WebAssemblyAsmPrinter.cpp revision 292915 
1//===-- WebAssemblyAsmPrinter.cpp - WebAssembly LLVM assembly writer ------===//
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 contains a printer that converts from our internal
12/// representation of machine-dependent LLVM code to the WebAssembly assembly
13/// language.
14///
15//===----------------------------------------------------------------------===//
16
17#include "WebAssembly.h"
18#include "InstPrinter/WebAssemblyInstPrinter.h"
19#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
20#include "WebAssemblyMCInstLower.h"
21#include "WebAssemblyMachineFunctionInfo.h"
22#include "WebAssemblyRegisterInfo.h"
23#include "WebAssemblySubtarget.h"
24#include "llvm/ADT/StringExtras.h"
25#include "llvm/CodeGen/Analysis.h"
26#include "llvm/CodeGen/AsmPrinter.h"
27#include "llvm/CodeGen/MachineConstantPool.h"
28#include "llvm/CodeGen/MachineInstr.h"
29#include "llvm/IR/DataLayout.h"
30#include "llvm/MC/MCContext.h"
31#include "llvm/MC/MCStreamer.h"
32#include "llvm/MC/MCSymbol.h"
33#include "llvm/Support/Debug.h"
34#include "llvm/Support/TargetRegistry.h"
35#include "llvm/Support/raw_ostream.h"
36using namespace llvm;
37
38#define DEBUG_TYPE "asm-printer"
39
40namespace {
41
42class WebAssemblyAsmPrinter final : public AsmPrinter {
43  const MachineRegisterInfo *MRI;
44  const WebAssemblyFunctionInfo *MFI;
45
46public:
47  WebAssemblyAsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer)
48      : AsmPrinter(TM, std::move(Streamer)), MRI(nullptr), MFI(nullptr) {}
49
50private:
51  const char *getPassName() const override {
52    return "WebAssembly Assembly Printer";
53  }
54
55  //===------------------------------------------------------------------===//
56  // MachineFunctionPass Implementation.
57  //===------------------------------------------------------------------===//
58
59  bool runOnMachineFunction(MachineFunction &MF) override {
60    MRI = &MF.getRegInfo();
61    MFI = MF.getInfo<WebAssemblyFunctionInfo>();
62    return AsmPrinter::runOnMachineFunction(MF);
63  }
64
65  //===------------------------------------------------------------------===//
66  // AsmPrinter Implementation.
67  //===------------------------------------------------------------------===//
68
69  void EmitJumpTableInfo() override;
70  void EmitConstantPool() override;
71  void EmitFunctionBodyStart() override;
72  void EmitInstruction(const MachineInstr *MI) override;
73  bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
74                       unsigned AsmVariant, const char *ExtraCode,
75                       raw_ostream &OS) override;
76  bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
77                             unsigned AsmVariant, const char *ExtraCode,
78                             raw_ostream &OS) override;
79
80  MVT getRegType(unsigned RegNo) const;
81  const char *toString(MVT VT) const;
82  std::string regToString(const MachineOperand &MO);
83};
84
85} // end anonymous namespace
86
87//===----------------------------------------------------------------------===//
88// Helpers.
89//===----------------------------------------------------------------------===//
90
91MVT WebAssemblyAsmPrinter::getRegType(unsigned RegNo) const {
92  const TargetRegisterClass *TRC =
93      TargetRegisterInfo::isVirtualRegister(RegNo) ?
94      MRI->getRegClass(RegNo) :
95      MRI->getTargetRegisterInfo()->getMinimalPhysRegClass(RegNo);
96  for (MVT T : {MVT::i32, MVT::i64, MVT::f32, MVT::f64})
97    if (TRC->hasType(T))
98      return T;
99  DEBUG(errs() << "Unknown type for register number: " << RegNo);
100  llvm_unreachable("Unknown register type");
101  return MVT::Other;
102}
103
104std::string WebAssemblyAsmPrinter::regToString(const MachineOperand &MO) {
105  unsigned RegNo = MO.getReg();
106  assert(TargetRegisterInfo::isVirtualRegister(RegNo) &&
107         "Unlowered physical register encountered during assembly printing");
108  assert(!MFI->isVRegStackified(RegNo));
109  unsigned WAReg = MFI->getWAReg(RegNo);
110  assert(WAReg != WebAssemblyFunctionInfo::UnusedReg);
111  return '$' + utostr(WAReg);
112}
113
114const char *WebAssemblyAsmPrinter::toString(MVT VT) const {
115  return WebAssembly::TypeToString(VT);
116}
117
118//===----------------------------------------------------------------------===//
119// WebAssemblyAsmPrinter Implementation.
120//===----------------------------------------------------------------------===//
121
122void WebAssemblyAsmPrinter::EmitConstantPool() {
123  assert(MF->getConstantPool()->getConstants().empty() &&
124         "WebAssembly disables constant pools");
125}
126
127void WebAssemblyAsmPrinter::EmitJumpTableInfo() {
128  // Nothing to do; jump tables are incorporated into the instruction stream.
129}
130
131static void ComputeLegalValueVTs(const Function &F, const TargetMachine &TM,
132                                 Type *Ty, SmallVectorImpl<MVT> &ValueVTs) {
133  const DataLayout &DL(F.getParent()->getDataLayout());
134  const WebAssemblyTargetLowering &TLI =
135      *TM.getSubtarget<WebAssemblySubtarget>(F).getTargetLowering();
136  SmallVector<EVT, 4> VTs;
137  ComputeValueVTs(TLI, DL, Ty, VTs);
138
139  for (EVT VT : VTs) {
140    unsigned NumRegs = TLI.getNumRegisters(F.getContext(), VT);
141    MVT RegisterVT = TLI.getRegisterType(F.getContext(), VT);
142    for (unsigned i = 0; i != NumRegs; ++i)
143      ValueVTs.push_back(RegisterVT);
144  }
145}
146
147void WebAssemblyAsmPrinter::EmitFunctionBodyStart() {
148  if (!MFI->getParams().empty()) {
149    MCInst Param;
150    Param.setOpcode(WebAssembly::PARAM);
151    for (MVT VT : MFI->getParams())
152      Param.addOperand(MCOperand::createImm(VT.SimpleTy));
153    EmitToStreamer(*OutStreamer, Param);
154  }
155
156  SmallVector<MVT, 4> ResultVTs;
157  const Function &F(*MF->getFunction());
158  ComputeLegalValueVTs(F, TM, F.getReturnType(), ResultVTs);
159  // If the return type needs to be legalized it will get converted into
160  // passing a pointer.
161  if (ResultVTs.size() == 1) {
162    MCInst Result;
163    Result.setOpcode(WebAssembly::RESULT);
164    Result.addOperand(MCOperand::createImm(ResultVTs.front().SimpleTy));
165    EmitToStreamer(*OutStreamer, Result);
166  }
167
168  bool AnyWARegs = false;
169  MCInst Local;
170  Local.setOpcode(WebAssembly::LOCAL);
171  for (unsigned Idx = 0, IdxE = MRI->getNumVirtRegs(); Idx != IdxE; ++Idx) {
172    unsigned VReg = TargetRegisterInfo::index2VirtReg(Idx);
173    unsigned WAReg = MFI->getWAReg(VReg);
174    // Don't declare unused registers.
175    if (WAReg == WebAssemblyFunctionInfo::UnusedReg)
176      continue;
177    // Don't redeclare parameters.
178    if (WAReg < MFI->getParams().size())
179      continue;
180    // Don't declare stackified registers.
181    if (int(WAReg) < 0)
182      continue;
183    Local.addOperand(MCOperand::createImm(getRegType(VReg).SimpleTy));
184    AnyWARegs = true;
185  }
186  auto &PhysRegs = MFI->getPhysRegs();
187  for (unsigned PReg = 0; PReg < PhysRegs.size(); ++PReg) {
188    if (PhysRegs[PReg] == -1U)
189      continue;
190    Local.addOperand(MCOperand::createImm(getRegType(PReg).SimpleTy));
191    AnyWARegs = true;
192  }
193  if (AnyWARegs)
194    EmitToStreamer(*OutStreamer, Local);
195
196  AsmPrinter::EmitFunctionBodyStart();
197}
198
199void WebAssemblyAsmPrinter::EmitInstruction(const MachineInstr *MI) {
200  DEBUG(dbgs() << "EmitInstruction: " << *MI << '\n');
201
202  switch (MI->getOpcode()) {
203  case WebAssembly::ARGUMENT_I32:
204  case WebAssembly::ARGUMENT_I64:
205  case WebAssembly::ARGUMENT_F32:
206  case WebAssembly::ARGUMENT_F64:
207    // These represent values which are live into the function entry, so there's
208    // no instruction to emit.
209    break;
210  case WebAssembly::LOOP_END:
211    // This is a no-op which just exists to tell AsmPrinter.cpp that there's a
212    // fallthrough which nevertheless requires a label for the destination here.
213    break;
214  default: {
215    WebAssemblyMCInstLower MCInstLowering(OutContext, *this);
216    MCInst TmpInst;
217    MCInstLowering.Lower(MI, TmpInst);
218    EmitToStreamer(*OutStreamer, TmpInst);
219    break;
220  }
221  }
222}
223
224bool WebAssemblyAsmPrinter::PrintAsmOperand(const MachineInstr *MI,
225                                            unsigned OpNo, unsigned AsmVariant,
226                                            const char *ExtraCode,
227                                            raw_ostream &OS) {
228  if (AsmVariant != 0)
229    report_fatal_error("There are no defined alternate asm variants");
230
231  // First try the generic code, which knows about modifiers like 'c' and 'n'.
232  if (!AsmPrinter::PrintAsmOperand(MI, OpNo, AsmVariant, ExtraCode, OS))
233    return false;
234
235  if (!ExtraCode) {
236    const MachineOperand &MO = MI->getOperand(OpNo);
237    switch (MO.getType()) {
238    case MachineOperand::MO_Immediate:
239      OS << MO.getImm();
240      return false;
241    case MachineOperand::MO_Register:
242      OS << regToString(MO);
243      return false;
244    case MachineOperand::MO_GlobalAddress:
245      getSymbol(MO.getGlobal())->print(OS, MAI);
246      printOffset(MO.getOffset(), OS);
247      return false;
248    case MachineOperand::MO_ExternalSymbol:
249      GetExternalSymbolSymbol(MO.getSymbolName())->print(OS, MAI);
250      printOffset(MO.getOffset(), OS);
251      return false;
252    case MachineOperand::MO_MachineBasicBlock:
253      MO.getMBB()->getSymbol()->print(OS, MAI);
254      return false;
255    default:
256      break;
257    }
258  }
259
260  return true;
261}
262
263bool WebAssemblyAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
264                                                  unsigned OpNo,
265                                                  unsigned AsmVariant,
266                                                  const char *ExtraCode,
267                                                  raw_ostream &OS) {
268  if (AsmVariant != 0)
269    report_fatal_error("There are no defined alternate asm variants");
270
271  if (!ExtraCode) {
272    // TODO: For now, we just hard-code 0 as the constant offset; teach
273    // SelectInlineAsmMemoryOperand how to do address mode matching.
274    OS << "0(" + regToString(MI->getOperand(OpNo)) + ')';
275    return false;
276  }
277
278  return AsmPrinter::PrintAsmMemoryOperand(MI, OpNo, AsmVariant, ExtraCode, OS);
279}
280
281// Force static initialization.
282extern "C" void LLVMInitializeWebAssemblyAsmPrinter() {
283  RegisterAsmPrinter<WebAssemblyAsmPrinter> X(TheWebAssemblyTarget32);
284  RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(TheWebAssemblyTarget64);
285}
286