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MC: When running with -mc-relax-all, we can eagerly relax instructions and avoid creating unnecessary MCInstFragments. 

llvm-svn: 104736
This commit is contained in:
Daniel Dunbar 2010-05-26 20:37:03 +00:00
parent 9d40ef162b
commit b889fc987e
2 changed files with 20 additions and 21 deletions
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7
llvm/lib/MC/MCAssembler.cpp
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@ -845,11 +845,8 @@ bool MCAssembler::LayoutOnce(MCAsmLayout &Layout) {
for (unsigned i = 0, e = Fixups.size(); i != e; ++i) for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
IF->getFixups().push_back(Fixups[i]); IF->getFixups().push_back(Fixups[i]);
// Update the layout, and remember that we relaxed. If we are relaxing // Update the layout, and remember that we relaxed.
// everything, we can skip this step since nothing will depend on updating Layout.UpdateForSlide(IF, SlideAmount);
// the values.
if (!getRelaxAll())
Layout.UpdateForSlide(IF, SlideAmount);
WasRelaxed = true; WasRelaxed = true;
} }
} }

34
llvm/lib/MC/MCMachOStreamer.cpp
View File

@ -463,23 +463,25 @@ void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
CurSectionData->setHasInstructions(true); CurSectionData->setHasInstructions(true);
// See if we might need to relax this instruction, if so it needs its own // If this instruction doesn't need relaxation, just emit it as data.
// fragment. if (!Assembler.getBackend().MayNeedRelaxation(Inst)) {
//
// 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 (Assembler.getBackend().MayNeedRelaxation(Inst))
EmitInstToFragment(Inst);
else
EmitInstToData(Inst); EmitInstToData(Inst);
return;
}
// Otherwise, if we are relaxing everything, relax the instruction as much as
// possible and emit it as data.
if (Assembler.getRelaxAll()) {
MCInst Relaxed;
Assembler.getBackend().RelaxInstruction(Inst, Relaxed);
while (Assembler.getBackend().MayNeedRelaxation(Relaxed))
Assembler.getBackend().RelaxInstruction(Relaxed, Relaxed);
EmitInstToData(Relaxed);
return;
}
// Otherwise emit to a separate fragment.
EmitInstToFragment(Inst);
} }
void MCMachOStreamer::Finish() { void MCMachOStreamer::Finish() {