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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/STLExtras.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/MC/MCRegisterInfo.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/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;
// Implementation generated by tablegen.
uint64_t getBinaryCodeForInstr(const MCInst &MI,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const;
void encodeInstruction(const MCInst &MI, raw_ostream &OS,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const override;
public:
WebAssemblyMCCodeEmitter(const MCInstrInfo &MCII) : MCII(MCII) {}
};
} // end anonymous namespace
MCCodeEmitter *llvm::createWebAssemblyMCCodeEmitter(const MCInstrInfo &MCII) {
return new WebAssemblyMCCodeEmitter(MCII);
}
void WebAssemblyMCCodeEmitter::encodeInstruction(
const MCInst &MI, raw_ostream &OS, SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const {
uint64_t Start = OS.tell();
uint64_t Binary = getBinaryCodeForInstr(MI, Fixups, STI);
if (Binary <= UINT8_MAX) {
OS << uint8_t(Binary);
} else {
assert(Binary <= UINT16_MAX && "Several-byte opcodes not supported yet");
OS << uint8_t(Binary >> 8);
encodeULEB128(uint8_t(Binary), OS);
}
// 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.
if (MI.getOpcode() == WebAssembly::BR_TABLE_I32_S ||
MI.getOpcode() == WebAssembly::BR_TABLE_I64_S)
encodeULEB128(MI.getNumOperands() - 1, OS);
if (MI.getOpcode() == WebAssembly::BR_TABLE_I32 ||
MI.getOpcode() == WebAssembly::BR_TABLE_I64)
encodeULEB128(MI.getNumOperands() - 2, OS);
const MCInstrDesc &Desc = MCII.get(MI.getOpcode());
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.OpInfo[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(int64_t(MO.getImm()), OS);
break;
case WebAssembly::OPERAND_SIGNATURE:
OS << uint8_t(MO.getImm());
break;
case WebAssembly::OPERAND_VEC_I8IMM:
support::endian::write<uint8_t>(OS, MO.getImm(), support::little);
break;
case WebAssembly::OPERAND_VEC_I16IMM:
support::endian::write<uint16_t>(OS, MO.getImm(), support::little);
break;
case WebAssembly::OPERAND_VEC_I32IMM:
support::endian::write<uint32_t>(OS, MO.getImm(), support::little);
break;
case WebAssembly::OPERAND_VEC_I64IMM:
support::endian::write<uint64_t>(OS, MO.getImm(), support::little);
break;
case WebAssembly::OPERAND_GLOBAL:
llvm_unreachable("wasm globals should only be accessed symbolicly");
default:
encodeULEB128(uint64_t(MO.getImm()), OS);
}
} else {
encodeULEB128(uint64_t(MO.getImm()), OS);
}
} else if (MO.isFPImm()) {
const MCOperandInfo &Info = Desc.OpInfo[I];
if (Info.OperandType == WebAssembly::OPERAND_F32IMM) {
// TODO: MC converts all floating point immediate operands to double.
// This is fine for numeric values, but may cause NaNs to change bits.
auto F = float(MO.getFPImm());
support::endian::write<float>(OS, F, support::little);
} else {
assert(Info.OperandType == WebAssembly::OPERAND_F64IMM);
double D = MO.getFPImm();
support::endian::write<double>(OS, D, support::little);
}
} else if (MO.isExpr()) {
const MCOperandInfo &Info = Desc.OpInfo[I];
llvm::MCFixupKind FixupKind;
size_t PaddedSize = 5;
switch (Info.OperandType) {
case WebAssembly::OPERAND_I32IMM:
FixupKind = MCFixupKind(WebAssembly::fixup_sleb128_i32);
break;
case WebAssembly::OPERAND_I64IMM:
FixupKind = MCFixupKind(WebAssembly::fixup_sleb128_i64);
PaddedSize = 10;
break;
case WebAssembly::OPERAND_FUNCTION32:
case WebAssembly::OPERAND_OFFSET32:
case WebAssembly::OPERAND_SIGNATURE:
case WebAssembly::OPERAND_TYPEINDEX:
case WebAssembly::OPERAND_GLOBAL:
case WebAssembly::OPERAND_EVENT:
FixupKind = MCFixupKind(WebAssembly::fixup_uleb128_i32);
break;
default:
llvm_unreachable("unexpected symbolic operand kind");
}
Fixups.push_back(MCFixup::create(OS.tell() - Start, MO.getExpr(),
FixupKind, MI.getLoc()));
++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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