1 //===-- WebAssemblyRegNumbering.cpp - Register Numbering ------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 /// This file implements a pass which assigns WebAssembly register
12 /// numbers for CodeGen virtual registers.
14 //===----------------------------------------------------------------------===//
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"
32 #define DEBUG_TYPE "wasm-reg-numbering"
35 class WebAssemblyRegNumbering final : public MachineFunctionPass {
36 StringRef getPassName() const override {
37 return "WebAssembly Register Numbering";
40 void getAnalysisUsage(AnalysisUsage &AU) const override {
42 MachineFunctionPass::getAnalysisUsage(AU);
45 bool runOnMachineFunction(MachineFunction &MF) override;
48 static char ID; // Pass identification, replacement for typeid
49 WebAssemblyRegNumbering() : MachineFunctionPass(ID) {}
51 } // end anonymous namespace
53 char WebAssemblyRegNumbering::ID = 0;
54 INITIALIZE_PASS(WebAssemblyRegNumbering, DEBUG_TYPE,
55 "Assigns WebAssembly register numbers for virtual registers",
58 FunctionPass *llvm::createWebAssemblyRegNumbering() {
59 return new WebAssemblyRegNumbering();
62 bool WebAssemblyRegNumbering::runOnMachineFunction(MachineFunction &MF) {
63 LLVM_DEBUG(dbgs() << "********** Register Numbering **********\n"
64 "********** Function: "
65 << MF.getName() << '\n');
67 WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
68 MachineRegisterInfo &MRI = MF.getRegInfo();
72 // WebAssembly argument registers are in the same index space as local
73 // variables. Assign the numbers for them first.
74 MachineBasicBlock &EntryMBB = MF.front();
75 for (MachineInstr &MI : EntryMBB) {
76 if (!WebAssembly::isArgument(MI))
79 int64_t Imm = MI.getOperand(1).getImm();
80 LLVM_DEBUG(dbgs() << "Arg VReg " << MI.getOperand(0).getReg()
81 << " -> WAReg " << Imm << "\n");
82 MFI.setWAReg(MI.getOperand(0).getReg(), Imm);
85 // Then assign regular WebAssembly registers for all remaining used
86 // virtual registers. TODO: Consider sorting the registers by frequency of
87 // use, to maximize usage of small immediate fields.
88 unsigned NumVRegs = MF.getRegInfo().getNumVirtRegs();
89 unsigned NumStackRegs = 0;
90 // Start the numbering for locals after the arg regs
91 unsigned CurReg = MFI.getParams().size();
92 for (unsigned VRegIdx = 0; VRegIdx < NumVRegs; ++VRegIdx) {
93 unsigned VReg = TargetRegisterInfo::index2VirtReg(VRegIdx);
94 // Skip unused registers.
95 if (MRI.use_empty(VReg))
97 // Handle stackified registers.
98 if (MFI.isVRegStackified(VReg)) {
99 LLVM_DEBUG(dbgs() << "VReg " << VReg << " -> WAReg "
100 << (INT32_MIN | NumStackRegs) << "\n");
101 MFI.setWAReg(VReg, INT32_MIN | NumStackRegs++);
104 if (MFI.getWAReg(VReg) == WebAssemblyFunctionInfo::UnusedReg) {
105 LLVM_DEBUG(dbgs() << "VReg " << VReg << " -> WAReg " << CurReg << "\n");
106 MFI.setWAReg(VReg, CurReg++);