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b90ed644fc
llvm-6502/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
Matheus Almeida b90ed644fc [mips] Add checks for alignment and maximum displacements for most of the 
branch instructions for mips and micromips instruction sets thus avoiding
the situation of generating branches to undesired locations if offsets
cannot be encoded.

This patch also checks if a fixup cannot be applied and returns a fatal error
if that's the case.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197223 91177308-0d34-0410-b5e6-96231b3b80d8
2013-12-13 11:11:02 +00:00

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//===-- MipsASMBackend.cpp - Mips Asm Backend ----------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the MipsAsmBackend and MipsELFObjectWriter classes.
//
//===----------------------------------------------------------------------===//
//
#include "MipsFixupKinds.h"
#include "MCTargetDesc/MipsMCTargetDesc.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDirectives.h"
#include "llvm/MC/MCELFObjectWriter.h"
#include "llvm/MC/MCFixupKindInfo.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/MathExtras.h"
using namespace llvm;
// Prepare value for the target space for it
static unsigned adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
MCContext *Ctx = NULL) {
unsigned Kind = Fixup.getKind();
// Add/subtract and shift
switch (Kind) {
default:
return 0;
case FK_GPRel_4:
case FK_Data_4:
case FK_Data_8:
case Mips::fixup_Mips_LO16:
case Mips::fixup_Mips_GPREL16:
case Mips::fixup_Mips_GPOFF_HI:
case Mips::fixup_Mips_GPOFF_LO:
case Mips::fixup_Mips_GOT_PAGE:
case Mips::fixup_Mips_GOT_OFST:
case Mips::fixup_Mips_GOT_DISP:
case Mips::fixup_Mips_GOT_LO16:
case Mips::fixup_Mips_CALL_LO16:
case Mips::fixup_MICROMIPS_LO16:
case Mips::fixup_MICROMIPS_GOT_PAGE:
case Mips::fixup_MICROMIPS_GOT_OFST:
case Mips::fixup_MICROMIPS_GOT_DISP:
break;
case Mips::fixup_Mips_PC16:
// So far we are only using this type for branches.
// For branches we start 1 instruction after the branch
// so the displacement will be one instruction size less.
Value -= 4;
// The displacement is then divided by 4 to give us an 18 bit
// address range. Forcing a signed division because Value can be negative.
Value = (int64_t)Value / 4;
// We now check if Value can be encoded as a 16-bit signed immediate.
if (!isIntN(15, Value) && Ctx)
Ctx->FatalError(Fixup.getLoc(), "out of range PC16 fixup");
break;
case Mips::fixup_Mips_26:
// So far we are only using this type for jumps.
// The displacement is then divided by 4 to give us an 28 bit
// address range.
Value >>= 2;
break;
case Mips::fixup_Mips_HI16:
case Mips::fixup_Mips_GOT_Local:
case Mips::fixup_Mips_GOT_HI16:
case Mips::fixup_Mips_CALL_HI16:
case Mips::fixup_MICROMIPS_HI16:
// Get the 2nd 16-bits. Also add 1 if bit 15 is 1.
Value = ((Value + 0x8000) >> 16) & 0xffff;
break;
case Mips::fixup_Mips_HIGHER:
// Get the 3rd 16-bits.
Value = ((Value + 0x80008000LL) >> 32) & 0xffff;
break;
case Mips::fixup_Mips_HIGHEST:
// Get the 4th 16-bits.
Value = ((Value + 0x800080008000LL) >> 48) & 0xffff;
break;
case Mips::fixup_MICROMIPS_26_S1:
Value >>= 1;
break;
case Mips::fixup_MICROMIPS_PC16_S1:
Value -= 4;
// Forcing a signed division because Value can be negative.
Value = (int64_t)Value / 2;
// We now check if Value can be encoded as a 16-bit signed immediate.
if (!isIntN(15, Value) && Ctx)
Ctx->FatalError(Fixup.getLoc(), "out of range PC16 fixup");
break;
}
return Value;
}
namespace {
class MipsAsmBackend : public MCAsmBackend {
Triple::OSType OSType;
bool IsLittle; // Big or little endian
bool Is64Bit; // 32 or 64 bit words
public:
MipsAsmBackend(const Target &T, Triple::OSType _OSType,
bool _isLittle, bool _is64Bit)
:MCAsmBackend(), OSType(_OSType), IsLittle(_isLittle), Is64Bit(_is64Bit) {}
MCObjectWriter *createObjectWriter(raw_ostream &OS) const {
return createMipsELFObjectWriter(OS,
MCELFObjectTargetWriter::getOSABI(OSType), IsLittle, Is64Bit);
}
/// ApplyFixup - Apply the \p Value for given \p Fixup into the provided
/// data fragment, at the offset specified by the fixup and following the
/// fixup kind as appropriate.
void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
uint64_t Value) const {
MCFixupKind Kind = Fixup.getKind();
Value = adjustFixupValue(Fixup, Value);
if (!Value)
return; // Doesn't change encoding.
// Where do we start in the object
unsigned Offset = Fixup.getOffset();
// Number of bytes we need to fixup
unsigned NumBytes = (getFixupKindInfo(Kind).TargetSize + 7) / 8;
// Used to point to big endian bytes
unsigned FullSize;
switch ((unsigned)Kind) {
case Mips::fixup_Mips_16:
FullSize = 2;
break;
case Mips::fixup_Mips_64:
FullSize = 8;
break;
default:
FullSize = 4;
break;
}
// Grab current value, if any, from bits.
uint64_t CurVal = 0;
for (unsigned i = 0; i != NumBytes; ++i) {
unsigned Idx = IsLittle ? i : (FullSize - 1 - i);
CurVal |= (uint64_t)((uint8_t)Data[Offset + Idx]) << (i*8);
}
uint64_t Mask = ((uint64_t)(-1) >>
(64 - getFixupKindInfo(Kind).TargetSize));
CurVal |= Value & Mask;
// Write out the fixed up bytes back to the code/data bits.
for (unsigned i = 0; i != NumBytes; ++i) {
unsigned Idx = IsLittle ? i : (FullSize - 1 - i);
Data[Offset + Idx] = (uint8_t)((CurVal >> (i*8)) & 0xff);
}
}
unsigned getNumFixupKinds() const { return Mips::NumTargetFixupKinds; }
const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const {
const static MCFixupKindInfo Infos[Mips::NumTargetFixupKinds] = {
// This table *must* be in same the order of fixup_* kinds in
// MipsFixupKinds.h.
//
// name offset bits flags
{ "fixup_Mips_16", 0, 16, 0 },
{ "fixup_Mips_32", 0, 32, 0 },
{ "fixup_Mips_REL32", 0, 32, 0 },
{ "fixup_Mips_26", 0, 26, 0 },
{ "fixup_Mips_HI16", 0, 16, 0 },
{ "fixup_Mips_LO16", 0, 16, 0 },
{ "fixup_Mips_GPREL16", 0, 16, 0 },
{ "fixup_Mips_LITERAL", 0, 16, 0 },
{ "fixup_Mips_GOT_Global", 0, 16, 0 },
{ "fixup_Mips_GOT_Local", 0, 16, 0 },
{ "fixup_Mips_PC16", 0, 16, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_Mips_CALL16", 0, 16, 0 },
{ "fixup_Mips_GPREL32", 0, 32, 0 },
{ "fixup_Mips_SHIFT5", 6, 5, 0 },
{ "fixup_Mips_SHIFT6", 6, 5, 0 },
{ "fixup_Mips_64", 0, 64, 0 },
{ "fixup_Mips_TLSGD", 0, 16, 0 },
{ "fixup_Mips_GOTTPREL", 0, 16, 0 },
{ "fixup_Mips_TPREL_HI", 0, 16, 0 },
{ "fixup_Mips_TPREL_LO", 0, 16, 0 },
{ "fixup_Mips_TLSLDM", 0, 16, 0 },
{ "fixup_Mips_DTPREL_HI", 0, 16, 0 },
{ "fixup_Mips_DTPREL_LO", 0, 16, 0 },
{ "fixup_Mips_Branch_PCRel", 0, 16, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_Mips_GPOFF_HI", 0, 16, 0 },
{ "fixup_Mips_GPOFF_LO", 0, 16, 0 },
{ "fixup_Mips_GOT_PAGE", 0, 16, 0 },
{ "fixup_Mips_GOT_OFST", 0, 16, 0 },
{ "fixup_Mips_GOT_DISP", 0, 16, 0 },
{ "fixup_Mips_HIGHER", 0, 16, 0 },
{ "fixup_Mips_HIGHEST", 0, 16, 0 },
{ "fixup_Mips_GOT_HI16", 0, 16, 0 },
{ "fixup_Mips_GOT_LO16", 0, 16, 0 },
{ "fixup_Mips_CALL_HI16", 0, 16, 0 },
{ "fixup_Mips_CALL_LO16", 0, 16, 0 },
{ "fixup_MICROMIPS_26_S1", 0, 26, 0 },
{ "fixup_MICROMIPS_HI16", 0, 16, 0 },
{ "fixup_MICROMIPS_LO16", 0, 16, 0 },
{ "fixup_MICROMIPS_GOT16", 0, 16, 0 },
{ "fixup_MICROMIPS_PC16_S1", 0, 16, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_MICROMIPS_CALL16", 0, 16, 0 },
{ "fixup_MICROMIPS_GOT_DISP", 0, 16, 0 },
{ "fixup_MICROMIPS_GOT_PAGE", 0, 16, 0 },
{ "fixup_MICROMIPS_GOT_OFST", 0, 16, 0 },
{ "fixup_MICROMIPS_TLS_DTPREL_HI16", 0, 16, 0 },
{ "fixup_MICROMIPS_TLS_DTPREL_LO16", 0, 16, 0 },
{ "fixup_MICROMIPS_TLS_TPREL_HI16", 0, 16, 0 },
{ "fixup_MICROMIPS_TLS_TPREL_LO16", 0, 16, 0 }
};
if (Kind < FirstTargetFixupKind)
return MCAsmBackend::getFixupKindInfo(Kind);
assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
"Invalid kind!");
return Infos[Kind - FirstTargetFixupKind];
}
/// @name Target Relaxation Interfaces
/// @{
/// MayNeedRelaxation - Check whether the given instruction may need
/// relaxation.
///
/// \param Inst - The instruction to test.
bool mayNeedRelaxation(const MCInst &Inst) const {
return false;
}
/// fixupNeedsRelaxation - Target specific predicate for whether a given
/// fixup requires the associated instruction to be relaxed.
bool fixupNeedsRelaxation(const MCFixup &Fixup,
uint64_t Value,
const MCRelaxableFragment *DF,
const MCAsmLayout &Layout) const {
// FIXME.
assert(0 && "RelaxInstruction() unimplemented");
return false;
}
/// RelaxInstruction - Relax the instruction in the given fragment
/// to the next wider instruction.
///
/// \param Inst - The instruction to relax, which may be the same
/// as the output.
/// \param [out] Res On return, the relaxed instruction.
void relaxInstruction(const MCInst &Inst, MCInst &Res) const {
}
/// @}
/// WriteNopData - Write an (optimal) nop sequence of Count bytes
/// to the given output. If the target cannot generate such a sequence,
/// it should return an error.
///
/// \return - True on success.
bool writeNopData(uint64_t Count, MCObjectWriter *OW) const {
// Check for a less than instruction size number of bytes
// FIXME: 16 bit instructions are not handled yet here.
// We shouldn't be using a hard coded number for instruction size.
if (Count % 4) return false;
uint64_t NumNops = Count / 4;
for (uint64_t i = 0; i != NumNops; ++i)
OW->Write32(0);
return true;
}
/// processFixupValue - Target hook to process the literal value of a fixup
/// if necessary.
void processFixupValue(const MCAssembler &Asm, const MCAsmLayout &Layout,
const MCFixup &Fixup, const MCFragment *DF,
MCValue &Target, uint64_t &Value,
bool &IsResolved) {
// At this point we'll ignore the value returned by adjustFixupValue as
// we are only checking if the fixup can be applied correctly. We have
// access to MCContext from here which allows us to report a fatal error
// with *possibly* a source code location.
(void)adjustFixupValue(Fixup, Value, &Asm.getContext());
}
}; // class MipsAsmBackend
} // namespace
// MCAsmBackend
MCAsmBackend *llvm::createMipsAsmBackendEL32(const Target &T,
const MCRegisterInfo &MRI,
StringRef TT,
StringRef CPU) {
return new MipsAsmBackend(T, Triple(TT).getOS(),
/*IsLittle*/true, /*Is64Bit*/false);
}
MCAsmBackend *llvm::createMipsAsmBackendEB32(const Target &T,
const MCRegisterInfo &MRI,
StringRef TT,
StringRef CPU) {
return new MipsAsmBackend(T, Triple(TT).getOS(),
/*IsLittle*/false, /*Is64Bit*/false);
}
MCAsmBackend *llvm::createMipsAsmBackendEL64(const Target &T,
const MCRegisterInfo &MRI,
StringRef TT,
StringRef CPU) {
return new MipsAsmBackend(T, Triple(TT).getOS(),
/*IsLittle*/true, /*Is64Bit*/true);
}
MCAsmBackend *llvm::createMipsAsmBackendEB64(const Target &T,
const MCRegisterInfo &MRI,
StringRef TT,
StringRef CPU) {
return new MipsAsmBackend(T, Triple(TT).getOS(),
/*IsLittle*/false, /*Is64Bit*/true);
}
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