterializableGeneric misses these because of the
  48     // ARGUMENTS implicit def, so we manualy override it here.
  49     return true;
  50   default:
  51     return false;
  52   }
  53 }
  54
  55 void WebAssemblyInstrInfo::copyPhysReg(MachineBasicBlock &MBB,
  56                                        MachineBasicBlock::iterator I,
  57                                        const DebugLoc &DL, unsigned DestReg,
  58                                        unsigned SrcReg, bool KillSrc) const {
  59   // This method is called by post-RA expansion, which expects only pregs to
  60   // exist. However we need to handle both here.
  61   auto &MRI = MBB.getParent()->getRegInfo();
  62   const TargetRegisterClass *RC =
  63       Register::isVirtualRegister(DestReg)
  64           ? MRI.getRegClass(DestReg)
  65           : MRI.getTargetRegisterInfo()->getMinimalPhysRegClass(DestReg);
  66
  67   unsigned CopyOpcode;
  68   if (RC == &WebAssembly::I32RegClass)
  69     CopyOpcode = WebAssembly::COPY_I32;
  70   else if (RC == &WebAssembly::I64RegClass)
  71     CopyOpcode = WebAssembly::COPY_I64;
  72   else if (RC == &WebAssembly::F32RegClass)
  73     CopyOpcode = WebAssembly::COPY_F32;
  74   else if (RC == &WebAssembly::F64RegClass)
  75     CopyOpcode = WebAssembly::COPY_F64;
  76   else if (RC == &WebAssembly::V128RegClass)
  77     CopyOpcode = WebAssembly::COPY_V128;
  78   else if (RC == &WebAssembly::EXNREFRegClass)
  79     CopyOpcode = WebAssembly::COPY_EXNREF;
  80   else
  81     llvm_unreachable("Unexpected register class");
  82
  83   BuildMI(MBB, I, DL, get(CopyOpcode), DestReg)
  84       .addReg(SrcReg, KillSrc ? RegState::Kill : 0);
  85 }
  86
  87 MachineInstr *WebAssemblyInstrInfo::commuteInstructionImpl(
  88     MachineInstr &MI, bool NewMI, unsigned OpIdx1, unsigned OpIdx2) const {
  89   // If the operands are stackified, we can't reorder them.
  90   WebAssemblyFunctionInfo &MFI =
  91       *MI.getParent()->getParent()->getInfo<WebAssemblyFunctionInfo>();
  92   if (MFI.isVRegStackified(MI.getOperand(OpIdx1).getReg()) ||
  93       MFI.isVRegStackified(MI.getOperand(OpIdx2).getReg()))
  94     return nullptr;
  95
  96   // Otherwise use the default implementation.
  97   return TargetInstrInfo::commuteInstructionImpl(MI, NewMI, OpIdx1, OpIdx2);
  98 }
  99
 100 // Branch analysis.
 101 bool WebAssemblyInstrInfo::analyzeBranch(MachineBasicBlock &MBB,
 102                                          MachineBasicBlock *&TBB,
 103                                          MachineBasicBlock *&FBB,
 104                                          SmallVectorImpl<MachineOperand> &Cond,
 105                                          bool /*AllowModify*/) const {
 106   const auto &MFI = *MBB.getParent()->getInfo<WebAssemblyFunctionInfo>();
 107   // WebAssembly has control flow that doesn't have explicit branches or direct
 108   // fallthrough (e.g. try/catch), which can't be modeled by analyzeBranch. It
 109   // is created after CFGStackify.
 110   if (MFI.isCFGStackified())
 111     return true;
 112
 113   bool HaveCond = false;
 114   for (MachineInstr &MI : MBB.terminators()) {
 115     switch (MI.getOpcode()) {
 116     default:
 117       // Unhandled instruction; bail out.
 118       return true;
 119     case WebAssembly::BR_IF:
 120       if (HaveCond)
 121         return true;
 122       Cond.push_back(MachineOperand::CreateImm(true));
 123       Cond.push_back(MI.getOperand(1));
 124       TBB = MI.getOperand(0).getMBB();
 125       HaveCond = true;
 126       break;
 127     case WebAssembly::BR_UNLESS:
 128       if (HaveCond)
 129         return true;
 130       Cond.push_back(MachineOperand::CreateImm(false));
 131       Cond.push_back(MI.getOperand(1));
 132       TBB = MI.getOperand(0).getMBB();
 133       HaveCond = true;
 134       break;
 135     case WebAssembly::BR:
 136       if (!HaveCond)
 137         TBB = MI.getOperand(0).getMBB();
 138       else
 139         FBB = MI.getOperand(0).getMBB();
 140       break;
 141     case WebAssembly::BR_ON_EXN:
 142       if (HaveCond)
 143         return true;
 144       Cond.push_back(MachineOperand::CreateImm(true));
 145       Cond.push_back(MI.getOperand(2));
 146       TBB = MI.getOperand(0).getMBB();
 147       HaveCond = true;
 148       break;
 149     }
 150     if (MI.isBarrier())
 151       break;
 152   }
 153
 154   return false;
 155 }
 156
 157 unsigned WebAssemblyInstrInfo::removeBranch(MachineBasicBlock &MBB,
 158                                             int *BytesRemoved) const {
 159   assert(!BytesRemoved && "code size not handled");
 160
 161   MachineBasicBlock::instr_iterator I = MBB.instr_end();
 162   unsigned Count = 0;
 163
 164   while (I != MBB.instr_begin()) {
 165     --I;
 166     if (I->isDebugInstr())
 167       continue;
 168     if (!I->isTerminator())
 169       break;
 170     // Remove the branch.
 171     I->eraseFromParent();
 172     I = MBB.instr_end();
 173     ++Count;
 174   }
 175
 176   return Count;
 177 }
 178
 179 unsigned WebAssemblyInstrInfo::insertBranch(
 180     MachineBasicBlock &MBB, MachineBasicBlock *TBB, MachineBasicBlock *FBB,
 181     ArrayRef<MachineOperand> Cond, const DebugLoc &DL, int *BytesAdded) const {
 182   assert(!BytesAdded && "code size not handled");
 183
 184   if (Cond.empty()) {
 185     if (!TBB)
 186       return 0;
 187
 188     BuildMI(&MBB, DL, get(WebAssembly::BR)).addMBB(TBB);
 189     return 1;
 190   }
 191
 192   assert(Cond.size() == 2 && "Expected a flag and a successor block");
 193
 194   MachineFunction &MF = *MBB.getParent();
 195   auto &MRI = MF.getRegInfo();
 196   bool IsBrOnExn = Cond[1].isReg() && MRI.getRegClass(Cond[1].getReg()) ==
 197                                           &WebAssembly::EXNREFRegClass;
 198
 199   if (Cond[0].getImm()) {
 200     if (IsBrOnExn) {
 201       const char *CPPExnSymbol = MF.createExternalSymbolName("__cpp_exception");
 202       BuildMI(&MBB, DL, get(WebAssembly::BR_ON_EXN))
 203           .addMBB(TBB)
 204           .addExternalSymbol(CPPExnSymbol)
 205           .add(Cond[1]);
 206     } else
 207       BuildMI(&MBB, DL, get(WebAssembly::BR_IF)).addMBB(TBB).add(Cond[1]);
 208   } else {
 209     assert(!IsBrOnExn && "br_on_exn does not have a reversed condition");
 210     BuildMI(&MBB, DL, get(WebAssembly::BR_UNLESS)).addMBB(TBB).add(Cond[1]);
 211   }
 212   if (!FBB)
 213     return 1;
 214
 215   BuildMI(&MBB, DL, get(WebAssembly::BR)).addMBB(FBB);
 216   return 2;
 217 }
 218
 219 bool WebAssemblyInstrInfo::reverseBranchCondition(
 220     SmallVectorImpl<MachineOperand> &Cond) const {
 221   assert(Cond.size() == 2 && "Expected a flag and a condition expression");
 222
 223   // br_on_exn's condition cannot be reversed
 224   MachineFunction &MF = *Cond[1].getParent()->getParent()->getParent();
 225   auto &MRI = MF.getRegInfo();
 226   if (Cond[1].isReg() &&
 227       MRI.getRegClass(Cond[1].getReg()) == &WebAssembly::EXNREFRegClass)
 228     return true;
 229
 230   Cond.front() = MachineOperand::CreateImm(!Cond.front().getImm());
 231   return false;
 232 }