WebAssemblyAsmPrinter.cpp revision 314564 
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 "InstPrinter/WebAssemblyInstPrinter.h"
18#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
19#include "MCTargetDesc/WebAssemblyTargetStreamer.h"
20#include "WebAssembly.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  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  StringRef 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 EmitEndOfAsmFile(Module &M) override;
71  void EmitJumpTableInfo() override;
72  void EmitConstantPool() override;
73  void EmitFunctionBodyStart() override;
74  void EmitFunctionBodyEnd() override;
75  void EmitInstruction(const MachineInstr *MI) override;
76  const MCExpr *lowerConstant(const Constant *CV) override;
77  bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
78                       unsigned AsmVariant, const char *ExtraCode,
79                       raw_ostream &OS) override;
80  bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
81                             unsigned AsmVariant, const char *ExtraCode,
82                             raw_ostream &OS) override;
83
84  MVT getRegType(unsigned RegNo) 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 = MRI->getRegClass(RegNo);
97  for (MVT T : {MVT::i32, MVT::i64, MVT::f32, MVT::f64, MVT::v16i8, MVT::v8i16,
98                MVT::v4i32, MVT::v4f32})
99    if (TRC->hasType(T))
100      return T;
101  DEBUG(errs() << "Unknown type for register number: " << RegNo);
102  llvm_unreachable("Unknown register type");
103  return MVT::Other;
104}
105
106std::string WebAssemblyAsmPrinter::regToString(const MachineOperand &MO) {
107  unsigned RegNo = MO.getReg();
108  assert(TargetRegisterInfo::isVirtualRegister(RegNo) &&
109         "Unlowered physical register encountered during assembly printing");
110  assert(!MFI->isVRegStackified(RegNo));
111  unsigned WAReg = MFI->getWAReg(RegNo);
112  assert(WAReg != WebAssemblyFunctionInfo::UnusedReg);
113  return '$' + utostr(WAReg);
114}
115
116WebAssemblyTargetStreamer *WebAssemblyAsmPrinter::getTargetStreamer() {
117  MCTargetStreamer *TS = OutStreamer->getTargetStreamer();
118  return static_cast<WebAssemblyTargetStreamer *>(TS);
119}
120
121//===----------------------------------------------------------------------===//
122// WebAssemblyAsmPrinter Implementation.
123//===----------------------------------------------------------------------===//
124
125void WebAssemblyAsmPrinter::EmitEndOfAsmFile(Module &M) {
126  for (const auto &F : M) {
127    // Emit function type info for all undefined functions
128    if (F.isDeclarationForLinker() && !F.isIntrinsic()) {
129      SmallVector<MVT, 4> Results;
130      SmallVector<MVT, 4> Params;
131      ComputeSignatureVTs(F, TM, Params, Results);
132      getTargetStreamer()->emitIndirectFunctionType(F.getName(), Params,
133                                                    Results);
134    }
135  }
136  for (const auto &G : M.globals()) {
137    if (!G.hasInitializer() && G.hasExternalLinkage()) {
138      getTargetStreamer()->emitGlobalImport(G.getGlobalIdentifier());
139    }
140  }
141}
142
143void WebAssemblyAsmPrinter::EmitConstantPool() {
144  assert(MF->getConstantPool()->getConstants().empty() &&
145         "WebAssembly disables constant pools");
146}
147
148void WebAssemblyAsmPrinter::EmitJumpTableInfo() {
149  // Nothing to do; jump tables are incorporated into the instruction stream.
150}
151
152void WebAssemblyAsmPrinter::EmitFunctionBodyStart() {
153  if (!MFI->getParams().empty())
154    getTargetStreamer()->emitParam(MFI->getParams());
155
156  SmallVector<MVT, 4> ResultVTs;
157  const Function &F(*MF->getFunction());
158
159  // Emit the function index.
160  if (MDNode *Idx = F.getMetadata("wasm.index")) {
161    assert(Idx->getNumOperands() == 1);
162
163    getTargetStreamer()->emitIndIdx(AsmPrinter::lowerConstant(
164        cast<ConstantAsMetadata>(Idx->getOperand(0))->getValue()));
165  }
166
167  ComputeLegalValueVTs(F, TM, F.getReturnType(), ResultVTs);
168
169  // If the return type needs to be legalized it will get converted into
170  // passing a pointer.
171  if (ResultVTs.size() == 1)
172    getTargetStreamer()->emitResult(ResultVTs);
173
174  // FIXME: When ExplicitLocals is enabled by default, we won't need
175  // to define the locals here (and MFI can go back to being pointer-to-const).
176  for (unsigned Idx = 0, IdxE = MRI->getNumVirtRegs(); Idx != IdxE; ++Idx) {
177    unsigned VReg = TargetRegisterInfo::index2VirtReg(Idx);
178    unsigned WAReg = MFI->getWAReg(VReg);
179    // Don't declare unused registers.
180    if (WAReg == WebAssemblyFunctionInfo::UnusedReg)
181      continue;
182    // Don't redeclare parameters.
183    if (WAReg < MFI->getParams().size())
184      continue;
185    // Don't declare stackified registers.
186    if (int(WAReg) < 0)
187      continue;
188    MFI->addLocal(getRegType(VReg));
189  }
190
191  getTargetStreamer()->emitLocal(MFI->getLocals());
192
193  AsmPrinter::EmitFunctionBodyStart();
194}
195
196void WebAssemblyAsmPrinter::EmitFunctionBodyEnd() {
197  getTargetStreamer()->emitEndFunc();
198}
199
200void WebAssemblyAsmPrinter::EmitInstruction(const MachineInstr *MI) {
201  DEBUG(dbgs() << "EmitInstruction: " << *MI << '\n');
202
203  switch (MI->getOpcode()) {
204  case WebAssembly::ARGUMENT_I32:
205  case WebAssembly::ARGUMENT_I64:
206  case WebAssembly::ARGUMENT_F32:
207  case WebAssembly::ARGUMENT_F64:
208  case WebAssembly::ARGUMENT_v16i8:
209  case WebAssembly::ARGUMENT_v8i16:
210  case WebAssembly::ARGUMENT_v4i32:
211  case WebAssembly::ARGUMENT_v4f32:
212    // These represent values which are live into the function entry, so there's
213    // no instruction to emit.
214    break;
215  case WebAssembly::FALLTHROUGH_RETURN_I32:
216  case WebAssembly::FALLTHROUGH_RETURN_I64:
217  case WebAssembly::FALLTHROUGH_RETURN_F32:
218  case WebAssembly::FALLTHROUGH_RETURN_F64:
219  case WebAssembly::FALLTHROUGH_RETURN_v16i8:
220  case WebAssembly::FALLTHROUGH_RETURN_v8i16:
221  case WebAssembly::FALLTHROUGH_RETURN_v4i32:
222  case WebAssembly::FALLTHROUGH_RETURN_v4f32: {
223    // These instructions represent the implicit return at the end of a
224    // function body. The operand is always a pop.
225    assert(MFI->isVRegStackified(MI->getOperand(0).getReg()));
226
227    if (isVerbose()) {
228      OutStreamer->AddComment("fallthrough-return: $pop" +
229                              utostr(MFI->getWARegStackId(
230                                  MFI->getWAReg(MI->getOperand(0).getReg()))));
231      OutStreamer->AddBlankLine();
232    }
233    break;
234  }
235  case WebAssembly::FALLTHROUGH_RETURN_VOID:
236    // This instruction represents the implicit return at the end of a
237    // function body with no return value.
238    if (isVerbose()) {
239      OutStreamer->AddComment("fallthrough-return");
240      OutStreamer->AddBlankLine();
241    }
242    break;
243  default: {
244    WebAssemblyMCInstLower MCInstLowering(OutContext, *this);
245    MCInst TmpInst;
246    MCInstLowering.Lower(MI, TmpInst);
247    EmitToStreamer(*OutStreamer, TmpInst);
248    break;
249  }
250  }
251}
252
253const MCExpr *WebAssemblyAsmPrinter::lowerConstant(const Constant *CV) {
254  if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV))
255    if (GV->getValueType()->isFunctionTy())
256      return MCSymbolRefExpr::create(
257          getSymbol(GV), MCSymbolRefExpr::VK_WebAssembly_FUNCTION, OutContext);
258  return AsmPrinter::lowerConstant(CV);
259}
260
261bool WebAssemblyAsmPrinter::PrintAsmOperand(const MachineInstr *MI,
262                                            unsigned OpNo, unsigned AsmVariant,
263                                            const char *ExtraCode,
264                                            raw_ostream &OS) {
265  if (AsmVariant != 0)
266    report_fatal_error("There are no defined alternate asm variants");
267
268  // First try the generic code, which knows about modifiers like 'c' and 'n'.
269  if (!AsmPrinter::PrintAsmOperand(MI, OpNo, AsmVariant, ExtraCode, OS))
270    return false;
271
272  if (!ExtraCode) {
273    const MachineOperand &MO = MI->getOperand(OpNo);
274    switch (MO.getType()) {
275    case MachineOperand::MO_Immediate:
276      OS << MO.getImm();
277      return false;
278    case MachineOperand::MO_Register:
279      OS << regToString(MO);
280      return false;
281    case MachineOperand::MO_GlobalAddress:
282      getSymbol(MO.getGlobal())->print(OS, MAI);
283      printOffset(MO.getOffset(), OS);
284      return false;
285    case MachineOperand::MO_ExternalSymbol:
286      GetExternalSymbolSymbol(MO.getSymbolName())->print(OS, MAI);
287      printOffset(MO.getOffset(), OS);
288      return false;
289    case MachineOperand::MO_MachineBasicBlock:
290      MO.getMBB()->getSymbol()->print(OS, MAI);
291      return false;
292    default:
293      break;
294    }
295  }
296
297  return true;
298}
299
300bool WebAssemblyAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
301                                                  unsigned OpNo,
302                                                  unsigned AsmVariant,
303                                                  const char *ExtraCode,
304                                                  raw_ostream &OS) {
305  if (AsmVariant != 0)
306    report_fatal_error("There are no defined alternate asm variants");
307
308  if (!ExtraCode) {
309    // TODO: For now, we just hard-code 0 as the constant offset; teach
310    // SelectInlineAsmMemoryOperand how to do address mode matching.
311    OS << "0(" + regToString(MI->getOperand(OpNo)) + ')';
312    return false;
313  }
314
315  return AsmPrinter::PrintAsmMemoryOperand(MI, OpNo, AsmVariant, ExtraCode, OS);
316}
317
318// Force static initialization.
319extern "C" void LLVMInitializeWebAssemblyAsmPrinter() {
320  RegisterAsmPrinter<WebAssemblyAsmPrinter> X(getTheWebAssemblyTarget32());
321  RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(getTheWebAssemblyTarget64());
322}
323