Emit all D inline asm labels as local labels.

On OS X, there is an actual significance to the distinction, which before lead e.g. to exception throwing in the below example being broken:

---
import core.exception;

void main() {
  asm {
    jmp Lfoo;
Lfoo:
    ;
  }
  throw cast(OutOfMemoryError)cast(void*)OutOfMemoryError.classinfo.init;
  assert(0);
}
---

gen/asm-x86-32.h

@@ -1592,7 +1592,7 @@ namespace AsmParserx8632
 
         void addLabel ( char* id )
         {
-            insnTemplate << sc->func->mangle() <<  "_" << id;
+            printLabelName(insnTemplate, sc->func->mangle(), id);
         }
 
         /* Determines whether the operand is a register, memory reference

gen/asm-x86-64.h

@@ -1725,7 +1725,7 @@ namespace AsmParserx8664
 
         void addLabel ( char* id )
         {
-            insnTemplate << sc->func->mangle() <<  "_" << id;
+            printLabelName(insnTemplate, sc->func->mangle(), id);
         }
 
         /* Determines whether the operand is a register, memory reference

gen/asmstmt.cpp

@@ -561,7 +561,8 @@ void AsmBlockStatement::toIR(IRState* p)
         // we use a simple static counter to make sure the new end labels are unique
         static size_t uniqueLabelsId = 0;
         std::ostringstream asmGotoEndLabel;
-        asmGotoEndLabel << "." << fdmangle << "__llvm_asm_end" << uniqueLabelsId++;
+        printLabelName(asmGotoEndLabel, fdmangle, "_llvm_asm_end");
+        asmGotoEndLabel << uniqueLabelsId++;
 
         // initialize the setter statement we're going to build
         IRAsmStmt* outSetterStmt = new IRAsmStmt;
@@ -599,7 +600,8 @@ void AsmBlockStatement::toIR(IRState* p)
 
             // provide an in-asm target for the branch and set value
             Logger::println("statement '%s' references outer label '%s': creating forwarder", a->code.c_str(), a->isBranchToLabel->string);
-            code << fdmangle << '_' << a->isBranchToLabel->string << ":\n\t";
+            printLabelName(code, fdmangle, a->isBranchToLabel->string);
+            code << ":\n\t";
             code << "movl $<<in" << n_goto << ">>, $<<out0>>\n";
             //FIXME: Store the value -> label mapping somewhere, so it can be referenced later
             outSetterStmt->in.push_back(DtoConstUint(n_goto));

gen/llvmhelpers.cpp

@@ -8,6 +8,9 @@
 #include "template.h"
 #include "module.h"
 
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/Target/TargetMachine.h"
+
 #include "gen/tollvm.h"
 #include "gen/irstate.h"
 #include "gen/runtime.h"
@@ -1851,3 +1854,11 @@ void callPostblit(Loc &loc, Expression *exp, LLValue *val)
     }
 }
 #endif
+
+//////////////////////////////////////////////////////////////////////////////////////////
+
+void printLabelName(std::ostream& target, const char* func_mangle, const char* label_name)
+{
+    target << gTargetMachine->getMCAsmInfo()->getPrivateGlobalPrefix() <<
+        func_mangle << "_" << label_name;
+}

gen/llvmhelpers.h

@@ -185,4 +185,6 @@ DValue* DtoCallFunction(Loc& loc, Type* resulttype, DValue* fnval, Expressions*
 
 Type* stripModifiers(Type* type);
 
+void printLabelName(std::ostream& target, const char* func_mangle, const char* label_name);
+
 #endif

gen/naked.cpp

@@ -85,7 +85,8 @@ void LabelStatement::toNakedIR(IRState *p)
     Logger::println("LabelStatement::toNakedIR(): %s", loc.toChars());
     LOG_SCOPE;
 
-    p->nakedAsm << p->func()->decl->mangle() << "_" << ident->toChars() << ":";
+    printLabelName(p->nakedAsm, p->func()->decl->mangle(), ident->toChars());
+    p->nakedAsm << ":";
 
     if (statement)
         statement->toNakedIR(p);

gen/statements.cpp

@@ -1388,10 +1388,10 @@ void LabelStatement::toIR(IRState* p)
     if (p->asmBlock)
     {
         IRAsmStmt* a = new IRAsmStmt;
-        a->code += p->func()->decl->mangle();
-        a->code += "_";
-        a->code += ident->toChars();
-        a->code += ":";
+        std::stringstream label;
+        printLabelName(label, p->func()->decl->mangle(), ident->toChars());
+        label << ":";
+        a->code = label.str();
         p->asmBlock->s.push_back(a);
         p->asmBlock->internalLabels.push_back(ident);