1 //=- WebAssemblyMCCodeEmitter.cpp - Convert WebAssembly code to machine code -//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 /// \brief This file implements the WebAssemblyMCCodeEmitter class.
13 //===----------------------------------------------------------------------===//
15 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
16 #include "MCTargetDesc/WebAssemblyFixupKinds.h"
17 #include "llvm/ADT/STLExtras.h"
18 #include "llvm/ADT/Statistic.h"
19 #include "llvm/MC/MCCodeEmitter.h"
20 #include "llvm/MC/MCFixup.h"
21 #include "llvm/MC/MCInst.h"
22 #include "llvm/MC/MCInstrInfo.h"
23 #include "llvm/MC/MCRegisterInfo.h"
24 #include "llvm/MC/MCSubtargetInfo.h"
25 #include "llvm/MC/MCSymbol.h"
26 #include "llvm/Support/EndianStream.h"
27 #include "llvm/Support/LEB128.h"
28 #include "llvm/Support/raw_ostream.h"
31 #define DEBUG_TYPE "mccodeemitter"
33 STATISTIC(MCNumEmitted, "Number of MC instructions emitted.");
34 STATISTIC(MCNumFixups, "Number of MC fixups created.");
37 class WebAssemblyMCCodeEmitter final : public MCCodeEmitter {
38 const MCInstrInfo &MCII;
41 // Implementation generated by tablegen.
42 uint64_t getBinaryCodeForInstr(const MCInst &MI,
43 SmallVectorImpl<MCFixup> &Fixups,
44 const MCSubtargetInfo &STI) const;
46 void encodeInstruction(const MCInst &MI, raw_ostream &OS,
47 SmallVectorImpl<MCFixup> &Fixups,
48 const MCSubtargetInfo &STI) const override;
51 WebAssemblyMCCodeEmitter(const MCInstrInfo &mcii, MCContext &ctx)
52 : MCII(mcii), Ctx(ctx) {}
54 } // end anonymous namespace
56 MCCodeEmitter *llvm::createWebAssemblyMCCodeEmitter(const MCInstrInfo &MCII,
58 return new WebAssemblyMCCodeEmitter(MCII, Ctx);
61 void WebAssemblyMCCodeEmitter::encodeInstruction(
62 const MCInst &MI, raw_ostream &OS, SmallVectorImpl<MCFixup> &Fixups,
63 const MCSubtargetInfo &STI) const {
64 uint64_t Start = OS.tell();
66 uint64_t Binary = getBinaryCodeForInstr(MI, Fixups, STI);
67 assert(Binary < UINT8_MAX && "Multi-byte opcodes not supported yet");
68 OS << uint8_t(Binary);
70 // For br_table instructions, encode the size of the table. In the MCInst,
71 // there's an index operand, one operand for each table entry, and the
73 if (MI.getOpcode() == WebAssembly::BR_TABLE_I32 ||
74 MI.getOpcode() == WebAssembly::BR_TABLE_I64)
75 encodeULEB128(MI.getNumOperands() - 2, OS);
77 const MCInstrDesc &Desc = MCII.get(MI.getOpcode());
78 for (unsigned i = 0, e = MI.getNumOperands(); i < e; ++i) {
79 const MCOperand &MO = MI.getOperand(i);
81 /* nothing to encode */
82 } else if (MO.isImm()) {
83 if (i < Desc.getNumOperands()) {
84 assert(Desc.TSFlags == 0 &&
85 "WebAssembly non-variable_ops don't use TSFlags");
86 const MCOperandInfo &Info = Desc.OpInfo[i];
87 if (Info.OperandType == WebAssembly::OPERAND_I32IMM) {
88 encodeSLEB128(int32_t(MO.getImm()), OS);
89 } else if (Info.OperandType == WebAssembly::OPERAND_I64IMM) {
90 encodeSLEB128(int64_t(MO.getImm()), OS);
91 } else if (Info.OperandType == WebAssembly::OPERAND_GLOBAL) {
92 Fixups.push_back(MCFixup::create(
93 OS.tell() - Start, MCConstantExpr::create(MO.getImm(), Ctx),
94 MCFixupKind(WebAssembly::fixup_code_global_index), MI.getLoc()));
96 encodeULEB128(uint64_t(MO.getImm()), OS);
97 } else if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) {
98 encodeSLEB128(int64_t(MO.getImm()), OS);
100 encodeULEB128(uint64_t(MO.getImm()), OS);
103 assert(Desc.TSFlags == (WebAssemblyII::VariableOpIsImmediate |
104 WebAssemblyII::VariableOpImmediateIsLabel));
105 encodeULEB128(uint64_t(MO.getImm()), OS);
107 } else if (MO.isFPImm()) {
108 assert(i < Desc.getNumOperands() &&
109 "Unexpected floating-point immediate as a non-fixed operand");
110 assert(Desc.TSFlags == 0 &&
111 "WebAssembly variable_ops floating point ops don't use TSFlags");
112 const MCOperandInfo &Info = Desc.OpInfo[i];
113 if (Info.OperandType == WebAssembly::OPERAND_F32IMM) {
114 // TODO: MC converts all floating point immediate operands to double.
115 // This is fine for numeric values, but may cause NaNs to change bits.
116 float f = float(MO.getFPImm());
117 support::endian::Writer<support::little>(OS).write<float>(f);
119 assert(Info.OperandType == WebAssembly::OPERAND_F64IMM);
120 double d = MO.getFPImm();
121 support::endian::Writer<support::little>(OS).write<double>(d);
123 } else if (MO.isExpr()) {
124 const MCOperandInfo &Info = Desc.OpInfo[i];
125 llvm::MCFixupKind FixupKind;
127 if (Info.OperandType == WebAssembly::OPERAND_I32IMM) {
128 FixupKind = MCFixupKind(WebAssembly::fixup_code_sleb128_i32);
130 } else if (Info.OperandType == WebAssembly::OPERAND_I64IMM) {
131 FixupKind = MCFixupKind(WebAssembly::fixup_code_sleb128_i64);
133 } else if (Info.OperandType == WebAssembly::OPERAND_FUNCTION32 ||
134 Info.OperandType == WebAssembly::OPERAND_OFFSET32 ||
135 Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) {
136 FixupKind = MCFixupKind(WebAssembly::fixup_code_uleb128_i32);
139 llvm_unreachable("unexpected symbolic operand kind");
141 Fixups.push_back(MCFixup::create(
142 OS.tell() - Start, MO.getExpr(),
143 FixupKind, MI.getLoc()));
145 encodeULEB128(0, OS, PaddedSize - 1);
147 llvm_unreachable("unexpected operand kind");
151 ++MCNumEmitted; // Keep track of the # of mi's emitted.
154 #include "WebAssemblyGenMCCodeEmitter.inc"