[llvm-commits] [llvm] r112260 - /llvm/trunk/lib/MC/MCELFStreamer.cpp

[Benjamin Kramer]

Author: d0k
Date: Fri Aug 27 05:40:51 2010
New Revision: 112260

URL: http://llvm.org/viewvc/llvm-project?rev=112260&view=rev
Log:
MCELF: Port EmitInstruction changes from MachO streamer. Patch by Roman Divacky.

Modified:
    llvm/trunk/lib/MC/MCELFStreamer.cpp

Modified: llvm/trunk/lib/MC/MCELFStreamer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCELFStreamer.cpp?rev=112260&r1=112259&r2=112260&view=diff
==============================================================================
--- llvm/trunk/lib/MC/MCELFStreamer.cpp (original)
+++ llvm/trunk/lib/MC/MCELFStreamer.cpp Fri Aug 27 05:40:51 2010
@@ -34,6 +34,8 @@
 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)
@@ -328,16 +330,25 @@
   SD.setFlags(ELF_STT_File | ELF_STB_Local | ELF_STV_Default);
 }
 
-void MCELFStreamer::EmitInstruction(const MCInst &Inst) {
-  // Scan for values.
-  for (unsigned i = 0; i != Inst.getNumOperands(); ++i)
-    if (Inst.getOperand(i).isExpr())
-      AddValueSymbols(Inst.getOperand(i).getExpr());
+void MCELFStreamer::EmitInstToFragment(const MCInst &Inst) {
+  MCInstFragment *IF = new MCInstFragment(Inst, getCurrentSectionData());
 
-  getCurrentSectionData()->setHasInstructions(true);
+  // 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();
 
-  // FIXME-PERF: Common case is that we don't need to relax, encode directly
-  // onto the data fragments buffers.
+  IF->getCode() = Code;
+  IF->getFixups() = Fixups;
+}
+
+void MCELFStreamer::EmitInstToData(const MCInst &Inst) {
+  MCDataFragment *DF = getOrCreateDataFragment();
 
   SmallVector<MCFixup, 4> Fixups;
   SmallString<256> Code;
@@ -345,47 +356,41 @@
   getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
   VecOS.flush();
 
-  // FIXME: Eliminate this copy.
-  SmallVector<MCFixup, 4> AsmFixups;
+  // Add the fixups and data.
   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()));
+    Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
+    DF->addFixup(Fixups[i]);
   }
+  DF->getContents().append(Code.begin(), Code.end());
+}
 
-  // 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;
+void MCELFStreamer::EmitInstruction(const MCInst &Inst) {
+  // Scan for values.
+  for (unsigned i = 0; i != Inst.getNumOperands(); ++i)
+    if (Inst.getOperand(i).isExpr())
+      AddValueSymbols(Inst.getOperand(i).getExpr());
+
+  getCurrentSectionData()->setHasInstructions(true);
 
+  // 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() {