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:
WebAssemblyAsmPrinter(TargetMachine & TM,std::unique_ptr<MCStreamer> Streamer)48 WebAssemblyAsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer)
49 : AsmPrinter(TM, std::move(Streamer)), MRI(nullptr), MFI(nullptr) {}
50
51 private:
getPassName() const52 const char *getPassName() const override {
53 return "WebAssembly Assembly Printer";
54 }
55
56 //===------------------------------------------------------------------===//
57 // MachineFunctionPass Implementation.
58 //===------------------------------------------------------------------===//
59
runOnMachineFunction(MachineFunction & MF)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 const char *toString(MVT VT) const;
86 std::string regToString(const MachineOperand &MO);
87 WebAssemblyTargetStreamer *getTargetStreamer();
88 };
89
90 } // end anonymous namespace
91
92 //===----------------------------------------------------------------------===//
93 // Helpers.
94 //===----------------------------------------------------------------------===//
95
getRegType(unsigned RegNo) const96 MVT WebAssemblyAsmPrinter::getRegType(unsigned RegNo) const {
97 const TargetRegisterClass *TRC = MRI->getRegClass(RegNo);
98 for (MVT T : {MVT::i32, MVT::i64, MVT::f32, MVT::f64})
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
toString(MVT VT) const106 const char *WebAssemblyAsmPrinter::toString(MVT VT) const {
107 return WebAssembly::TypeToString(VT);
108 }
109
regToString(const MachineOperand & MO)110 std::string WebAssemblyAsmPrinter::regToString(const MachineOperand &MO) {
111 unsigned RegNo = MO.getReg();
112 assert(TargetRegisterInfo::isVirtualRegister(RegNo) &&
113 "Unlowered physical register encountered during assembly printing");
114 assert(!MFI->isVRegStackified(RegNo));
115 unsigned WAReg = MFI->getWAReg(RegNo);
116 assert(WAReg != WebAssemblyFunctionInfo::UnusedReg);
117 return '$' + utostr(WAReg);
118 }
119
getTargetStreamer()120 WebAssemblyTargetStreamer *WebAssemblyAsmPrinter::getTargetStreamer() {
121 MCTargetStreamer *TS = OutStreamer->getTargetStreamer();
122 return static_cast<WebAssemblyTargetStreamer *>(TS);
123 }
124
125 //===----------------------------------------------------------------------===//
126 // WebAssemblyAsmPrinter Implementation.
127 //===----------------------------------------------------------------------===//
ComputeLegalValueVTs(const Function & F,const TargetMachine & TM,Type * Ty,SmallVectorImpl<MVT> & ValueVTs)128 static void ComputeLegalValueVTs(const Function &F, const TargetMachine &TM,
129 Type *Ty, SmallVectorImpl<MVT> &ValueVTs) {
130 const DataLayout &DL(F.getParent()->getDataLayout());
131 const WebAssemblyTargetLowering &TLI =
132 *TM.getSubtarget<WebAssemblySubtarget>(F).getTargetLowering();
133 SmallVector<EVT, 4> VTs;
134 ComputeValueVTs(TLI, DL, Ty, VTs);
135
136 for (EVT VT : VTs) {
137 unsigned NumRegs = TLI.getNumRegisters(F.getContext(), VT);
138 MVT RegisterVT = TLI.getRegisterType(F.getContext(), VT);
139 for (unsigned i = 0; i != NumRegs; ++i)
140 ValueVTs.push_back(RegisterVT);
141 }
142 }
143
EmitEndOfAsmFile(Module & M)144 void WebAssemblyAsmPrinter::EmitEndOfAsmFile(Module &M) {
145 for (const auto &F : M) {
146 // Emit function type info for all undefined functions
147 if (F.isDeclarationForLinker() && !F.isIntrinsic()) {
148 SmallVector<MVT, 4> SignatureVTs;
149 ComputeLegalValueVTs(F, TM, F.getReturnType(), SignatureVTs);
150 size_t NumResults = SignatureVTs.size();
151 if (SignatureVTs.size() > 1) {
152 // WebAssembly currently can't lower returns of multiple values without
153 // demoting to sret (see WebAssemblyTargetLowering::CanLowerReturn). So
154 // replace multiple return values with a pointer parameter.
155 SignatureVTs.clear();
156 SignatureVTs.push_back(
157 MVT::getIntegerVT(M.getDataLayout().getPointerSizeInBits()));
158 NumResults = 0;
159 }
160
161 for (auto &Arg : F.args()) {
162 ComputeLegalValueVTs(F, TM, Arg.getType(), SignatureVTs);
163 }
164
165 getTargetStreamer()->emitIndirectFunctionType(F.getName(), SignatureVTs,
166 NumResults);
167 }
168 }
169 }
170
EmitConstantPool()171 void WebAssemblyAsmPrinter::EmitConstantPool() {
172 assert(MF->getConstantPool()->getConstants().empty() &&
173 "WebAssembly disables constant pools");
174 }
175
EmitJumpTableInfo()176 void WebAssemblyAsmPrinter::EmitJumpTableInfo() {
177 // Nothing to do; jump tables are incorporated into the instruction stream.
178 }
179
EmitFunctionBodyStart()180 void WebAssemblyAsmPrinter::EmitFunctionBodyStart() {
181 if (!MFI->getParams().empty())
182 getTargetStreamer()->emitParam(MFI->getParams());
183
184 SmallVector<MVT, 4> ResultVTs;
185 const Function &F(*MF->getFunction());
186 ComputeLegalValueVTs(F, TM, F.getReturnType(), ResultVTs);
187
188 // If the return type needs to be legalized it will get converted into
189 // passing a pointer.
190 if (ResultVTs.size() == 1)
191 getTargetStreamer()->emitResult(ResultVTs);
192
193 bool AnyWARegs = false;
194 SmallVector<MVT, 16> LocalTypes;
195 for (unsigned Idx = 0, IdxE = MRI->getNumVirtRegs(); Idx != IdxE; ++Idx) {
196 unsigned VReg = TargetRegisterInfo::index2VirtReg(Idx);
197 unsigned WAReg = MFI->getWAReg(VReg);
198 // Don't declare unused registers.
199 if (WAReg == WebAssemblyFunctionInfo::UnusedReg)
200 continue;
201 // Don't redeclare parameters.
202 if (WAReg < MFI->getParams().size())
203 continue;
204 // Don't declare stackified registers.
205 if (int(WAReg) < 0)
206 continue;
207 LocalTypes.push_back(getRegType(VReg));
208 AnyWARegs = true;
209 }
210 if (AnyWARegs)
211 getTargetStreamer()->emitLocal(LocalTypes);
212
213 AsmPrinter::EmitFunctionBodyStart();
214 }
215
EmitFunctionBodyEnd()216 void WebAssemblyAsmPrinter::EmitFunctionBodyEnd() {
217 getTargetStreamer()->emitEndFunc();
218 }
219
EmitInstruction(const MachineInstr * MI)220 void WebAssemblyAsmPrinter::EmitInstruction(const MachineInstr *MI) {
221 DEBUG(dbgs() << "EmitInstruction: " << *MI << '\n');
222
223 switch (MI->getOpcode()) {
224 case WebAssembly::ARGUMENT_I32:
225 case WebAssembly::ARGUMENT_I64:
226 case WebAssembly::ARGUMENT_F32:
227 case WebAssembly::ARGUMENT_F64:
228 // These represent values which are live into the function entry, so there's
229 // no instruction to emit.
230 break;
231 case WebAssembly::FALLTHROUGH_RETURN_I32:
232 case WebAssembly::FALLTHROUGH_RETURN_I64:
233 case WebAssembly::FALLTHROUGH_RETURN_F32:
234 case WebAssembly::FALLTHROUGH_RETURN_F64: {
235 // These instructions represent the implicit return at the end of a
236 // function body. The operand is always a pop.
237 assert(MFI->isVRegStackified(MI->getOperand(0).getReg()));
238
239 if (isVerbose()) {
240 OutStreamer->AddComment("fallthrough-return: $pop" +
241 utostr(MFI->getWARegStackId(
242 MFI->getWAReg(MI->getOperand(0).getReg()))));
243 OutStreamer->AddBlankLine();
244 }
245 break;
246 }
247 case WebAssembly::FALLTHROUGH_RETURN_VOID:
248 // This instruction represents the implicit return at the end of a
249 // function body with no return value.
250 if (isVerbose()) {
251 OutStreamer->AddComment("fallthrough-return");
252 OutStreamer->AddBlankLine();
253 }
254 break;
255 default: {
256 WebAssemblyMCInstLower MCInstLowering(OutContext, *this);
257 MCInst TmpInst;
258 MCInstLowering.Lower(MI, TmpInst);
259 EmitToStreamer(*OutStreamer, TmpInst);
260 break;
261 }
262 }
263 }
264
lowerConstant(const Constant * CV)265 const MCExpr *WebAssemblyAsmPrinter::lowerConstant(const Constant *CV) {
266 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV))
267 if (GV->getValueType()->isFunctionTy())
268 return MCSymbolRefExpr::create(
269 getSymbol(GV), MCSymbolRefExpr::VK_WebAssembly_FUNCTION, OutContext);
270 return AsmPrinter::lowerConstant(CV);
271 }
272
PrintAsmOperand(const MachineInstr * MI,unsigned OpNo,unsigned AsmVariant,const char * ExtraCode,raw_ostream & OS)273 bool WebAssemblyAsmPrinter::PrintAsmOperand(const MachineInstr *MI,
274 unsigned OpNo, 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 // First try the generic code, which knows about modifiers like 'c' and 'n'.
281 if (!AsmPrinter::PrintAsmOperand(MI, OpNo, AsmVariant, ExtraCode, OS))
282 return false;
283
284 if (!ExtraCode) {
285 const MachineOperand &MO = MI->getOperand(OpNo);
286 switch (MO.getType()) {
287 case MachineOperand::MO_Immediate:
288 OS << MO.getImm();
289 return false;
290 case MachineOperand::MO_Register:
291 OS << regToString(MO);
292 return false;
293 case MachineOperand::MO_GlobalAddress:
294 getSymbol(MO.getGlobal())->print(OS, MAI);
295 printOffset(MO.getOffset(), OS);
296 return false;
297 case MachineOperand::MO_ExternalSymbol:
298 GetExternalSymbolSymbol(MO.getSymbolName())->print(OS, MAI);
299 printOffset(MO.getOffset(), OS);
300 return false;
301 case MachineOperand::MO_MachineBasicBlock:
302 MO.getMBB()->getSymbol()->print(OS, MAI);
303 return false;
304 default:
305 break;
306 }
307 }
308
309 return true;
310 }
311
PrintAsmMemoryOperand(const MachineInstr * MI,unsigned OpNo,unsigned AsmVariant,const char * ExtraCode,raw_ostream & OS)312 bool WebAssemblyAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
313 unsigned OpNo,
314 unsigned AsmVariant,
315 const char *ExtraCode,
316 raw_ostream &OS) {
317 if (AsmVariant != 0)
318 report_fatal_error("There are no defined alternate asm variants");
319
320 if (!ExtraCode) {
321 // TODO: For now, we just hard-code 0 as the constant offset; teach
322 // SelectInlineAsmMemoryOperand how to do address mode matching.
323 OS << "0(" + regToString(MI->getOperand(OpNo)) + ')';
324 return false;
325 }
326
327 return AsmPrinter::PrintAsmMemoryOperand(MI, OpNo, AsmVariant, ExtraCode, OS);
328 }
329
330 // Force static initialization.
LLVMInitializeWebAssemblyAsmPrinter()331 extern "C" void LLVMInitializeWebAssemblyAsmPrinter() {
332 RegisterAsmPrinter<WebAssemblyAsmPrinter> X(TheWebAssemblyTarget32);
333 RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(TheWebAssemblyTarget64);
334 }
335