MC: First cut at MCFixup, for getting fixup/relocation information out of an MCCodeEmitter.

llvm-svn: 95708
This commit is contained in:
Daniel Dunbar 2010-02-09 22:59:55 +00:00
parent bf02536262
commit b311a6b3ae
6 changed files with 180 additions and 7 deletions

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@ -10,23 +10,60 @@
#ifndef LLVM_MC_MCCODEEMITTER_H
#define LLVM_MC_MCCODEEMITTER_H
#include "llvm/MC/MCFixup.h"
#include <cassert>
namespace llvm {
class MCExpr;
class MCInst;
class raw_ostream;
template<typename T> class SmallVectorImpl;
/// MCFixupKindInfo - Target independent information on a fixup kind.
struct MCFixupKindInfo {
/// A target specific name for the fixup kind. The names will be unique for
/// distinct kinds on any given target.
const char *Name;
/// The bit offset to write the relocation into.
//
// FIXME: These two fields are under-specified and not general enough, but it
// is covers many things, and is enough to let the AsmStreamer pretty-print
// the encoding.
unsigned TargetOffset;
/// The number of bits written by this fixup. The bits are assumed to be
/// contiguous.
unsigned TargetSize;
};
/// MCCodeEmitter - Generic instruction encoding interface.
class MCCodeEmitter {
private:
MCCodeEmitter(const MCCodeEmitter &); // DO NOT IMPLEMENT
void operator=(const MCCodeEmitter &); // DO NOT IMPLEMENT
protected: // Can only create subclasses.
MCCodeEmitter();
public:
virtual ~MCCodeEmitter();
/// @name Target Independent Fixup Information
/// @{
/// getNumFixupKinds - Get the number of target specific fixup kinds.
virtual unsigned getNumFixupKinds() const = 0;
/// getFixupKindInfo - Get information on a fixup kind.
virtual MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const = 0;
/// @}
/// EncodeInstruction - Encode the given \arg Inst to bytes on the output
/// stream \arg OS.
virtual void EncodeInstruction(const MCInst &Inst, raw_ostream &OS) const = 0;
virtual void EncodeInstruction(const MCInst &Inst, raw_ostream &OS,
SmallVectorImpl<MCFixup> &Fixups) const = 0;
};
} // End llvm namespace

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@ -0,0 +1,95 @@
//===-- llvm/MC/MCFixup.h - Instruction Relocation and Patching -*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_MC_MCFIXUP_H
#define LLVM_MC_MCFIXUP_H
#include <cassert>
namespace llvm {
// Private constants, do not use.
//
// This is currently layed out so that the MCFixup fields can be efficiently
// accessed, while keeping the offset field large enought that the assembler
// backend can reasonably use the MCFixup representation for an entire fragment
// (splitting any overly large fragments).
//
// The division of bits between the kind and the opindex can be tweaked if we
// end up needing more bits for target dependent kinds.
enum {
MCFIXUP_NUM_GENERIC_KINDS = 128,
MCFIXUP_NUM_KIND_BITS = 8,
MCFIXUP_NUM_OPINDEX_BITS = 8,
MCFIXUP_NUM_OFFSET_BITS = (32 - MCFIXUP_NUM_OPINDEX_BITS -
MCFIXUP_NUM_OPINDEX_BITS)
};
/// MCFixupKind - Extensible enumeration to represent the type of a fixup.
enum MCFixupKind {
FK_Data_1 = 0, ///< A one-byte fixup.
FK_Data_2, ///< A two-byte fixup.
FK_Data_4, ///< A four-byte fixup.
FK_Data_8, ///< A eight-byte fixup.
FirstTargetFixupKind = MCFIXUP_NUM_GENERIC_KINDS,
MaxTargetFixupKind = (1 << MCFIXUP_NUM_KIND_BITS)
};
/// MCFixup - Encode information on a single operation to perform on an byte
/// sequence (e.g., an encoded instruction) which requires assemble- or run-
/// time patching.
///
/// Fixups are used any time the target instruction encoder needs to represent
/// some value in an instruction which is not yet concrete. The encoder will
/// encode the instruction assuming the value is 0, and emit a fixup which
/// communicates to the assembler backend how it should rewrite the encoded
/// value.
///
/// During the process of relaxation, the assembler will apply fixups as
/// symbolic values become concrete. When relaxation is complete, any remaining
/// fixups become relocations in the object file (or errors, if the fixup cannot
/// be encoded on the target).
class MCFixup {
static const unsigned MaxOffset = 1 << MCFIXUP_NUM_KIND_BITS;
/// The byte index of start of the relocation inside the encoded instruction.
unsigned Offset : MCFIXUP_NUM_OFFSET_BITS;
/// The index of the operand to encode into the instruction.
unsigned OpIndex : MCFIXUP_NUM_OPINDEX_BITS;
/// The target dependent kind of fixup item this is. The kind is used to
/// determine how the operand value should be encoded into the instruction.
unsigned Kind : MCFIXUP_NUM_KIND_BITS;
public:
static MCFixup Create(unsigned Offset, unsigned OpIndex, MCFixupKind Kind) {
MCFixup FI;
FI.Offset = Offset;
FI.OpIndex = OpIndex;
FI.Kind = unsigned(Kind);
assert(Offset == FI.Offset && "Offset out of range!");
assert(OpIndex == FI.OpIndex && "Operand index out of range!");
assert(Kind == FI.Kind && "Kind out of range!");
return FI;
}
unsigned getOffset() const { return Offset; }
unsigned getOpIndex() const { return OpIndex; }
MCFixupKind getKind() const { return MCFixupKind(Kind); }
};
} // End llvm namespace
#endif

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@ -535,8 +535,9 @@ void MCAsmStreamer::EmitInstruction(const MCInst &Inst) {
// Show the encoding in a comment if we have a code emitter.
if (Emitter) {
SmallString<256> Code;
SmallVector<MCFixup, 4> Fixups;
raw_svector_ostream VecOS(Code);
Emitter->EncodeInstruction(Inst, VecOS);
Emitter->EncodeInstruction(Inst, VecOS, Fixups);
VecOS.flush();
raw_ostream &OS = GetCommentOS();

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@ -366,9 +366,10 @@ void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
CurSectionData->setHasInstructions(true);
// FIXME: Relocations!
SmallVector<MCFixup, 4> Fixups;
SmallString<256> Code;
raw_svector_ostream VecOS(Code);
Emitter->EncodeInstruction(Inst, VecOS);
Emitter->EncodeInstruction(Inst, VecOS, Fixups);
EmitBytes(VecOS.str(), 0);
}

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@ -944,6 +944,24 @@ public:
delete DummyF;
}
unsigned getNumFixupKinds() const {
return 5;
}
MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const {
static MCFixupKindInfo Infos[] = {
{ "reloc_pcrel_word", 0, 4 * 8 },
{ "reloc_picrel_word", 0, 4 * 8 },
{ "reloc_absolute_word", 0, 4 * 8 },
{ "reloc_absolute_word_sext", 0, 4 * 8 },
{ "reloc_absolute_dword", 0, 8 * 8 }
};
assert(Kind >= FirstTargetFixupKind && Kind < MaxTargetFixupKind &&
"Invalid kind!");
return Infos[Kind - FirstTargetFixupKind];
}
bool AddRegToInstr(const MCInst &MI, MachineInstr *Instr,
unsigned Start) const {
if (Start + 1 > MI.getNumOperands())
@ -997,7 +1015,8 @@ public:
AddRegToInstr(MI, Instr, Start + 4));
}
void EncodeInstruction(const MCInst &MI, raw_ostream &OS) const {
void EncodeInstruction(const MCInst &MI, raw_ostream &OS,
SmallVectorImpl<MCFixup> &Fixups) const {
// Don't look yet!
// Convert the MCInst to a MachineInstr so we can (ab)use the regular

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@ -33,6 +33,24 @@ public:
}
~X86MCCodeEmitter() {}
unsigned getNumFixupKinds() const {
return 5;
}
MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const {
static MCFixupKindInfo Infos[] = {
{ "reloc_pcrel_word", 0, 4 * 8 },
{ "reloc_picrel_word", 0, 4 * 8 },
{ "reloc_absolute_word", 0, 4 * 8 },
{ "reloc_absolute_word_sext", 0, 4 * 8 },
{ "reloc_absolute_dword", 0, 8 * 8 }
};
assert(Kind >= FirstTargetFixupKind && Kind < MaxTargetFixupKind &&
"Invalid kind!");
return Infos[Kind - FirstTargetFixupKind];
}
static unsigned GetX86RegNum(const MCOperand &MO) {
return X86RegisterInfo::getX86RegNum(MO.getReg());
@ -75,7 +93,8 @@ public:
unsigned RegOpcodeField, intptr_t PCAdj,
raw_ostream &OS) const;
void EncodeInstruction(const MCInst &MI, raw_ostream &OS) const;
void EncodeInstruction(const MCInst &MI, raw_ostream &OS,
SmallVectorImpl<MCFixup> &Fixups) const;
};
@ -379,7 +398,8 @@ static unsigned DetermineREXPrefix(const MCInst &MI, unsigned TSFlags,
}
void X86MCCodeEmitter::
EncodeInstruction(const MCInst &MI, raw_ostream &OS) const {
EncodeInstruction(const MCInst &MI, raw_ostream &OS,
SmallVectorImpl<MCFixup> &Fixups) const {
unsigned Opcode = MI.getOpcode();
const TargetInstrDesc &Desc = TII.get(Opcode);
unsigned TSFlags = Desc.TSFlags;