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 "WebAssembly.h"
17 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
18 #include "WebAssemblyMachineFunctionInfo.h"
19 #include "WebAssemblySubtarget.h"
20 #include "llvm/ADT/SCCIterator.h"
21 #include "llvm/CodeGen/MachineFunction.h"
22 #include "llvm/CodeGen/MachineInstrBuilder.h"
23 #include "llvm/CodeGen/MachineLoopInfo.h"
24 #include "llvm/CodeGen/MachineRegisterInfo.h"
25 #include "llvm/CodeGen/Passes.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/raw_ostream.h"
28 using namespace llvm;
29 
30 #define DEBUG_TYPE "wasm-reg-numbering"
31 
32 namespace {
33 class WebAssemblyRegNumbering final : public MachineFunctionPass {
34   const char *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 
45 public:
46   static char ID; // Pass identification, replacement for typeid
47   WebAssemblyRegNumbering() : MachineFunctionPass(ID) {}
48 };
49 } // end anonymous namespace
50 
51 char WebAssemblyRegNumbering::ID = 0;
52 FunctionPass *llvm::createWebAssemblyRegNumbering() {
53   return new WebAssemblyRegNumbering();
54 }
55 
56 bool WebAssemblyRegNumbering::runOnMachineFunction(MachineFunction &MF) {
57   DEBUG(dbgs() << "********** Register Numbering **********\n"
58                   "********** Function: "
59                << MF.getName() << '\n');
60 
61   WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
62   MachineRegisterInfo &MRI = MF.getRegInfo();
63 
64   MFI.initWARegs();
65 
66   // WebAssembly argument registers are in the same index space as local
67   // variables. Assign the numbers for them first.
68   MachineBasicBlock &EntryMBB = MF.front();
69   for (MachineInstr &MI : EntryMBB) {
70     switch (MI.getOpcode()) {
71     case WebAssembly::ARGUMENT_I32:
72     case WebAssembly::ARGUMENT_I64:
73     case WebAssembly::ARGUMENT_F32:
74     case WebAssembly::ARGUMENT_F64:
75       MFI.setWAReg(MI.getOperand(0).getReg(), MI.getOperand(1).getImm());
76       break;
77     default:
78       break;
79     }
80   }
81 
82   // Then assign regular WebAssembly registers for all remaining used
83   // virtual registers.
84   unsigned NumArgRegs = MFI.getParams().size();
85   unsigned NumVRegs = MF.getRegInfo().getNumVirtRegs();
86   unsigned NumStackRegs = 0;
87   unsigned CurReg = 0;
88   for (unsigned VRegIdx = 0; VRegIdx < NumVRegs; ++VRegIdx) {
89     unsigned VReg = TargetRegisterInfo::index2VirtReg(VRegIdx);
90     // Handle stackified registers.
91     if (MFI.isVRegStackified(VReg)) {
92       MFI.setWAReg(VReg, INT32_MIN | NumStackRegs++);
93       continue;
94     }
95     // Skip unused registers.
96     if (MRI.use_empty(VReg))
97       continue;
98     if (MFI.getWAReg(VReg) == WebAssemblyFunctionInfo::UnusedReg)
99       MFI.setWAReg(VReg, NumArgRegs + CurReg++);
100   }
101 
102   return true;
103 }
104