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MCELF: Port EmitInstruction changes from MachO streamer. Patch by Roman Divacky.

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llvm-svn: 112260
This commit is contained in:
Benjamin Kramer 2010-08-27 10:40:51 +00:00
parent 4e04c2e69f
commit f5c811611e
1 changed files with 51 additions and 46 deletions
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97
lib/MC/MCELFStreamer.cpp
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@ -34,6 +34,8 @@ using namespace llvm;
namespace {
class MCELFStreamer : public MCObjectStreamer {
void EmitInstToFragment(const MCInst &Inst);
void EmitInstToData(const MCInst &Inst);
public:
MCELFStreamer(MCContext &Context, TargetAsmBackend &TAB,
raw_ostream &OS, MCCodeEmitter *Emitter)
@ -328,6 +330,40 @@ void MCELFStreamer::EmitFileDirective(StringRef Filename) {
SD.setFlags(ELF_STT_File | ELF_STB_Local | ELF_STV_Default);
}
void MCELFStreamer::EmitInstToFragment(const MCInst &Inst) {
MCInstFragment *IF = new MCInstFragment(Inst, getCurrentSectionData());
// Add the fixups and data.
//
// FIXME: Revisit this design decision when relaxation is done, we may be
// able to get away with not storing any extra data in the MCInst.
SmallVector<MCFixup, 4> Fixups;
SmallString<256> Code;
raw_svector_ostream VecOS(Code);
getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
VecOS.flush();
IF->getCode() = Code;
IF->getFixups() = Fixups;
}
void MCELFStreamer::EmitInstToData(const MCInst &Inst) {
MCDataFragment *DF = getOrCreateDataFragment();
SmallVector<MCFixup, 4> Fixups;
SmallString<256> Code;
raw_svector_ostream VecOS(Code);
getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
VecOS.flush();
// Add the fixups and data.
for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
DF->addFixup(Fixups[i]);
}
DF->getContents().append(Code.begin(), Code.end());
}
void MCELFStreamer::EmitInstruction(const MCInst &Inst) {
// Scan for values.
for (unsigned i = 0; i != Inst.getNumOperands(); ++i)
@ -336,56 +372,25 @@ void MCELFStreamer::EmitInstruction(const MCInst &Inst) {
getCurrentSectionData()->setHasInstructions(true);
// FIXME-PERF: Common case is that we don't need to relax, encode directly
// onto the data fragments buffers.
SmallVector<MCFixup, 4> Fixups;
SmallString<256> Code;
raw_svector_ostream VecOS(Code);
getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
VecOS.flush();
// FIXME: Eliminate this copy.
SmallVector<MCFixup, 4> AsmFixups;
for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
MCFixup &F = Fixups[i];
AsmFixups.push_back(MCFixup::Create(F.getOffset(), F.getValue(),
F.getKind()));
}
// See if we might need to relax this instruction, if so it needs its own
// fragment.
//
// FIXME-PERF: Support target hook to do a fast path that avoids the encoder,
// when we can immediately tell that we will get something which might need
// relaxation (and compute its size).
//
// FIXME-PERF: We should also be smart about immediately relaxing instructions
// which we can already show will never possibly fit (we can also do a very
// good job of this before we do the first relaxation pass, because we have
// total knowledge about undefined symbols at that point). Even now, though,
// we can do a decent job, especially on Darwin where scattering means that we
// are going to often know that we can never fully resolve a fixup.
if (getAssembler().getBackend().MayNeedRelaxation(Inst)) {
MCInstFragment *IF = new MCInstFragment(Inst, getCurrentSectionData());
// Add the fixups and data.
//
// FIXME: Revisit this design decision when relaxation is done, we may be
// able to get away with not storing any extra data in the MCInst.
IF->getCode() = Code;
IF->getFixups() = AsmFixups;
// If this instruction doesn't need relaxation, just emit it as data.
if (!getAssembler().getBackend().MayNeedRelaxation(Inst)) {
EmitInstToData(Inst);
return;
}
// Add the fixups and data.
MCDataFragment *DF = getOrCreateDataFragment();
for (unsigned i = 0, e = AsmFixups.size(); i != e; ++i) {
AsmFixups[i].setOffset(AsmFixups[i].getOffset() + DF->getContents().size());
DF->addFixup(AsmFixups[i]);
// Otherwise, if we are relaxing everything, relax the instruction as much as
// possible and emit it as data.
if (getAssembler().getRelaxAll()) {
MCInst Relaxed;
getAssembler().getBackend().RelaxInstruction(Inst, Relaxed);
while (getAssembler().getBackend().MayNeedRelaxation(Relaxed))
getAssembler().getBackend().RelaxInstruction(Relaxed, Relaxed);
EmitInstToData(Relaxed);
return;
}
DF->getContents().append(Code.begin(), Code.end());
// Otherwise emit to a separate fragment.
EmitInstToFragment(Inst);
}
void MCELFStreamer::Finish() {