Wrap .subsections_via_symbols directives in #if __APPLE__

[rnk]

Maybe define a macro that completely wraps .subsections_via_symbols for
cleanliness?

[jroelofs]

Reed, care to bikeshed on a name? I'm drawing a blank.

Another option I considered was to add FILE_LEVEL_DIRECTIVE to the definition of DEFINE_COMPILERRT_PRIVATE_FUNCTION (just like DEFINE_COMPILERRT_FUNCTION has), and delete all of these. I'm not sure if that is correct though as there are a few other builtins that don't have .subsections_via_symbols.

[compnerd]

I think that adding that to DEFINE_COMPILERRT_PRIVATE_FUNCTION should be
okay. The only place that this is used currently is when you are defining
a private function.

[jroelofs]

Move .subsections_via_symbols into definition of DEFINE_COMPILERRT_PRIVATE_FUNCTION.

[jroelofs]

Committed r208603.

lib/builtins/arm/restore_vfp_d8_d15_regs.S

   bx      lr                      // return to prolog
 END_COMPILERRT_FUNCTION(__restore_vfp_d8_d15_regs)
 
-  // tell linker it can break up file at label boundaries
-  .subsections_via_symbols

lib/builtins/arm/save_vfp_d8_d15_regs.S

   bx      lr                      // return to prolog
 END_COMPILERRT_FUNCTION(__save_vfp_d8_d15_regs)
 
-  // tell linker it can break up file at label boundaries
-  .subsections_via_symbols

lib/builtins/arm/switch16.S

   bx      ip                      // jump to computed label
 END_COMPILERRT_FUNCTION(__switch16)
 
-  // tell linker it can break up file at label boundaries
-  .subsections_via_symbols

lib/builtins/arm/switch32.S

   bx      ip                       // jump to computed label
 END_COMPILERRT_FUNCTION(__switch32)
 
-  // tell linker it can break up file at label boundaries
-  .subsections_via_symbols
-

lib/builtins/arm/switch8.S

   bx      ip                      // jump to computed label
 END_COMPILERRT_FUNCTION(__switch8)
 
-  // tell linker it can break up file at label boundaries
-  .subsections_via_symbols
-

lib/builtins/arm/switchu8.S

   bx      ip                      // jump to computed label
 END_COMPILERRT_FUNCTION(__switchu8)
 
-  // tell linker it can break up file at label boundaries
-  .subsections_via_symbols
-

lib/builtins/assembly.h

 #if defined(__APPLE__)
 #define HIDDEN_DIRECTIVE .private_extern
 #define LOCAL_LABEL(name) L_##name
+// tell linker it can break up file at label boundaries
 #define FILE_LEVEL_DIRECTIVE  .subsections_via_symbols
 #define SYMBOL_IS_FUNC(name)
 #else

   SYMBOL_NAME(name):
 
 #define DEFINE_COMPILERRT_PRIVATE_FUNCTION(name)           \
+  FILE_LEVEL_DIRECTIVE     SEPARATOR                       \
   .globl SYMBOL_NAME(name) SEPARATOR                       \
   SYMBOL_IS_FUNC(SYMBOL_NAME(name)) SEPARATOR              \
   HIDDEN_DIRECTIVE SYMBOL_NAME(name) SEPARATOR             \