MC: Add TargetAsmBackend::MayNeedRelaxation, for checking whether a particular instruction + fixups might need relaxation.

llvm-svn: 99249

2 files changed, 12 insertions, 5 deletions

diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index 7672528524b..031820d5286 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -715,7 +715,7 @@ void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
 
       // Create a new data fragment for the instruction.
       //
-      // FIXME: Reuse previous data fragment if possible.
+      // FIXME-PERF: Reuse previous data fragment if possible.
       MCDataFragment *DF = new MCDataFragment();
       SD.getFragmentList().insert(it2, DF);
 
diff --git a/llvm/lib/MC/MCMachOStreamer.cpp b/llvm/lib/MC/MCMachOStreamer.cpp
index a52d962c9a4..2a1aa273014 100644
--- a/llvm/lib/MC/MCMachOStreamer.cpp
+++ b/llvm/lib/MC/MCMachOStreamer.cpp
@@ -383,12 +383,19 @@ void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
   Assembler.getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
   VecOS.flush();
 
-  // Add the fixups and data.
-  MCDataFragment *DF = getOrCreateDataFragment();
+  // FIXME: Eliminate this copy.
+  SmallVector<MCAsmFixup, 4> AsmFixups;
   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
     MCFixup &F = Fixups[i];
-    DF->addFixup(MCAsmFixup(DF->getContents().size()+F.getOffset(),
-                            *F.getValue(), F.getKind()));
+    AsmFixups.push_back(MCAsmFixup(F.getOffset(), *F.getValue(),
+                                   F.getKind()));
+  }
+
+  // Add the fixups and data.
+  MCDataFragment *DF = getOrCreateDataFragment();
+  for (unsigned i = 0, e = AsmFixups.size(); i != e; ++i) {
+    AsmFixups[i].Offset += DF->getContents().size();
+    DF->addFixup(AsmFixups[i]);
   }
   DF->getContents().append(Code.begin(), Code.end());
 }