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 "WebAssemblySubtarget.h"
19 #include "WebAssemblyUtilities.h"
20 #include "llvm/ADT/SCCIterator.h"
21 #include "llvm/CodeGen/MachineFrameInfo.h"
22 #include "llvm/CodeGen/MachineFunction.h"
23 #include "llvm/CodeGen/MachineInstrBuilder.h"
24 #include "llvm/CodeGen/MachineLoopInfo.h"
25 #include "llvm/CodeGen/MachineRegisterInfo.h"
26 #include "llvm/CodeGen/Passes.h"
27 #include "llvm/Support/Debug.h"
28 #include "llvm/Support/raw_ostream.h"
29 using namespace llvm;
30
31 #define DEBUG_TYPE "wasm-reg-numbering"
32
33 namespace {
34 class WebAssemblyRegNumbering final : public MachineFunctionPass {
getPassName() const35 StringRef getPassName() const override {
36 return "WebAssembly Register Numbering";
37 }
38
getAnalysisUsage(AnalysisUsage & AU) const39 void getAnalysisUsage(AnalysisUsage &AU) const override {
40 AU.setPreservesCFG();
41 MachineFunctionPass::getAnalysisUsage(AU);
42 }
43
44 bool runOnMachineFunction(MachineFunction &MF) override;
45
46 public:
47 static char ID; // Pass identification, replacement for typeid
WebAssemblyRegNumbering()48 WebAssemblyRegNumbering() : MachineFunctionPass(ID) {}
49 };
50 } // end anonymous namespace
51
52 char WebAssemblyRegNumbering::ID = 0;
53 INITIALIZE_PASS(WebAssemblyRegNumbering, DEBUG_TYPE,
54 "Assigns WebAssembly register numbers for virtual registers",
55 false, false)
56
createWebAssemblyRegNumbering()57 FunctionPass *llvm::createWebAssemblyRegNumbering() {
58 return new WebAssemblyRegNumbering();
59 }
60
runOnMachineFunction(MachineFunction & MF)61 bool WebAssemblyRegNumbering::runOnMachineFunction(MachineFunction &MF) {
62 LLVM_DEBUG(dbgs() << "********** Register Numbering **********\n"
63 "********** Function: "
64 << MF.getName() << '\n');
65
66 WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
67 MachineRegisterInfo &MRI = MF.getRegInfo();
68
69 MFI.initWARegs();
70
71 // WebAssembly argument registers are in the same index space as local
72 // variables. Assign the numbers for them first.
73 MachineBasicBlock &EntryMBB = MF.front();
74 for (MachineInstr &MI : EntryMBB) {
75 if (!WebAssembly::isArgument(MI.getOpcode()))
76 break;
77
78 int64_t Imm = MI.getOperand(1).getImm();
79 LLVM_DEBUG(dbgs() << "Arg VReg " << MI.getOperand(0).getReg()
80 << " -> WAReg " << Imm << "\n");
81 MFI.setWAReg(MI.getOperand(0).getReg(), Imm);
82 }
83
84 // Then assign regular WebAssembly registers for all remaining used
85 // virtual registers. TODO: Consider sorting the registers by frequency of
86 // use, to maximize usage of small immediate fields.
87 unsigned NumVRegs = MF.getRegInfo().getNumVirtRegs();
88 unsigned NumStackRegs = 0;
89 // Start the numbering for locals after the arg regs
90 unsigned CurReg = MFI.getParams().size();
91 for (unsigned VRegIdx = 0; VRegIdx < NumVRegs; ++VRegIdx) {
92 unsigned VReg = Register::index2VirtReg(VRegIdx);
93 // Skip unused registers.
94 if (MRI.use_empty(VReg))
95 continue;
96 // Handle stackified registers.
97 if (MFI.isVRegStackified(VReg)) {
98 LLVM_DEBUG(dbgs() << "VReg " << VReg << " -> WAReg "
99 << (INT32_MIN | NumStackRegs) << "\n");
100 MFI.setWAReg(VReg, INT32_MIN | NumStackRegs++);
101 continue;
102 }
103 if (MFI.getWAReg(VReg) == WebAssemblyFunctionInfo::UnusedReg) {
104 LLVM_DEBUG(dbgs() << "VReg " << VReg << " -> WAReg " << CurReg << "\n");
105 MFI.setWAReg(VReg, CurReg++);
106 }
107 }
108
109 return true;
110 }
111