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llvm-mirror/lib/Target/X86/X86CodeEmitter.cpp
Chris Lattner f4c8575535 There is no reason to emit function stubs for direct calls. 
llvm-svn: 18082
2004-11-21 03:46:06 +00:00

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//===-- X86/X86CodeEmitter.cpp - Convert X86 code to machine code ---------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the pass that transforms the X86 machine instructions into
// relocatable machine code.
//
//===----------------------------------------------------------------------===//
#include "X86TargetMachine.h"
#include "X86Relocations.h"
#include "X86.h"
#include "llvm/PassManager.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Function.h"
#include "llvm/ADT/Statistic.h"
using namespace llvm;
namespace {
Statistic<>
NumEmitted("x86-emitter", "Number of machine instructions emitted");
}
namespace {
class Emitter : public MachineFunctionPass {
const X86InstrInfo *II;
MachineCodeEmitter &MCE;
std::map<const MachineBasicBlock*, unsigned> BasicBlockAddrs;
std::vector<std::pair<const MachineBasicBlock *, unsigned> > BBRefs;
public:
explicit Emitter(MachineCodeEmitter &mce) : II(0), MCE(mce) {}
Emitter(MachineCodeEmitter &mce, const X86InstrInfo& ii)
: II(&ii), MCE(mce) {}
bool runOnMachineFunction(MachineFunction &MF);
virtual const char *getPassName() const {
return "X86 Machine Code Emitter";
}
void emitInstruction(const MachineInstr &MI);
private:
void emitBasicBlock(const MachineBasicBlock &MBB);
void emitPCRelativeBlockAddress(const MachineBasicBlock *BB);
void emitPCRelativeValue(unsigned Address);
void emitGlobalAddressForCall(GlobalValue *GV);
void emitGlobalAddressForPtr(GlobalValue *GV, int Disp = 0);
void emitExternalSymbolAddress(const char *ES, bool isPCRelative);
void emitRegModRMByte(unsigned ModRMReg, unsigned RegOpcodeField);
void emitSIBByte(unsigned SS, unsigned Index, unsigned Base);
void emitConstant(unsigned Val, unsigned Size);
void emitMemModRMByte(const MachineInstr &MI,
unsigned Op, unsigned RegOpcodeField);
};
}
/// addPassesToEmitMachineCode - Add passes to the specified pass manager to get
/// machine code emitted. This uses a MachineCodeEmitter object to handle
/// actually outputting the machine code and resolving things like the address
/// of functions. This method should returns true if machine code emission is
/// not supported.
///
bool X86TargetMachine::addPassesToEmitMachineCode(FunctionPassManager &PM,
MachineCodeEmitter &MCE) {
PM.add(new Emitter(MCE));
// Delete machine code for this function
PM.add(createMachineCodeDeleter());
return false;
}
bool Emitter::runOnMachineFunction(MachineFunction &MF) {
II = ((X86TargetMachine&)MF.getTarget()).getInstrInfo();
MCE.startFunction(MF);
MCE.emitConstantPool(MF.getConstantPool());
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
emitBasicBlock(*I);
MCE.finishFunction(MF);
// Resolve all forward branches now...
for (unsigned i = 0, e = BBRefs.size(); i != e; ++i) {
unsigned Location = BasicBlockAddrs[BBRefs[i].first];
unsigned Ref = BBRefs[i].second;
MCE.emitWordAt(Location-Ref-4, (unsigned*)(intptr_t)Ref);
}
BBRefs.clear();
BasicBlockAddrs.clear();
return false;
}
void Emitter::emitBasicBlock(const MachineBasicBlock &MBB) {
if (uint64_t Addr = MCE.getCurrentPCValue())
BasicBlockAddrs[&MBB] = Addr;
for (MachineBasicBlock::const_iterator I = MBB.begin(), E = MBB.end();
I != E; ++I)
emitInstruction(*I);
}
/// emitPCRelativeValue - Emit a 32-bit PC relative address.
///
void Emitter::emitPCRelativeValue(unsigned Address) {
MCE.emitWord(Address-MCE.getCurrentPCValue()-4);
}
/// emitPCRelativeBlockAddress - This method emits the PC relative address of
/// the specified basic block, or if the basic block hasn't been emitted yet
/// (because this is a forward branch), it keeps track of the information
/// necessary to resolve this address later (and emits a dummy value).
///
void Emitter::emitPCRelativeBlockAddress(const MachineBasicBlock *MBB) {
// If this is a backwards branch, we already know the address of the target,
// so just emit the value.
std::map<const MachineBasicBlock*, unsigned>::iterator I =
BasicBlockAddrs.find(MBB);
if (I != BasicBlockAddrs.end()) {
emitPCRelativeValue(I->second);
} else {
// Otherwise, remember where this reference was and where it is to so we can
// deal with it later.
BBRefs.push_back(std::make_pair(MBB, MCE.getCurrentPCValue()));
MCE.emitWord(0);
}
}
/// emitGlobalAddressForCall - Emit the specified address to the code stream
/// assuming this is part of a function call, which is PC relative.
///
void Emitter::emitGlobalAddressForCall(GlobalValue *GV) {
MCE.addRelocation(MachineRelocation(MCE.getCurrentPCOffset(),
X86::reloc_pcrel_word, GV, 0, true));
MCE.emitWord(0);
}
/// emitGlobalAddress - Emit the specified address to the code stream assuming
/// this is part of a "take the address of a global" instruction, which is not
/// PC relative.
///
void Emitter::emitGlobalAddressForPtr(GlobalValue *GV, int Disp /* = 0 */) {
MCE.addRelocation(MachineRelocation(MCE.getCurrentPCOffset(),
X86::reloc_absolute_word, GV));
MCE.emitWord(Disp); // The relocated value will be added to the displacement
}
/// emitExternalSymbolAddress - Arrange for the address of an external symbol to
/// be emitted to the current location in the function, and allow it to be PC
/// relative.
void Emitter::emitExternalSymbolAddress(const char *ES, bool isPCRelative) {
MCE.addRelocation(MachineRelocation(MCE.getCurrentPCOffset(),
isPCRelative ? X86::reloc_pcrel_word : X86::reloc_absolute_word, ES));
MCE.emitWord(0);
}
/// N86 namespace - Native X86 Register numbers... used by X86 backend.
///
namespace N86 {
enum {
EAX = 0, ECX = 1, EDX = 2, EBX = 3, ESP = 4, EBP = 5, ESI = 6, EDI = 7
};
}
// getX86RegNum - This function maps LLVM register identifiers to their X86
// specific numbering, which is used in various places encoding instructions.
//
static unsigned getX86RegNum(unsigned RegNo) {
switch(RegNo) {
case X86::EAX: case X86::AX: case X86::AL: return N86::EAX;
case X86::ECX: case X86::CX: case X86::CL: return N86::ECX;
case X86::EDX: case X86::DX: case X86::DL: return N86::EDX;
case X86::EBX: case X86::BX: case X86::BL: return N86::EBX;
case X86::ESP: case X86::SP: case X86::AH: return N86::ESP;
case X86::EBP: case X86::BP: case X86::CH: return N86::EBP;
case X86::ESI: case X86::SI: case X86::DH: return N86::ESI;
case X86::EDI: case X86::DI: case X86::BH: return N86::EDI;
case X86::ST0: case X86::ST1: case X86::ST2: case X86::ST3:
case X86::ST4: case X86::ST5: case X86::ST6: case X86::ST7:
return RegNo-X86::ST0;
default:
assert(MRegisterInfo::isVirtualRegister(RegNo) &&
"Unknown physical register!");
assert(0 && "Register allocator hasn't allocated reg correctly yet!");
return 0;
}
}
inline static unsigned char ModRMByte(unsigned Mod, unsigned RegOpcode,
unsigned RM) {
assert(Mod < 4 && RegOpcode < 8 && RM < 8 && "ModRM Fields out of range!");
return RM | (RegOpcode << 3) | (Mod << 6);
}
void Emitter::emitRegModRMByte(unsigned ModRMReg, unsigned RegOpcodeFld){
MCE.emitByte(ModRMByte(3, RegOpcodeFld, getX86RegNum(ModRMReg)));
}
void Emitter::emitSIBByte(unsigned SS, unsigned Index, unsigned Base) {
// SIB byte is in the same format as the ModRMByte...
MCE.emitByte(ModRMByte(SS, Index, Base));
}
void Emitter::emitConstant(unsigned Val, unsigned Size) {
// Output the constant in little endian byte order...
for (unsigned i = 0; i != Size; ++i) {
MCE.emitByte(Val & 255);
Val >>= 8;
}
}
static bool isDisp8(int Value) {
return Value == (signed char)Value;
}
void Emitter::emitMemModRMByte(const MachineInstr &MI,
unsigned Op, unsigned RegOpcodeField) {
const MachineOperand &Op3 = MI.getOperand(Op+3);
GlobalValue *GV = 0;
int DispVal = 0;
if (Op3.isGlobalAddress()) {
GV = Op3.getGlobal();
DispVal = Op3.getOffset();
} else {
DispVal = Op3.getImmedValue();
}
const MachineOperand &Base = MI.getOperand(Op);
const MachineOperand &Scale = MI.getOperand(Op+1);
const MachineOperand &IndexReg = MI.getOperand(Op+2);
unsigned BaseReg = 0;
if (Base.isConstantPoolIndex()) {
// Emit a direct address reference [disp32] where the displacement of the
// constant pool entry is controlled by the MCE.
assert(!GV && "Constant Pool reference cannot be relative to global!");
DispVal += MCE.getConstantPoolEntryAddress(Base.getConstantPoolIndex());
} else {
BaseReg = Base.getReg();
}
// Is a SIB byte needed?
if (IndexReg.getReg() == 0 && BaseReg != X86::ESP) {
if (BaseReg == 0) { // Just a displacement?
// Emit special case [disp32] encoding
MCE.emitByte(ModRMByte(0, RegOpcodeField, 5));
if (GV)
emitGlobalAddressForPtr(GV, DispVal);
else
emitConstant(DispVal, 4);
} else {
unsigned BaseRegNo = getX86RegNum(BaseReg);
if (GV) {
// Emit the most general non-SIB encoding: [REG+disp32]
MCE.emitByte(ModRMByte(2, RegOpcodeField, BaseRegNo));
emitGlobalAddressForPtr(GV, DispVal);
} else if (DispVal == 0 && BaseRegNo != N86::EBP) {
// Emit simple indirect register encoding... [EAX] f.e.
MCE.emitByte(ModRMByte(0, RegOpcodeField, BaseRegNo));
} else if (isDisp8(DispVal)) {
// Emit the disp8 encoding... [REG+disp8]
MCE.emitByte(ModRMByte(1, RegOpcodeField, BaseRegNo));
emitConstant(DispVal, 1);
} else {
// Emit the most general non-SIB encoding: [REG+disp32]
MCE.emitByte(ModRMByte(2, RegOpcodeField, BaseRegNo));
emitConstant(DispVal, 4);
}
}
} else { // We need a SIB byte, so start by outputting the ModR/M byte first
assert(IndexReg.getReg() != X86::ESP && "Cannot use ESP as index reg!");
bool ForceDisp32 = false;
bool ForceDisp8 = false;
if (BaseReg == 0) {
// If there is no base register, we emit the special case SIB byte with
// MOD=0, BASE=5, to JUST get the index, scale, and displacement.
MCE.emitByte(ModRMByte(0, RegOpcodeField, 4));
ForceDisp32 = true;
} else if (GV) {
// Emit the normal disp32 encoding...
MCE.emitByte(ModRMByte(2, RegOpcodeField, 4));
ForceDisp32 = true;
} else if (DispVal == 0 && BaseReg != X86::EBP) {
// Emit no displacement ModR/M byte
MCE.emitByte(ModRMByte(0, RegOpcodeField, 4));
} else if (isDisp8(DispVal)) {
// Emit the disp8 encoding...
MCE.emitByte(ModRMByte(1, RegOpcodeField, 4));
ForceDisp8 = true; // Make sure to force 8 bit disp if Base=EBP
} else {
// Emit the normal disp32 encoding...
MCE.emitByte(ModRMByte(2, RegOpcodeField, 4));
}
// Calculate what the SS field value should be...
static const unsigned SSTable[] = { ~0, 0, 1, ~0, 2, ~0, ~0, ~0, 3 };
unsigned SS = SSTable[Scale.getImmedValue()];
if (BaseReg == 0) {
// Handle the SIB byte for the case where there is no base. The
// displacement has already been output.
assert(IndexReg.getReg() && "Index register must be specified!");
emitSIBByte(SS, getX86RegNum(IndexReg.getReg()), 5);
} else {
unsigned BaseRegNo = getX86RegNum(BaseReg);
unsigned IndexRegNo;
if (IndexReg.getReg())
IndexRegNo = getX86RegNum(IndexReg.getReg());
else
IndexRegNo = 4; // For example [ESP+1*<noreg>+4]
emitSIBByte(SS, IndexRegNo, BaseRegNo);
}
// Do we need to output a displacement?
if (DispVal != 0 || ForceDisp32 || ForceDisp8) {
if (!ForceDisp32 && isDisp8(DispVal))
emitConstant(DispVal, 1);
else if (GV)
emitGlobalAddressForPtr(GV, DispVal);
else
emitConstant(DispVal, 4);
}
}
}
static unsigned sizeOfImm(const TargetInstrDescriptor &Desc) {
switch (Desc.TSFlags & X86II::ImmMask) {
case X86II::Imm8: return 1;
case X86II::Imm16: return 2;
case X86II::Imm32: return 4;
default: assert(0 && "Immediate size not set!");
return 0;
}
}
void Emitter::emitInstruction(const MachineInstr &MI) {
NumEmitted++; // Keep track of the # of mi's emitted
unsigned Opcode = MI.getOpcode();
const TargetInstrDescriptor &Desc = II->get(Opcode);
// Emit the repeat opcode prefix as needed.
if ((Desc.TSFlags & X86II::Op0Mask) == X86II::REP) MCE.emitByte(0xF3);
// Emit instruction prefixes if necessary
if (Desc.TSFlags & X86II::OpSize) MCE.emitByte(0x66);// Operand size...
switch (Desc.TSFlags & X86II::Op0Mask) {
case X86II::TB:
MCE.emitByte(0x0F); // Two-byte opcode prefix
break;
case X86II::REP: break; // already handled.
case X86II::D8: case X86II::D9: case X86II::DA: case X86II::DB:
case X86II::DC: case X86II::DD: case X86II::DE: case X86II::DF:
MCE.emitByte(0xD8+
(((Desc.TSFlags & X86II::Op0Mask)-X86II::D8)
>> X86II::Op0Shift));
break; // Two-byte opcode prefix
default: assert(0 && "Invalid prefix!");
case 0: break; // No prefix!
}
unsigned char BaseOpcode = II->getBaseOpcodeFor(Opcode);
switch (Desc.TSFlags & X86II::FormMask) {
default: assert(0 && "Unknown FormMask value in X86 MachineCodeEmitter!");
case X86II::Pseudo:
if (Opcode != X86::IMPLICIT_USE &&
Opcode != X86::IMPLICIT_DEF &&
Opcode != X86::FP_REG_KILL)
std::cerr << "X86 Machine Code Emitter: No 'form', not emitting: " << MI;
break;
case X86II::RawFrm:
MCE.emitByte(BaseOpcode);
if (MI.getNumOperands() == 1) {
const MachineOperand &MO = MI.getOperand(0);
if (MO.isMachineBasicBlock()) {
emitPCRelativeBlockAddress(MO.getMachineBasicBlock());
} else if (MO.isGlobalAddress()) {
assert(MO.isPCRelative() && "Call target is not PC Relative?");
emitGlobalAddressForCall(MO.getGlobal());
} else if (MO.isExternalSymbol()) {
emitExternalSymbolAddress(MO.getSymbolName(), true);
} else if (MO.isImmediate()) {
emitConstant(MO.getImmedValue(), sizeOfImm(Desc));
} else {
assert(0 && "Unknown RawFrm operand!");
}
}
break;
case X86II::AddRegFrm:
MCE.emitByte(BaseOpcode + getX86RegNum(MI.getOperand(0).getReg()));
if (MI.getNumOperands() == 2) {
const MachineOperand &MO1 = MI.getOperand(1);
if (Value *V = MO1.getVRegValueOrNull()) {
assert(sizeOfImm(Desc) == 4 &&
"Don't know how to emit non-pointer values!");
emitGlobalAddressForPtr(cast<GlobalValue>(V));
} else if (MO1.isGlobalAddress()) {
assert(sizeOfImm(Desc) == 4 &&
"Don't know how to emit non-pointer values!");
assert(!MO1.isPCRelative() && "Function pointer ref is PC relative?");
emitGlobalAddressForPtr(MO1.getGlobal(), MO1.getOffset());
} else if (MO1.isExternalSymbol()) {
assert(sizeOfImm(Desc) == 4 &&
"Don't know how to emit non-pointer values!");
emitExternalSymbolAddress(MO1.getSymbolName(), false);
} else {
emitConstant(MO1.getImmedValue(), sizeOfImm(Desc));
}
}
break;
case X86II::MRMDestReg: {
MCE.emitByte(BaseOpcode);
emitRegModRMByte(MI.getOperand(0).getReg(),
getX86RegNum(MI.getOperand(1).getReg()));
if (MI.getNumOperands() == 3)
emitConstant(MI.getOperand(2).getImmedValue(), sizeOfImm(Desc));
break;
}
case X86II::MRMDestMem:
MCE.emitByte(BaseOpcode);
emitMemModRMByte(MI, 0, getX86RegNum(MI.getOperand(4).getReg()));
if (MI.getNumOperands() == 6)
emitConstant(MI.getOperand(5).getImmedValue(), sizeOfImm(Desc));
break;
case X86II::MRMSrcReg:
MCE.emitByte(BaseOpcode);
emitRegModRMByte(MI.getOperand(1).getReg(),
getX86RegNum(MI.getOperand(0).getReg()));
if (MI.getNumOperands() == 3)
emitConstant(MI.getOperand(2).getImmedValue(), sizeOfImm(Desc));
break;
case X86II::MRMSrcMem:
MCE.emitByte(BaseOpcode);
emitMemModRMByte(MI, 1, getX86RegNum(MI.getOperand(0).getReg()));
if (MI.getNumOperands() == 2+4)
emitConstant(MI.getOperand(5).getImmedValue(), sizeOfImm(Desc));
break;
case X86II::MRM0r: case X86II::MRM1r:
case X86II::MRM2r: case X86II::MRM3r:
case X86II::MRM4r: case X86II::MRM5r:
case X86II::MRM6r: case X86II::MRM7r:
MCE.emitByte(BaseOpcode);
emitRegModRMByte(MI.getOperand(0).getReg(),
(Desc.TSFlags & X86II::FormMask)-X86II::MRM0r);
if (MI.getOperand(MI.getNumOperands()-1).isImmediate()) {
emitConstant(MI.getOperand(MI.getNumOperands()-1).getImmedValue(),
sizeOfImm(Desc));
}
break;
case X86II::MRM0m: case X86II::MRM1m:
case X86II::MRM2m: case X86II::MRM3m:
case X86II::MRM4m: case X86II::MRM5m:
case X86II::MRM6m: case X86II::MRM7m:
MCE.emitByte(BaseOpcode);
emitMemModRMByte(MI, 0, (Desc.TSFlags & X86II::FormMask)-X86II::MRM0m);
if (MI.getNumOperands() == 5) {
if (MI.getOperand(4).isImmediate())
emitConstant(MI.getOperand(4).getImmedValue(), sizeOfImm(Desc));
else if (MI.getOperand(4).isGlobalAddress())
emitGlobalAddressForPtr(MI.getOperand(4).getGlobal(),
MI.getOperand(4).getOffset());
else
assert(0 && "Unknown operand!");
}
break;
}
}
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