Line data Source code
1 : // WebAssemblyMCInstLower.cpp - Convert WebAssembly MachineInstr to an MCInst //
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 : /// This file contains code to lower WebAssembly MachineInstrs to their
12 : /// corresponding MCInst records.
13 : ///
14 : //===----------------------------------------------------------------------===//
15 :
16 : #include "WebAssemblyMCInstLower.h"
17 : #include "WebAssemblyAsmPrinter.h"
18 : #include "WebAssemblyMachineFunctionInfo.h"
19 : #include "WebAssemblyRuntimeLibcallSignatures.h"
20 : #include "WebAssemblyUtilities.h"
21 : #include "llvm/CodeGen/AsmPrinter.h"
22 : #include "llvm/CodeGen/MachineFunction.h"
23 : #include "llvm/IR/Constants.h"
24 : #include "llvm/MC/MCAsmInfo.h"
25 : #include "llvm/MC/MCContext.h"
26 : #include "llvm/MC/MCExpr.h"
27 : #include "llvm/MC/MCInst.h"
28 : #include "llvm/MC/MCSymbolWasm.h"
29 : #include "llvm/Support/ErrorHandling.h"
30 : #include "llvm/Support/raw_ostream.h"
31 : using namespace llvm;
32 :
33 : // This disables the removal of registers when lowering into MC, as required
34 : // by some current tests.
35 : static cl::opt<bool>
36 : WasmKeepRegisters("wasm-keep-registers", cl::Hidden,
37 : cl::desc("WebAssembly: output stack registers in"
38 : " instruction output for test purposes only."),
39 : cl::init(false));
40 :
41 : static unsigned regInstructionToStackInstruction(unsigned OpCode);
42 : static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI);
43 :
44 : MCSymbol *
45 810 : WebAssemblyMCInstLower::GetGlobalAddressSymbol(const MachineOperand &MO) const {
46 810 : const GlobalValue *Global = MO.getGlobal();
47 810 : MCSymbolWasm *WasmSym = cast<MCSymbolWasm>(Printer.getSymbol(Global));
48 :
49 810 : if (const auto *FuncTy = dyn_cast<FunctionType>(Global->getValueType())) {
50 461 : const MachineFunction &MF = *MO.getParent()->getParent()->getParent();
51 461 : const TargetMachine &TM = MF.getTarget();
52 461 : const Function &CurrentFunc = MF.getFunction();
53 :
54 : SmallVector<MVT, 1> ResultMVTs;
55 : SmallVector<MVT, 4> ParamMVTs;
56 461 : ComputeSignatureVTs(FuncTy, CurrentFunc, TM, ParamMVTs, ResultMVTs);
57 :
58 922 : auto Signature = SignatureFromMVTs(ResultMVTs, ParamMVTs);
59 : WasmSym->setSignature(Signature.get());
60 461 : Printer.addSignature(std::move(Signature));
61 : WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
62 : }
63 :
64 810 : return WasmSym;
65 : }
66 :
67 376 : MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol(
68 : const MachineOperand &MO) const {
69 376 : const char *Name = MO.getSymbolName();
70 : MCSymbolWasm *WasmSym =
71 752 : cast<MCSymbolWasm>(Printer.GetExternalSymbolSymbol(Name));
72 376 : const WebAssemblySubtarget &Subtarget = Printer.getSubtarget();
73 :
74 : // __stack_pointer is a global variable; all other external symbols used by
75 : // CodeGen are functions. It's OK to hardcode knowledge of specific symbols
76 : // here; this method is precisely there for fetching the signatures of known
77 : // Clang-provided symbols.
78 376 : if (strcmp(Name, "__stack_pointer") == 0) {
79 : WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);
80 254 : WasmSym->setGlobalType(wasm::WasmGlobalType{
81 : uint8_t(Subtarget.hasAddr64() ? wasm::WASM_TYPE_I64
82 : : wasm::WASM_TYPE_I32),
83 : true});
84 254 : return WasmSym;
85 : }
86 :
87 : SmallVector<wasm::ValType, 4> Returns;
88 : SmallVector<wasm::ValType, 4> Params;
89 122 : GetLibcallSignature(Subtarget, Name, Returns, Params);
90 : auto Signature =
91 244 : make_unique<wasm::WasmSignature>(std::move(Returns), std::move(Params));
92 : WasmSym->setSignature(Signature.get());
93 122 : Printer.addSignature(std::move(Signature));
94 : WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
95 :
96 : return WasmSym;
97 : }
98 :
99 1186 : MCOperand WebAssemblyMCInstLower::LowerSymbolOperand(MCSymbol *Sym,
100 : int64_t Offset,
101 : bool IsFunc,
102 : bool IsGlob) const {
103 : MCSymbolRefExpr::VariantKind VK =
104 1186 : IsFunc ? MCSymbolRefExpr::VK_WebAssembly_FUNCTION
105 603 : : IsGlob ? MCSymbolRefExpr::VK_WebAssembly_GLOBAL
106 : : MCSymbolRefExpr::VK_None;
107 :
108 1186 : const MCExpr *Expr = MCSymbolRefExpr::create(Sym, VK, Ctx);
109 :
110 1186 : if (Offset != 0) {
111 78 : if (IsFunc)
112 0 : report_fatal_error("Function addresses with offsets not supported");
113 78 : if (IsGlob)
114 0 : report_fatal_error("Global indexes with offsets not supported");
115 : Expr =
116 78 : MCBinaryExpr::createAdd(Expr, MCConstantExpr::create(Offset, Ctx), Ctx);
117 : }
118 :
119 1186 : return MCOperand::createExpr(Expr);
120 : }
121 :
122 : // Return the WebAssembly type associated with the given register class.
123 : static wasm::ValType getType(const TargetRegisterClass *RC) {
124 75 : if (RC == &WebAssembly::I32RegClass)
125 : return wasm::ValType::I32;
126 17 : if (RC == &WebAssembly::I64RegClass)
127 : return wasm::ValType::I64;
128 8 : if (RC == &WebAssembly::F32RegClass)
129 : return wasm::ValType::F32;
130 5 : if (RC == &WebAssembly::F64RegClass)
131 : return wasm::ValType::F64;
132 2 : if (RC == &WebAssembly::V128RegClass)
133 : return wasm::ValType::V128;
134 0 : llvm_unreachable("Unexpected register class");
135 : }
136 :
137 24888 : void WebAssemblyMCInstLower::Lower(const MachineInstr *MI,
138 : MCInst &OutMI) const {
139 24888 : OutMI.setOpcode(MI->getOpcode());
140 :
141 : const MCInstrDesc &Desc = MI->getDesc();
142 141996 : for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
143 117108 : const MachineOperand &MO = MI->getOperand(i);
144 :
145 : MCOperand MCOp;
146 117108 : switch (MO.getType()) {
147 0 : default:
148 0 : MI->print(errs());
149 0 : llvm_unreachable("unknown operand type");
150 0 : case MachineOperand::MO_MachineBasicBlock:
151 0 : MI->print(errs());
152 0 : llvm_unreachable("MachineBasicBlock operand should have been rewritten");
153 : case MachineOperand::MO_Register: {
154 : // Ignore all implicit register operands.
155 101169 : if (MO.isImplicit())
156 62702 : continue;
157 : const WebAssemblyFunctionInfo &MFI =
158 38467 : *MI->getParent()->getParent()->getInfo<WebAssemblyFunctionInfo>();
159 38467 : unsigned WAReg = MFI.getWAReg(MO.getReg());
160 38467 : MCOp = MCOperand::createReg(WAReg);
161 38467 : break;
162 : }
163 14546 : case MachineOperand::MO_Immediate:
164 14546 : if (i < Desc.NumOperands) {
165 14485 : const MCOperandInfo &Info = Desc.OpInfo[i];
166 14485 : if (Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) {
167 66 : MCSymbol *Sym = Printer.createTempSymbol("typeindex");
168 :
169 : SmallVector<wasm::ValType, 4> Returns;
170 : SmallVector<wasm::ValType, 4> Params;
171 :
172 : const MachineRegisterInfo &MRI =
173 33 : MI->getParent()->getParent()->getRegInfo();
174 59 : for (const MachineOperand &MO : MI->defs())
175 38 : Returns.push_back(getType(MRI.getRegClass(MO.getReg())));
176 148 : for (const MachineOperand &MO : MI->explicit_uses())
177 115 : if (MO.isReg())
178 54 : Params.push_back(getType(MRI.getRegClass(MO.getReg())));
179 :
180 : // call_indirect instructions have a callee operand at the end which
181 : // doesn't count as a param.
182 33 : if (WebAssembly::isCallIndirect(*MI))
183 : Params.pop_back();
184 :
185 : MCSymbolWasm *WasmSym = cast<MCSymbolWasm>(Sym);
186 : auto Signature = make_unique<wasm::WasmSignature>(std::move(Returns),
187 33 : std::move(Params));
188 : WasmSym->setSignature(Signature.get());
189 33 : Printer.addSignature(std::move(Signature));
190 : WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
191 :
192 33 : const MCExpr *Expr = MCSymbolRefExpr::create(
193 33 : WasmSym, MCSymbolRefExpr::VK_WebAssembly_TYPEINDEX, Ctx);
194 33 : MCOp = MCOperand::createExpr(Expr);
195 : break;
196 : }
197 : }
198 14513 : MCOp = MCOperand::createImm(MO.getImm());
199 14513 : break;
200 207 : case MachineOperand::MO_FPImmediate: {
201 : // TODO: MC converts all floating point immediate operands to double.
202 : // This is fine for numeric values, but may cause NaNs to change bits.
203 207 : const ConstantFP *Imm = MO.getFPImm();
204 414 : if (Imm->getType()->isFloatTy())
205 101 : MCOp = MCOperand::createFPImm(Imm->getValueAPF().convertToFloat());
206 106 : else if (Imm->getType()->isDoubleTy())
207 106 : MCOp = MCOperand::createFPImm(Imm->getValueAPF().convertToDouble());
208 : else
209 0 : llvm_unreachable("unknown floating point immediate type");
210 : break;
211 : }
212 810 : case MachineOperand::MO_GlobalAddress:
213 : assert(MO.getTargetFlags() == WebAssemblyII::MO_NO_FLAG &&
214 : "WebAssembly does not use target flags on GlobalAddresses");
215 : MCOp = LowerSymbolOperand(GetGlobalAddressSymbol(MO), MO.getOffset(),
216 810 : MO.getGlobal()->getValueType()->isFunctionTy(),
217 1620 : false);
218 810 : break;
219 : case MachineOperand::MO_ExternalSymbol:
220 : // The target flag indicates whether this is a symbol for a
221 : // variable or a function.
222 : assert((MO.getTargetFlags() & ~WebAssemblyII::MO_SYMBOL_MASK) == 0 &&
223 : "WebAssembly uses only symbol flags on ExternalSymbols");
224 : MCOp = LowerSymbolOperand(
225 : GetExternalSymbolSymbol(MO), /*Offset=*/0,
226 376 : (MO.getTargetFlags() & WebAssemblyII::MO_SYMBOL_FUNCTION) != 0,
227 752 : (MO.getTargetFlags() & WebAssemblyII::MO_SYMBOL_GLOBAL) != 0);
228 376 : break;
229 : }
230 :
231 : OutMI.addOperand(MCOp);
232 : }
233 :
234 24888 : if (!WasmKeepRegisters)
235 3156 : removeRegisterOperands(MI, OutMI);
236 24888 : }
237 :
238 3156 : static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI) {
239 : // Remove all uses of stackified registers to bring the instruction format
240 : // into its final stack form used thruout MC, and transition opcodes to
241 : // their _S variant.
242 : // We do this seperate from the above code that still may need these
243 : // registers for e.g. call_indirect signatures.
244 : // See comments in lib/Target/WebAssembly/WebAssemblyInstrFormats.td for
245 : // details.
246 : // TODO: the code above creates new registers which are then removed here.
247 : // That code could be slightly simplified by not doing that, though maybe
248 : // it is simpler conceptually to keep the code above in "register mode"
249 : // until this transition point.
250 : // FIXME: we are not processing inline assembly, which contains register
251 : // operands, because it is used by later target generic code.
252 3156 : if (MI->isDebugInstr() || MI->isLabel() || MI->isInlineAsm())
253 : return;
254 :
255 : // Transform to _S instruction.
256 3156 : auto RegOpcode = OutMI.getOpcode();
257 3156 : auto StackOpcode = regInstructionToStackInstruction(RegOpcode);
258 : OutMI.setOpcode(StackOpcode);
259 :
260 : // Remove register operands.
261 8851 : for (auto I = OutMI.getNumOperands(); I; --I) {
262 5695 : auto &MO = OutMI.getOperand(I - 1);
263 5695 : if (MO.isReg()) {
264 : OutMI.erase(&MO);
265 : }
266 : }
267 : }
268 :
269 3156 : static unsigned regInstructionToStackInstruction(unsigned OpCode) {
270 : // For most opcodes, this function could have been implemented as "return
271 : // OpCode + 1", but since table-gen alphabetically sorts them, this cannot be
272 : // guaranteed (see e.g. BR and BR_IF). Instead we use a giant switch statement
273 : // generated by a custom TableGen backend (WebAssemblyStackifierEmitter.cpp)
274 : // that emits switch cases of the form
275 : //
276 : // case WebAssembly::RegisterInstr: return WebAssembly::StackInstr;
277 : //
278 : // for every pair of equivalent register and stack instructions.
279 3156 : switch (OpCode) {
280 0 : default:
281 0 : llvm_unreachable(
282 : "unknown WebAssembly instruction in WebAssemblyMCInstLower pass");
283 : #include "WebAssemblyGenStackifier.inc"
284 : }
285 : }
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