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MC: Add TargetAsmBackend::RelaxInstruction callback, and custom X86 implementation. 

llvm-svn: 99245
This commit is contained in:
Daniel Dunbar 2010-03-23 01:39:09 +00:00
parent 16cbe95dd6
commit e0c43577c1
2 changed files with 57 additions and 0 deletions
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7
llvm/include/llvm/Target/TargetAsmBackend.h
View File

@ -15,6 +15,8 @@
namespace llvm {
class MCAsmFixup;
class MCDataFragment;
class MCInst;
class MCInstFragment;
class MCObjectWriter;
class MCSection;
class Target;
@ -95,6 +97,11 @@ public:
/// fixup kind as appropriate.
virtual void ApplyFixup(const MCAsmFixup &Fixup, MCDataFragment &Fragment,
uint64_t Value) const = 0;
/// RelaxInstruction - Relax the instruction in the given fragment to the next
/// wider instruction.
virtual void RelaxInstruction(const MCInstFragment *IF,
MCInst &Res) const = 0;
};
} // End llvm namespace

50
llvm/lib/Target/X86/X86AsmBackend.cpp
View File

@ -10,10 +10,13 @@
#include "llvm/Target/TargetAsmBackend.h"
#include "X86.h"
#include "X86FixupKinds.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MachObjectWriter.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetRegistry.h"
#include "llvm/Target/TargetAsmBackend.h"
using namespace llvm;
@ -48,8 +51,55 @@ public:
for (unsigned i = 0; i != Size; ++i)
DF.getContents()[Fixup.Offset + i] = uint8_t(Value >> (i * 8));
}
void RelaxInstruction(const MCInstFragment *IF, MCInst &Res) const;
};
static unsigned getRelaxedOpcode(unsigned Op) {
switch (Op) {
default:
return Op;
case X86::JAE_1: return X86::JAE_4;
case X86::JA_1: return X86::JA_4;
case X86::JBE_1: return X86::JBE_4;
case X86::JB_1: return X86::JB_4;
case X86::JE_1: return X86::JE_4;
case X86::JGE_1: return X86::JGE_4;
case X86::JG_1: return X86::JG_4;
case X86::JLE_1: return X86::JLE_4;
case X86::JL_1: return X86::JL_4;
case X86::JMP_1: return X86::JMP_4;
case X86::JNE_1: return X86::JNE_4;
case X86::JNO_1: return X86::JNO_4;
case X86::JNP_1: return X86::JNP_4;
case X86::JNS_1: return X86::JNS_4;
case X86::JO_1: return X86::JO_4;
case X86::JP_1: return X86::JP_4;
case X86::JS_1: return X86::JS_4;
}
}
// FIXME: Can tblgen help at all here to verify there aren't other instructions
// we can relax?
void X86AsmBackend::RelaxInstruction(const MCInstFragment *IF,
MCInst &Res) const {
// The only relaxations X86 does is from a 1byte pcrel to a 4byte pcrel.
unsigned RelaxedOp = getRelaxedOpcode(IF->getInst().getOpcode());
if (RelaxedOp == IF->getInst().getOpcode()) {
SmallString<256> Tmp;
raw_svector_ostream OS(Tmp);
IF->getInst().dump_pretty(OS);
llvm_report_error("unexpected instruction to relax: " + OS.str());
}
Res = IF->getInst();
Res.setOpcode(RelaxedOp);
}
/* *** */
class ELFX86AsmBackend : public X86AsmBackend {
public:
ELFX86AsmBackend(const Target &T)