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