WebAssemblyAsmPrinter.cpp revision 294024 
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 "MCTargetDesc/WebAssemblyTargetStreamer.h"
21#include "WebAssemblyMCInstLower.h"
22#include "WebAssemblyMachineFunctionInfo.h"
23#include "WebAssemblyRegisterInfo.h"
24#include "WebAssemblySubtarget.h"
25#include "llvm/ADT/StringExtras.h"
26#include "llvm/CodeGen/Analysis.h"
27#include "llvm/CodeGen/AsmPrinter.h"
28#include "llvm/CodeGen/MachineConstantPool.h"
29#include "llvm/CodeGen/MachineInstr.h"
30#include "llvm/IR/DataLayout.h"
31#include "llvm/MC/MCContext.h"
32#include "llvm/MC/MCStreamer.h"
33#include "llvm/MC/MCSymbol.h"
34#include "llvm/Support/Debug.h"
35#include "llvm/Support/TargetRegistry.h"
36#include "llvm/Support/raw_ostream.h"
37using namespace llvm;
38
39#define DEBUG_TYPE "asm-printer"
40
41namespace {
42
43class WebAssemblyAsmPrinter final : public AsmPrinter {
44  const MachineRegisterInfo *MRI;
45  const WebAssemblyFunctionInfo *MFI;
46
47public:
48  WebAssemblyAsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer)
49      : AsmPrinter(TM, std::move(Streamer)), MRI(nullptr), MFI(nullptr) {}
50
51private:
52  const char *getPassName() const override {
53    return "WebAssembly Assembly Printer";
54  }
55
56  //===------------------------------------------------------------------===//
57  // MachineFunctionPass Implementation.
58  //===------------------------------------------------------------------===//
59
60  bool runOnMachineFunction(MachineFunction &MF) override {
61    MRI = &MF.getRegInfo();
62    MFI = MF.getInfo<WebAssemblyFunctionInfo>();
63    return AsmPrinter::runOnMachineFunction(MF);
64  }
65
66  //===------------------------------------------------------------------===//
67  // AsmPrinter Implementation.
68  //===------------------------------------------------------------------===//
69
70  void EmitJumpTableInfo() override;
71  void EmitConstantPool() override;
72  void EmitFunctionBodyStart() override;
73  void EmitFunctionBodyEnd() override;
74  void EmitInstruction(const MachineInstr *MI) override;
75  const MCExpr *lowerConstant(const Constant *CV) override;
76  bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
77                       unsigned AsmVariant, const char *ExtraCode,
78                       raw_ostream &OS) override;
79  bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
80                             unsigned AsmVariant, const char *ExtraCode,
81                             raw_ostream &OS) override;
82
83  MVT getRegType(unsigned RegNo) const;
84  const char *toString(MVT VT) const;
85  std::string regToString(const MachineOperand &MO);
86  WebAssemblyTargetStreamer *getTargetStreamer();
87};
88
89} // end anonymous namespace
90
91//===----------------------------------------------------------------------===//
92// Helpers.
93//===----------------------------------------------------------------------===//
94
95MVT WebAssemblyAsmPrinter::getRegType(unsigned RegNo) const {
96  const TargetRegisterClass *TRC =
97      TargetRegisterInfo::isVirtualRegister(RegNo)
98          ? MRI->getRegClass(RegNo)
99          : MRI->getTargetRegisterInfo()->getMinimalPhysRegClass(RegNo);
100  for (MVT T : {MVT::i32, MVT::i64, MVT::f32, MVT::f64})
101    if (TRC->hasType(T))
102      return T;
103  DEBUG(errs() << "Unknown type for register number: " << RegNo);
104  llvm_unreachable("Unknown register type");
105  return MVT::Other;
106}
107
108const char *WebAssemblyAsmPrinter::toString(MVT VT) const {
109  return WebAssembly::TypeToString(VT);
110}
111
112std::string WebAssemblyAsmPrinter::regToString(const MachineOperand &MO) {
113  unsigned RegNo = MO.getReg();
114  assert(TargetRegisterInfo::isVirtualRegister(RegNo) &&
115         "Unlowered physical register encountered during assembly printing");
116  assert(!MFI->isVRegStackified(RegNo));
117  unsigned WAReg = MFI->getWAReg(RegNo);
118  assert(WAReg != WebAssemblyFunctionInfo::UnusedReg);
119  return '$' + utostr(WAReg);
120}
121
122WebAssemblyTargetStreamer *
123WebAssemblyAsmPrinter::getTargetStreamer() {
124  MCTargetStreamer *TS = OutStreamer->getTargetStreamer();
125  return static_cast<WebAssemblyTargetStreamer *>(TS);
126}
127
128//===----------------------------------------------------------------------===//
129// WebAssemblyAsmPrinter Implementation.
130//===----------------------------------------------------------------------===//
131
132void WebAssemblyAsmPrinter::EmitConstantPool() {
133  assert(MF->getConstantPool()->getConstants().empty() &&
134         "WebAssembly disables constant pools");
135}
136
137void WebAssemblyAsmPrinter::EmitJumpTableInfo() {
138  // Nothing to do; jump tables are incorporated into the instruction stream.
139}
140
141static void ComputeLegalValueVTs(const Function &F, const TargetMachine &TM,
142                                 Type *Ty, SmallVectorImpl<MVT> &ValueVTs) {
143  const DataLayout &DL(F.getParent()->getDataLayout());
144  const WebAssemblyTargetLowering &TLI =
145      *TM.getSubtarget<WebAssemblySubtarget>(F).getTargetLowering();
146  SmallVector<EVT, 4> VTs;
147  ComputeValueVTs(TLI, DL, Ty, VTs);
148
149  for (EVT VT : VTs) {
150    unsigned NumRegs = TLI.getNumRegisters(F.getContext(), VT);
151    MVT RegisterVT = TLI.getRegisterType(F.getContext(), VT);
152    for (unsigned i = 0; i != NumRegs; ++i)
153      ValueVTs.push_back(RegisterVT);
154  }
155}
156
157void WebAssemblyAsmPrinter::EmitFunctionBodyStart() {
158  if (!MFI->getParams().empty())
159    getTargetStreamer()->emitParam(MFI->getParams());
160
161  SmallVector<MVT, 4> ResultVTs;
162  const Function &F(*MF->getFunction());
163  ComputeLegalValueVTs(F, TM, F.getReturnType(), ResultVTs);
164
165  // If the return type needs to be legalized it will get converted into
166  // passing a pointer.
167  if (ResultVTs.size() == 1)
168    getTargetStreamer()->emitResult(ResultVTs);
169
170  bool AnyWARegs = false;
171  SmallVector<MVT, 16> LocalTypes;
172  for (unsigned Idx = 0, IdxE = MRI->getNumVirtRegs(); Idx != IdxE; ++Idx) {
173    unsigned VReg = TargetRegisterInfo::index2VirtReg(Idx);
174    unsigned WAReg = MFI->getWAReg(VReg);
175    // Don't declare unused registers.
176    if (WAReg == WebAssemblyFunctionInfo::UnusedReg)
177      continue;
178    // Don't redeclare parameters.
179    if (WAReg < MFI->getParams().size())
180      continue;
181    // Don't declare stackified registers.
182    if (int(WAReg) < 0)
183      continue;
184    LocalTypes.push_back(getRegType(VReg));
185    AnyWARegs = true;
186  }
187  auto &PhysRegs = MFI->getPhysRegs();
188  for (unsigned PReg = 0; PReg < PhysRegs.size(); ++PReg) {
189    if (PhysRegs[PReg] == -1U)
190      continue;
191    LocalTypes.push_back(getRegType(PReg));
192    AnyWARegs = true;
193  }
194  if (AnyWARegs)
195    getTargetStreamer()->emitLocal(LocalTypes);
196
197  AsmPrinter::EmitFunctionBodyStart();
198}
199
200void WebAssemblyAsmPrinter::EmitFunctionBodyEnd() {
201  getTargetStreamer()->emitEndFunc();
202}
203
204void WebAssemblyAsmPrinter::EmitInstruction(const MachineInstr *MI) {
205  DEBUG(dbgs() << "EmitInstruction: " << *MI << '\n');
206
207  switch (MI->getOpcode()) {
208  case WebAssembly::ARGUMENT_I32:
209  case WebAssembly::ARGUMENT_I64:
210  case WebAssembly::ARGUMENT_F32:
211  case WebAssembly::ARGUMENT_F64:
212    // These represent values which are live into the function entry, so there's
213    // no instruction to emit.
214    break;
215  default: {
216    WebAssemblyMCInstLower MCInstLowering(OutContext, *this);
217    MCInst TmpInst;
218    MCInstLowering.Lower(MI, TmpInst);
219    EmitToStreamer(*OutStreamer, TmpInst);
220    break;
221  }
222  }
223}
224
225const MCExpr *WebAssemblyAsmPrinter::lowerConstant(const Constant *CV) {
226  if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV))
227    if (GV->getValueType()->isFunctionTy())
228      return MCSymbolRefExpr::create(
229          getSymbol(GV), MCSymbolRefExpr::VK_WebAssembly_FUNCTION, OutContext);
230  return AsmPrinter::lowerConstant(CV);
231}
232
233bool WebAssemblyAsmPrinter::PrintAsmOperand(const MachineInstr *MI,
234                                            unsigned OpNo, unsigned AsmVariant,
235                                            const char *ExtraCode,
236                                            raw_ostream &OS) {
237  if (AsmVariant != 0)
238    report_fatal_error("There are no defined alternate asm variants");
239
240  // First try the generic code, which knows about modifiers like 'c' and 'n'.
241  if (!AsmPrinter::PrintAsmOperand(MI, OpNo, AsmVariant, ExtraCode, OS))
242    return false;
243
244  if (!ExtraCode) {
245    const MachineOperand &MO = MI->getOperand(OpNo);
246    switch (MO.getType()) {
247    case MachineOperand::MO_Immediate:
248      OS << MO.getImm();
249      return false;
250    case MachineOperand::MO_Register:
251      OS << regToString(MO);
252      return false;
253    case MachineOperand::MO_GlobalAddress:
254      getSymbol(MO.getGlobal())->print(OS, MAI);
255      printOffset(MO.getOffset(), OS);
256      return false;
257    case MachineOperand::MO_ExternalSymbol:
258      GetExternalSymbolSymbol(MO.getSymbolName())->print(OS, MAI);
259      printOffset(MO.getOffset(), OS);
260      return false;
261    case MachineOperand::MO_MachineBasicBlock:
262      MO.getMBB()->getSymbol()->print(OS, MAI);
263      return false;
264    default:
265      break;
266    }
267  }
268
269  return true;
270}
271
272bool WebAssemblyAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
273                                                  unsigned OpNo,
274                                                  unsigned AsmVariant,
275                                                  const char *ExtraCode,
276                                                  raw_ostream &OS) {
277  if (AsmVariant != 0)
278    report_fatal_error("There are no defined alternate asm variants");
279
280  if (!ExtraCode) {
281    // TODO: For now, we just hard-code 0 as the constant offset; teach
282    // SelectInlineAsmMemoryOperand how to do address mode matching.
283    OS << "0(" + regToString(MI->getOperand(OpNo)) + ')';
284    return false;
285  }
286
287  return AsmPrinter::PrintAsmMemoryOperand(MI, OpNo, AsmVariant, ExtraCode, OS);
288}
289
290// Force static initialization.
291extern "C" void LLVMInitializeWebAssemblyAsmPrinter() {
292  RegisterAsmPrinter<WebAssemblyAsmPrinter> X(TheWebAssemblyTarget32);
293  RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(TheWebAssemblyTarget64);
294}
295