WebAssemblyRegNumbering.cpp revision 321369
1//===-- WebAssemblyRegNumbering.cpp - Register Numbering ------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9/// 10/// \file 11/// \brief This file implements a pass which assigns WebAssembly register 12/// numbers for CodeGen virtual registers. 13/// 14//===----------------------------------------------------------------------===// 15 16#include "MCTargetDesc/WebAssemblyMCTargetDesc.h" 17#include "WebAssembly.h" 18#include "WebAssemblyMachineFunctionInfo.h" 19#include "WebAssemblySubtarget.h" 20#include "WebAssemblyUtilities.h" 21#include "llvm/ADT/SCCIterator.h" 22#include "llvm/CodeGen/MachineFrameInfo.h" 23#include "llvm/CodeGen/MachineFunction.h" 24#include "llvm/CodeGen/MachineInstrBuilder.h" 25#include "llvm/CodeGen/MachineLoopInfo.h" 26#include "llvm/CodeGen/MachineRegisterInfo.h" 27#include "llvm/CodeGen/Passes.h" 28#include "llvm/Support/Debug.h" 29#include "llvm/Support/raw_ostream.h" 30using namespace llvm; 31 32#define DEBUG_TYPE "wasm-reg-numbering" 33 34namespace { 35class WebAssemblyRegNumbering final : public MachineFunctionPass { 36 StringRef getPassName() const override { 37 return "WebAssembly Register Numbering"; 38 } 39 40 void getAnalysisUsage(AnalysisUsage &AU) const override { 41 AU.setPreservesCFG(); 42 MachineFunctionPass::getAnalysisUsage(AU); 43 } 44 45 bool runOnMachineFunction(MachineFunction &MF) override; 46 47public: 48 static char ID; // Pass identification, replacement for typeid 49 WebAssemblyRegNumbering() : MachineFunctionPass(ID) {} 50}; 51} // end anonymous namespace 52 53char WebAssemblyRegNumbering::ID = 0; 54FunctionPass *llvm::createWebAssemblyRegNumbering() { 55 return new WebAssemblyRegNumbering(); 56} 57 58bool WebAssemblyRegNumbering::runOnMachineFunction(MachineFunction &MF) { 59 DEBUG(dbgs() << "********** Register Numbering **********\n" 60 "********** Function: " 61 << MF.getName() << '\n'); 62 63 WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>(); 64 MachineRegisterInfo &MRI = MF.getRegInfo(); 65 66 MFI.initWARegs(); 67 68 // WebAssembly argument registers are in the same index space as local 69 // variables. Assign the numbers for them first. 70 MachineBasicBlock &EntryMBB = MF.front(); 71 for (MachineInstr &MI : EntryMBB) { 72 if (!WebAssembly::isArgument(MI)) 73 break; 74 75 int64_t Imm = MI.getOperand(1).getImm(); 76 DEBUG(dbgs() << "Arg VReg " << MI.getOperand(0).getReg() << " -> WAReg " 77 << Imm << "\n"); 78 MFI.setWAReg(MI.getOperand(0).getReg(), Imm); 79 } 80 81 // Then assign regular WebAssembly registers for all remaining used 82 // virtual registers. TODO: Consider sorting the registers by frequency of 83 // use, to maximize usage of small immediate fields. 84 unsigned NumVRegs = MF.getRegInfo().getNumVirtRegs(); 85 unsigned NumStackRegs = 0; 86 // Start the numbering for locals after the arg regs 87 unsigned CurReg = MFI.getParams().size(); 88 for (unsigned VRegIdx = 0; VRegIdx < NumVRegs; ++VRegIdx) { 89 unsigned VReg = TargetRegisterInfo::index2VirtReg(VRegIdx); 90 // Skip unused registers. 91 if (MRI.use_empty(VReg)) 92 continue; 93 // Handle stackified registers. 94 if (MFI.isVRegStackified(VReg)) { 95 DEBUG(dbgs() << "VReg " << VReg << " -> WAReg " 96 << (INT32_MIN | NumStackRegs) << "\n"); 97 MFI.setWAReg(VReg, INT32_MIN | NumStackRegs++); 98 continue; 99 } 100 if (MFI.getWAReg(VReg) == WebAssemblyFunctionInfo::UnusedReg) { 101 DEBUG(dbgs() << "VReg " << VReg << " -> WAReg " << CurReg << "\n"); 102 MFI.setWAReg(VReg, CurReg++); 103 } 104 } 105 106 return true; 107} 108