1//=- WebAssemblyMCCodeEmitter.cpp - Convert WebAssembly code to machine code -//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8///
9/// \file
10/// This file implements the WebAssemblyMCCodeEmitter class.
11///
12//===----------------------------------------------------------------------===//
13
14#include "MCTargetDesc/WebAssemblyFixupKinds.h"
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/MCContext.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/Debug.h"
27#include "llvm/Support/EndianStream.h"
28#include "llvm/Support/LEB128.h"
29#include "llvm/Support/SMLoc.h"
30#include "llvm/Support/raw_ostream.h"
31
32using namespace llvm;
33
34#define DEBUG_TYPE "mccodeemitter"
35
36STATISTIC(MCNumEmitted, "Number of MC instructions emitted.");
37STATISTIC(MCNumFixups, "Number of MC fixups created.");
38
39namespace {
40class WebAssemblyMCCodeEmitter final : public MCCodeEmitter {
41 const MCInstrInfo &MCII;
42 MCContext &Ctx;
43 // Implementation generated by tablegen.
44 uint64_t getBinaryCodeForInstr(const MCInst &MI,
45 SmallVectorImpl<MCFixup> &Fixups,
46 const MCSubtargetInfo &STI) const;
47
48 void encodeInstruction(const MCInst &MI, SmallVectorImpl<char> &CB,
49 SmallVectorImpl<MCFixup> &Fixups,
50 const MCSubtargetInfo &STI) const override;
51
52public:
53 WebAssemblyMCCodeEmitter(const MCInstrInfo &MCII, MCContext &Ctx)
54 : MCII(MCII), Ctx{Ctx} {}
55};
56} // end anonymous namespace
57
58MCCodeEmitter *llvm::createWebAssemblyMCCodeEmitter(const MCInstrInfo &MCII,
59 MCContext &Ctx) {
60 return new WebAssemblyMCCodeEmitter(MCII, Ctx);
61}
62
63void WebAssemblyMCCodeEmitter::encodeInstruction(
64 const MCInst &MI, SmallVectorImpl<char> &CB,
65 SmallVectorImpl<MCFixup> &Fixups, const MCSubtargetInfo &STI) const {
66 raw_svector_ostream OS(CB);
67 uint64_t Start = OS.tell();
68
69 uint64_t Binary = getBinaryCodeForInstr(MI, Fixups, STI);
70 if (Binary < (1 << 8)) {
71 OS << uint8_t(Binary);
72 } else if (Binary < (1 << 16)) {
73 OS << uint8_t(Binary >> 8);
74 encodeULEB128(Value: uint8_t(Binary), OS);
75 } else if (Binary < (1 << 24)) {
76 OS << uint8_t(Binary >> 16);
77 encodeULEB128(Value: uint16_t(Binary), OS);
78 } else {
79 llvm_unreachable("Very large (prefix + 3 byte) opcodes not supported");
80 }
81
82 // For br_table instructions, encode the size of the table. In the MCInst,
83 // there's an index operand (if not a stack instruction), one operand for
84 // each table entry, and the default operand.
85 if (MI.getOpcode() == WebAssembly::BR_TABLE_I32_S ||
86 MI.getOpcode() == WebAssembly::BR_TABLE_I64_S)
87 encodeULEB128(Value: MI.getNumOperands() - 1, OS);
88 if (MI.getOpcode() == WebAssembly::BR_TABLE_I32 ||
89 MI.getOpcode() == WebAssembly::BR_TABLE_I64)
90 encodeULEB128(Value: MI.getNumOperands() - 2, OS);
91
92 const MCInstrDesc &Desc = MCII.get(Opcode: MI.getOpcode());
93 for (unsigned I = 0, E = MI.getNumOperands(); I < E; ++I) {
94 const MCOperand &MO = MI.getOperand(i: I);
95 if (MO.isReg()) {
96 /* nothing to encode */
97
98 } else if (MO.isImm()) {
99 if (I < Desc.getNumOperands()) {
100 const MCOperandInfo &Info = Desc.operands()[I];
101 LLVM_DEBUG(dbgs() << "Encoding immediate: type="
102 << int(Info.OperandType) << "\n");
103 switch (Info.OperandType) {
104 case WebAssembly::OPERAND_I32IMM:
105 encodeSLEB128(Value: int32_t(MO.getImm()), OS);
106 break;
107 case WebAssembly::OPERAND_OFFSET32:
108 encodeULEB128(Value: uint32_t(MO.getImm()), OS);
109 break;
110 case WebAssembly::OPERAND_I64IMM:
111 encodeSLEB128(Value: int64_t(MO.getImm()), OS);
112 break;
113 case WebAssembly::OPERAND_SIGNATURE:
114 case WebAssembly::OPERAND_VEC_I8IMM:
115 support::endian::write<uint8_t>(os&: OS, value: MO.getImm(),
116 endian: llvm::endianness::little);
117 break;
118 case WebAssembly::OPERAND_VEC_I16IMM:
119 support::endian::write<uint16_t>(os&: OS, value: MO.getImm(),
120 endian: llvm::endianness::little);
121 break;
122 case WebAssembly::OPERAND_VEC_I32IMM:
123 support::endian::write<uint32_t>(os&: OS, value: MO.getImm(),
124 endian: llvm::endianness::little);
125 break;
126 case WebAssembly::OPERAND_VEC_I64IMM:
127 support::endian::write<uint64_t>(os&: OS, value: MO.getImm(),
128 endian: llvm::endianness::little);
129 break;
130 case WebAssembly::OPERAND_GLOBAL:
131 Ctx.reportError(
132 L: SMLoc(),
133 Msg: Twine("Wasm globals should only be accessed symbolically!"));
134 break;
135 default:
136 encodeULEB128(Value: uint64_t(MO.getImm()), OS);
137 }
138 } else {
139 encodeULEB128(Value: uint64_t(MO.getImm()), OS);
140 }
141
142 } else if (MO.isSFPImm()) {
143 uint32_t F = MO.getSFPImm();
144 support::endian::write<uint32_t>(os&: OS, value: F, endian: llvm::endianness::little);
145 } else if (MO.isDFPImm()) {
146 uint64_t D = MO.getDFPImm();
147 support::endian::write<uint64_t>(os&: OS, value: D, endian: llvm::endianness::little);
148 } else if (MO.isExpr()) {
149 const MCOperandInfo &Info = Desc.operands()[I];
150 llvm::MCFixupKind FixupKind;
151 size_t PaddedSize = 5;
152 switch (Info.OperandType) {
153 case WebAssembly::OPERAND_I32IMM:
154 FixupKind = MCFixupKind(WebAssembly::fixup_sleb128_i32);
155 break;
156 case WebAssembly::OPERAND_I64IMM:
157 FixupKind = MCFixupKind(WebAssembly::fixup_sleb128_i64);
158 PaddedSize = 10;
159 break;
160 case WebAssembly::OPERAND_FUNCTION32:
161 case WebAssembly::OPERAND_TABLE:
162 case WebAssembly::OPERAND_OFFSET32:
163 case WebAssembly::OPERAND_SIGNATURE:
164 case WebAssembly::OPERAND_TYPEINDEX:
165 case WebAssembly::OPERAND_GLOBAL:
166 case WebAssembly::OPERAND_TAG:
167 FixupKind = MCFixupKind(WebAssembly::fixup_uleb128_i32);
168 break;
169 case WebAssembly::OPERAND_OFFSET64:
170 FixupKind = MCFixupKind(WebAssembly::fixup_uleb128_i64);
171 PaddedSize = 10;
172 break;
173 default:
174 llvm_unreachable("unexpected symbolic operand kind");
175 }
176 Fixups.push_back(Elt: MCFixup::create(Offset: OS.tell() - Start, Value: MO.getExpr(),
177 Kind: FixupKind, Loc: MI.getLoc()));
178 ++MCNumFixups;
179 encodeULEB128(Value: 0, OS, PadTo: PaddedSize);
180 } else {
181 llvm_unreachable("unexpected operand kind");
182 }
183 }
184
185 ++MCNumEmitted; // Keep track of the # of mi's emitted.
186}
187
188#include "WebAssemblyGenMCCodeEmitter.inc"
189