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//=- WebAssemblyMCCodeEmitter.cpp - Convert WebAssembly code to machine code -//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file implements the WebAssemblyMCCodeEmitter class.
///
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/WebAssemblyFixupKinds.h"
#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/EndianStream.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/SMLoc.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#define DEBUG_TYPE "mccodeemitter"
STATISTIC(MCNumEmitted, "Number of MC instructions emitted.");
STATISTIC(MCNumFixups, "Number of MC fixups created.");
namespace {
class WebAssemblyMCCodeEmitter final : public MCCodeEmitter {
const MCInstrInfo &MCII;
MCContext &Ctx;
// Implementation generated by tablegen.
uint64_t getBinaryCodeForInstr(const MCInst &MI,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const;
void encodeInstruction(const MCInst &MI, SmallVectorImpl<char> &CB,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const override;
public:
WebAssemblyMCCodeEmitter(const MCInstrInfo &MCII, MCContext &Ctx)
: MCII(MCII), Ctx{Ctx} {}
};
} // end anonymous namespace
MCCodeEmitter *llvm::createWebAssemblyMCCodeEmitter(const MCInstrInfo &MCII,
MCContext &Ctx) {
return new WebAssemblyMCCodeEmitter(MCII, Ctx);
}
void WebAssemblyMCCodeEmitter::encodeInstruction(
const MCInst &MI, SmallVectorImpl<char> &CB,
SmallVectorImpl<MCFixup> &Fixups, const MCSubtargetInfo &STI) const {
raw_svector_ostream OS(CB);
uint64_t Start = OS.tell();
uint64_t Binary = getBinaryCodeForInstr(MI, Fixups, STI);
if (Binary < (1 << 8)) {
OS << uint8_t(Binary);
} else if (Binary < (1 << 16)) {
OS << uint8_t(Binary >> 8);
encodeULEB128(uint8_t(Binary), OS);
} else if (Binary < (1 << 24)) {
OS << uint8_t(Binary >> 16);
encodeULEB128(uint16_t(Binary), OS);
} else {
llvm_unreachable("Very large (prefix + 3 byte) opcodes not supported");
}
// For br_table instructions, encode the size of the table. In the MCInst,
// there's an index operand (if not a stack instruction), one operand for
// each table entry, and the default operand.
unsigned Opcode = MI.getOpcode();
if (Opcode == WebAssembly::BR_TABLE_I32_S ||
Opcode == WebAssembly::BR_TABLE_I64_S)
encodeULEB128(MI.getNumOperands() - 1, OS);
if (Opcode == WebAssembly::BR_TABLE_I32 ||
Opcode == WebAssembly::BR_TABLE_I64)
encodeULEB128(MI.getNumOperands() - 2, OS);
const MCInstrDesc &Desc = MCII.get(Opcode);
for (unsigned I = 0, E = MI.getNumOperands(); I < E; ++I) {
const MCOperand &MO = MI.getOperand(I);
if (MO.isReg()) {
/* nothing to encode */
} else if (MO.isImm()) {
if (I < Desc.getNumOperands()) {
const MCOperandInfo &Info = Desc.operands()[I];
LLVM_DEBUG(dbgs() << "Encoding immediate: type="
<< int(Info.OperandType) << "\n");
switch (Info.OperandType) {
case WebAssembly::OPERAND_I32IMM:
encodeSLEB128(int32_t(MO.getImm()), OS);
break;
case WebAssembly::OPERAND_OFFSET32:
encodeULEB128(uint32_t(MO.getImm()), OS);
break;
case WebAssembly::OPERAND_I64IMM:
encodeSLEB128(MO.getImm(), OS);
break;
case WebAssembly::OPERAND_SIGNATURE:
case WebAssembly::OPERAND_VEC_I8IMM:
support::endian::write<uint8_t>(OS, MO.getImm(),
llvm::endianness::little);
break;
case WebAssembly::OPERAND_VEC_I16IMM:
support::endian::write<uint16_t>(OS, MO.getImm(),
llvm::endianness::little);
break;
case WebAssembly::OPERAND_VEC_I32IMM:
support::endian::write<uint32_t>(OS, MO.getImm(),
llvm::endianness::little);
break;
case WebAssembly::OPERAND_VEC_I64IMM:
support::endian::write<uint64_t>(OS, MO.getImm(),
llvm::endianness::little);
break;
case WebAssembly::OPERAND_GLOBAL:
Ctx.reportError(
SMLoc(),
Twine("Wasm globals should only be accessed symbolically!"));
break;
default:
encodeULEB128(uint64_t(MO.getImm()), OS);
}
} else {
// Variadic immediate operands are br_table's destination operands or
// try_table's operands (# of catch clauses, catch sub-opcodes, or catch
// clause destinations)
assert(WebAssembly::isBrTable(Opcode) ||
Opcode == WebAssembly::TRY_TABLE_S);
encodeULEB128(uint32_t(MO.getImm()), OS);
}
} else if (MO.isSFPImm()) {
uint32_t F = MO.getSFPImm();
support::endian::write<uint32_t>(OS, F, llvm::endianness::little);
} else if (MO.isDFPImm()) {
uint64_t D = MO.getDFPImm();
support::endian::write<uint64_t>(OS, D, llvm::endianness::little);
} else if (MO.isExpr()) {
llvm::MCFixupKind FixupKind;
size_t PaddedSize = 5;
if (I < Desc.getNumOperands()) {
const MCOperandInfo &Info = Desc.operands()[I];
switch (Info.OperandType) {
case WebAssembly::OPERAND_I32IMM:
FixupKind = WebAssembly::fixup_sleb128_i32;
break;
case WebAssembly::OPERAND_I64IMM:
FixupKind = WebAssembly::fixup_sleb128_i64;
PaddedSize = 10;
break;
case WebAssembly::OPERAND_FUNCTION32:
case WebAssembly::OPERAND_TABLE:
case WebAssembly::OPERAND_OFFSET32:
case WebAssembly::OPERAND_SIGNATURE:
case WebAssembly::OPERAND_TYPEINDEX:
case WebAssembly::OPERAND_GLOBAL:
case WebAssembly::OPERAND_TAG:
FixupKind = WebAssembly::fixup_uleb128_i32;
break;
case WebAssembly::OPERAND_OFFSET64:
FixupKind = WebAssembly::fixup_uleb128_i64;
PaddedSize = 10;
break;
default:
llvm_unreachable("unexpected symbolic operand kind");
}
} else {
// Variadic expr operands are try_table's catch/catch_ref clauses' tags.
assert(Opcode == WebAssembly::TRY_TABLE_S);
FixupKind = WebAssembly::fixup_uleb128_i32;
}
Fixups.push_back(
MCFixup::create(OS.tell() - Start, MO.getExpr(), FixupKind));
++MCNumFixups;
encodeULEB128(0, OS, PaddedSize);
} else {
llvm_unreachable("unexpected operand kind");
}
}
++MCNumEmitted; // Keep track of the # of mi's emitted.
}
#include "WebAssemblyGenMCCodeEmitter.inc"
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