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/MachineFunctionAnalysisManager.h"
22#include "llvm/CodeGen/MachinePassManager.h"
23#include "llvm/CodeGen/MachineRegisterInfo.h"
24#include "llvm/CodeGen/Passes.h"
25#include "llvm/IR/Analysis.h"
26#include "llvm/Support/Debug.h"
27#include "llvm/Support/raw_ostream.h"
28using namespace llvm;
29
30#define DEBUG_TYPE "wasm-reg-numbering"
31
32namespace {
33class WebAssemblyRegNumberingLegacy final : public MachineFunctionPass {
34 StringRef getPassName() const override {
35 return "WebAssembly Register Numbering";
36 }
37
38 void getAnalysisUsage(AnalysisUsage &AU) const override {
39 AU.setPreservesCFG();
40 MachineFunctionPass::getAnalysisUsage(AU);
41 }
42
43 bool runOnMachineFunction(MachineFunction &MF) override;
44
45public:
46 static char ID; // Pass identification, replacement for typeid
47 WebAssemblyRegNumberingLegacy() : MachineFunctionPass(ID) {}
48};
49} // end anonymous namespace
50
51char WebAssemblyRegNumberingLegacy::ID = 0;
52INITIALIZE_PASS(WebAssemblyRegNumberingLegacy, DEBUG_TYPE,
53 "Assigns WebAssembly register numbers for virtual registers",
54 false, false)
55
56FunctionPass *llvm::createWebAssemblyRegNumberingLegacyPass() {
57 return new WebAssemblyRegNumberingLegacy();
58}
59
60static bool regNumbering(MachineFunction &MF) {
61 LLVM_DEBUG(dbgs() << "********** Register Numbering **********\n"
62 "********** Function: "
63 << MF.getName() << '\n');
64
65 WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
66 MachineRegisterInfo &MRI = MF.getRegInfo();
67
68 MFI.initWARegs(MRI);
69
70 // WebAssembly argument registers are in the same index space as local
71 // variables. Assign the numbers for them first.
72 MachineBasicBlock &EntryMBB = MF.front();
73 for (MachineInstr &MI : EntryMBB) {
74 if (!WebAssembly::isArgument(Opc: MI.getOpcode()))
75 break;
76
77 int64_t Imm = MI.getOperand(i: 1).getImm();
78 LLVM_DEBUG(dbgs() << "Arg VReg " << printReg(MI.getOperand(0).getReg())
79 << " -> WAReg " << Imm << "\n");
80 MFI.setWAReg(VReg: MI.getOperand(i: 0).getReg(), WAReg: Imm);
81 }
82
83 // Then assign regular WebAssembly registers for all remaining used
84 // virtual registers. TODO: Consider sorting the registers by frequency of
85 // use, to maximize usage of small immediate fields.
86 unsigned NumVRegs = MF.getRegInfo().getNumVirtRegs();
87 unsigned NumStackRegs = 0;
88 // Start the numbering for locals after the arg regs
89 unsigned CurReg = MFI.getParams().size();
90 for (unsigned VRegIdx = 0; VRegIdx < NumVRegs; ++VRegIdx) {
91 Register VReg = Register::index2VirtReg(Index: VRegIdx);
92 // Skip unused registers.
93 if (MRI.use_empty(RegNo: VReg))
94 continue;
95 // Handle stackified registers.
96 if (MFI.isVRegStackified(VReg)) {
97 LLVM_DEBUG(dbgs() << "VReg " << printReg(VReg) << " -> WAReg "
98 << (INT32_MIN | NumStackRegs) << "\n");
99 MFI.setWAReg(VReg, INT32_MIN | NumStackRegs++);
100 continue;
101 }
102 if (MFI.getWAReg(VReg) == WebAssembly::UnusedReg) {
103 LLVM_DEBUG(dbgs() << "VReg " << printReg(VReg) << " -> WAReg " << CurReg
104 << "\n");
105 MFI.setWAReg(VReg, WAReg: CurReg++);
106 }
107 }
108
109 return true;
110}
111
112bool WebAssemblyRegNumberingLegacy::runOnMachineFunction(MachineFunction &MF) {
113 return regNumbering(MF);
114}
115
116PreservedAnalyses
117WebAssemblyRegNumberingPass::run(MachineFunction &MF,
118 MachineFunctionAnalysisManager &MFAM) {
119 return regNumbering(MF) ? getMachineFunctionPassPreservedAnalyses()
120 .preserveSet<CFGAnalyses>()
121 : PreservedAnalyses::all();
122}
123