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//=- WebAssemblyMCCodeEmitter.cpp - Convert WebAssembly code to machine code -//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// \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)
<< uint8_t(Binary);
}
// For br_table instructions, encode the size of the table. In the MCInst,
// there's an index operand, one operand for each table entry, and the
// default operand.
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()) {
assert(Desc.TSFlags == 0 &&
"WebAssembly non-variable_ops don't use TSFlags");
const MCOperandInfo &Info = Desc.OpInfo[i];
LLVM_DEBUG(dbgs() << "Encoding immediate: type="
<< int(Info.OperandType) << "\n");
if (Info.OperandType == WebAssembly::OPERAND_I32IMM) {
encodeSLEB128(int32_t(MO.getImm()), OS);
} else if (Info.OperandType == WebAssembly::OPERAND_OFFSET32) {
encodeULEB128(uint32_t(MO.getImm()), OS);
} else if (Info.OperandType == WebAssembly::OPERAND_I64IMM) {
encodeSLEB128(int64_t(MO.getImm()), OS);
} else if (Info.OperandType == WebAssembly::OPERAND_GLOBAL) {
llvm_unreachable("wasm globals should only be accessed symbolicly");
} else if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) {
OS << uint8_t(MO.getImm());
} else {
encodeULEB128(uint64_t(MO.getImm()), OS);
}
} else {
assert(Desc.TSFlags == (WebAssemblyII::VariableOpIsImmediate |
WebAssemblyII::VariableOpImmediateIsLabel));
encodeULEB128(uint64_t(MO.getImm()), OS);
}
} else if (MO.isFPImm()) {
assert(i < Desc.getNumOperands() &&
"Unexpected floating-point immediate as a non-fixed operand");
assert(Desc.TSFlags == 0 &&
"WebAssembly variable_ops floating point ops don't use TSFlags");
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.
float 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;
if (Info.OperandType == WebAssembly::OPERAND_I32IMM) {
FixupKind = MCFixupKind(WebAssembly::fixup_code_sleb128_i32);
} else if (Info.OperandType == WebAssembly::OPERAND_I64IMM) {
FixupKind = MCFixupKind(WebAssembly::fixup_code_sleb128_i64);
PaddedSize = 10;
} else if (Info.OperandType == WebAssembly::OPERAND_FUNCTION32 ||
Info.OperandType == WebAssembly::OPERAND_OFFSET32 ||
Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) {
FixupKind = MCFixupKind(WebAssembly::fixup_code_uleb128_i32);
} else if (Info.OperandType == WebAssembly::OPERAND_GLOBAL) {
FixupKind = MCFixupKind(WebAssembly::fixup_code_global_index);
} else {
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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