For Darwin, emit all the text section directives together before the dwarf

section directives.  This causes the assembler to put the text sections at
the beginning of the object file, which helps work around a limitation of the
Darwin ARM relocations.  Radar 7255355.

llvm-svn: 83127

Author: bob-wilson

llvm/lib/Target/ARM/AsmPrinter/ARMAsmPrinter.cpp

@@ -1046,6 +1046,25 @@ void ARMAsmPrinter::printMachineInstruction(const MachineInstr *MI) {
 
 bool ARMAsmPrinter::doInitialization(Module &M) {
 
+  if (Subtarget->isTargetDarwin()) {
+    Reloc::Model RelocM = TM.getRelocationModel();
+    if (RelocM == Reloc::PIC_ || RelocM == Reloc::DynamicNoPIC) {
+      // Declare all the text sections up front (before the DWARF sections
+      // emitted by AsmPrinter::doInitialization) so the assembler will keep
+      // them together at the beginning of the object file.  This helps
+      // avoid out-of-range branches that are due a fundamental limitation of
+      // the way symbol offsets are encoded with the current Darwin ARM
+      // relocations.
+      O << "\t.section __TEXT,__text,regular\n"
+        << "\t.section __TEXT,__textcoal_nt,coalesced\n"
+        << "\t.section __TEXT,__const_coal,coalesced\n";
+      if (RelocM == Reloc::DynamicNoPIC)
+        O << "\t.section __TEXT,__symbol_stub4,symbol_stubs,none,12\n";
+      else
+        O << "\t.section __TEXT,__picsymbolstub4,symbol_stubs,none,16\n";
+    }
+  }
+
   bool Result = AsmPrinter::doInitialization(M);
   DW = getAnalysisIfAvailable<DwarfWriter>();