1 //=- WebAssemblyMCCodeEmitter.cpp - Convert WebAssembly code to machine code -//
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 implements the WebAssemblyMCCodeEmitter class.
12 ///
13 //===----------------------------------------------------------------------===//
14 
15 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
16 #include "llvm/ADT/STLExtras.h"
17 #include "llvm/ADT/Statistic.h"
18 #include "llvm/MC/MCCodeEmitter.h"
19 #include "llvm/MC/MCFixup.h"
20 #include "llvm/MC/MCInst.h"
21 #include "llvm/MC/MCInstrInfo.h"
22 #include "llvm/MC/MCRegisterInfo.h"
23 #include "llvm/MC/MCSubtargetInfo.h"
24 #include "llvm/MC/MCSymbol.h"
25 #include "llvm/Support/EndianStream.h"
26 #include "llvm/Support/LEB128.h"
27 #include "llvm/Support/raw_ostream.h"
28 using namespace llvm;
29 
30 #define DEBUG_TYPE "mccodeemitter"
31 
32 STATISTIC(MCNumEmitted, "Number of MC instructions emitted.");
33 STATISTIC(MCNumFixups, "Number of MC fixups created.");
34 
35 namespace {
36 class WebAssemblyMCCodeEmitter final : public MCCodeEmitter {
37   const MCInstrInfo &MCII;
38 
39   // Implementation generated by tablegen.
40   uint64_t getBinaryCodeForInstr(const MCInst &MI,
41                                  SmallVectorImpl<MCFixup> &Fixups,
42                                  const MCSubtargetInfo &STI) const;
43 
44   void encodeInstruction(const MCInst &MI, raw_ostream &OS,
45                          SmallVectorImpl<MCFixup> &Fixups,
46                          const MCSubtargetInfo &STI) const override;
47 
48 public:
49   WebAssemblyMCCodeEmitter(const MCInstrInfo &mcii) : MCII(mcii) {}
50 };
51 } // end anonymous namespace
52 
53 MCCodeEmitter *llvm::createWebAssemblyMCCodeEmitter(const MCInstrInfo &MCII) {
54   return new WebAssemblyMCCodeEmitter(MCII);
55 }
56 
57 void WebAssemblyMCCodeEmitter::encodeInstruction(
58     const MCInst &MI, raw_ostream &OS, SmallVectorImpl<MCFixup> &Fixups,
59     const MCSubtargetInfo &STI) const {
60   uint64_t Start = OS.tell();
61 
62   uint64_t Binary = getBinaryCodeForInstr(MI, Fixups, STI);
63   assert(Binary < UINT8_MAX && "Multi-byte opcodes not supported yet");
64   OS << uint8_t(Binary);
65 
66   const MCInstrDesc &Desc = MCII.get(MI.getOpcode());
67   for (unsigned i = 0, e = MI.getNumOperands(); i < e; ++i) {
68     const MCOperand &MO = MI.getOperand(i);
69     if (MO.isReg()) {
70       /* nothing to encode */
71     } else if (MO.isImm()) {
72       if (i < Desc.getNumOperands()) {
73         assert(Desc.TSFlags == 0 &&
74                "WebAssembly non-variable_ops don't use TSFlags");
75         const MCOperandInfo &Info = Desc.OpInfo[i];
76         if (Info.OperandType == WebAssembly::OPERAND_I32IMM) {
77           encodeSLEB128(int32_t(MO.getImm()), OS);
78         } else if (Info.OperandType == WebAssembly::OPERAND_I64IMM) {
79           encodeSLEB128(int64_t(MO.getImm()), OS);
80         } else {
81           encodeULEB128(uint64_t(MO.getImm()), OS);
82         }
83       } else {
84         assert(Desc.TSFlags == (WebAssemblyII::VariableOpIsImmediate |
85                                 WebAssemblyII::VariableOpImmediateIsLabel));
86         encodeULEB128(uint64_t(MO.getImm()), OS);
87       }
88     } else if (MO.isFPImm()) {
89       assert(i < Desc.getNumOperands() &&
90              "Unexpected floating-point immediate as a non-fixed operand");
91       assert(Desc.TSFlags == 0 &&
92              "WebAssembly variable_ops floating point ops don't use TSFlags");
93       const MCOperandInfo &Info = Desc.OpInfo[i];
94       if (Info.OperandType == WebAssembly::OPERAND_F32IMM) {
95         // TODO: MC converts all floating point immediate operands to double.
96         // This is fine for numeric values, but may cause NaNs to change bits.
97         float f = float(MO.getFPImm());
98         support::endian::Writer<support::little>(OS).write<float>(f);
99       } else {
100         assert(Info.OperandType == WebAssembly::OPERAND_F64IMM);
101         double d = MO.getFPImm();
102         support::endian::Writer<support::little>(OS).write<double>(d);
103       }
104     } else if (MO.isExpr()) {
105       Fixups.push_back(MCFixup::create(
106           OS.tell() - Start, MO.getExpr(),
107           STI.getTargetTriple().isArch64Bit() ? FK_Data_8 : FK_Data_4,
108           MI.getLoc()));
109       ++MCNumFixups;
110       encodeULEB128(STI.getTargetTriple().isArch64Bit() ? UINT64_MAX
111                                                         : uint64_t(UINT32_MAX),
112                     OS);
113     } else {
114       llvm_unreachable("unexpected operand kind");
115     }
116   }
117 
118   ++MCNumEmitted; // Keep track of the # of mi's emitted.
119 }
120 
121 #include "WebAssemblyGenMCCodeEmitter.inc"
122