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"
37 using namespace llvm;
38 
39 #define DEBUG_TYPE "asm-printer"
40 
41 namespace {
42 
43 class WebAssemblyAsmPrinter final : public AsmPrinter {
44   const MachineRegisterInfo *MRI;
45   const WebAssemblyFunctionInfo *MFI;
46 
47 public:
48   WebAssemblyAsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer)
49       : AsmPrinter(TM, std::move(Streamer)), MRI(nullptr), MFI(nullptr) {}
50 
51 private:
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 
95 MVT 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 
108 const char *WebAssemblyAsmPrinter::toString(MVT VT) const {
109   return WebAssembly::TypeToString(VT);
110 }
111 
112 std::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 
122 WebAssemblyTargetStreamer *
123 WebAssemblyAsmPrinter::getTargetStreamer() {
124   MCTargetStreamer *TS = OutStreamer->getTargetStreamer();
125   return static_cast<WebAssemblyTargetStreamer *>(TS);
126 }
127 
128 //===----------------------------------------------------------------------===//
129 // WebAssemblyAsmPrinter Implementation.
130 //===----------------------------------------------------------------------===//
131 
132 void WebAssemblyAsmPrinter::EmitConstantPool() {
133   assert(MF->getConstantPool()->getConstants().empty() &&
134          "WebAssembly disables constant pools");
135 }
136 
137 void WebAssemblyAsmPrinter::EmitJumpTableInfo() {
138   // Nothing to do; jump tables are incorporated into the instruction stream.
139 }
140 
141 static 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 
157 void 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 
200 void WebAssemblyAsmPrinter::EmitFunctionBodyEnd() {
201   getTargetStreamer()->emitEndFunc();
202 }
203 
204 void 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 
225 const 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 
233 bool 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 
272 bool 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.
291 extern "C" void LLVMInitializeWebAssemblyAsmPrinter() {
292   RegisterAsmPrinter<WebAssemblyAsmPrinter> X(TheWebAssemblyTarget32);
293   RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(TheWebAssemblyTarget64);
294 }
295