emit x86 get_pc thunks to linkonce sections

[Richard Henderson <rth at redhat dot com>]

We tried this once before, but ran into binutils issues with assembler
private ".L" names in the linkonce sections.  Now we have .hidden which
can properly prevent the name from being used across DSO boundaries
without triggering the old binutils bug.

This only saves 320 bytes from cc1 when compiled -fpic, but that's 
because we have lots of functions within each object file, which 
means that most of the thunks were shared anyway.

It's worth a bit more than 3k from libc.so.


r~


        * config/i386/i386.c (USE_HIDDEN_LINKONCE): New.
        (get_pc_thunk_name): New.
        (output_set_got): Use it.
        (ix86_asm_file_end): If USE_HIDDEN_LINKONCE, emit get_pc thunks
        into linkonce sections.

Index: i386.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/config/i386/i386.c,v
retrieving revision 1.414
diff -c -p -d -r1.414 i386.c
*** i386.c	29 May 2002 20:53:55 -0000	1.414
--- i386.c	29 May 2002 23:06:09 -0000
*************** static rtx ix86_expand_int_compare PARAM
*** 672,677 ****
--- 672,678 ----
  static enum rtx_code ix86_prepare_fp_compare_args PARAMS ((enum rtx_code,
  							   rtx *, rtx *));
  static rtx get_thread_pointer PARAMS ((void));
+ static void get_pc_thunk_name PARAMS ((char [32], unsigned int));
  static rtx gen_push PARAMS ((rtx));
  static int memory_address_length PARAMS ((rtx addr));
  static int ix86_flags_dependant PARAMS ((rtx, rtx, enum attr_type));
*************** ix86_setup_frame_addresses ()
*** 3898,3905 ****
--- 3899,3927 ----
    cfun->machine->accesses_prev_frame = 1;
  }
  
+ #if defined(HAVE_GAS_HIDDEN) && defined(SUPPORTS_ONE_ONLY)
+ # define USE_HIDDEN_LINKONCE 1
+ #else
+ # define USE_HIDDEN_LINKONCE 0
+ #endif
+ 
  static int pic_labels_used;
  
+ /* Fills in the label name that should be used for a pc thunk for
+    the given register.  */
+ 
+ static void
+ get_pc_thunk_name (name, regno)
+      char name[32];
+      unsigned int regno;
+ {
+   if (USE_HIDDEN_LINKONCE)
+     sprintf (name, "__i686.get_pc_thunk.%s", reg_names[regno]);
+   else
+     ASM_GENERATE_INTERNAL_LABEL (name, "LPR", regno);
+ }
+ 
+ 
  /* This function generates code for -fpic that loads %ebx with
     the return address of the caller and then returns.  */
  
*************** ix86_asm_file_end (file)
*** 3912,3929 ****
  
    for (regno = 0; regno < 8; ++regno)
      {
        if (! ((pic_labels_used >> regno) & 1))
  	continue;
  
!       text_section ();
  
!       /* This used to call ASM_DECLARE_FUNCTION_NAME() but since it's an
! 	 internal (non-global) label that's being emitted, it didn't make
! 	 sense to have .type information for local labels.   This caused
! 	 the SCO OpenServer 5.0.4 ELF assembler grief (why are you giving
! 	 me debug info for a label that you're declaring non-global?) this
! 	 was changed to call ASM_OUTPUT_LABEL() instead.  */
!       ASM_OUTPUT_INTERNAL_LABEL (file, "LPR", regno);
  
        xops[0] = gen_rtx_REG (SImode, regno);
        xops[1] = gen_rtx_MEM (SImode, stack_pointer_rtx);
--- 3934,3970 ----
  
    for (regno = 0; regno < 8; ++regno)
      {
+       char name[32];
+ 
        if (! ((pic_labels_used >> regno) & 1))
  	continue;
  
!       get_pc_thunk_name (name, regno);
  
!       if (USE_HIDDEN_LINKONCE)
! 	{
! 	  tree decl;
! 
! 	  decl = build_decl (FUNCTION_DECL, get_identifier (name),
! 			     error_mark_node);
! 	  TREE_PUBLIC (decl) = 1;
! 	  TREE_STATIC (decl) = 1;
! 	  DECL_ONE_ONLY (decl) = 1;
! 
! 	  (*targetm.asm_out.unique_section) (decl, 0);
! 	  named_section (decl, NULL, 0);
! 
! 	  ASM_GLOBALIZE_LABEL (file, name);
! 	  fputs ("\t.hidden\t", file);
! 	  assemble_name (file, name);
! 	  fputc ('\n', file);
! 	  ASM_DECLARE_FUNCTION_NAME (file, name, decl);
! 	}
!       else
! 	{
! 	  text_section ();
! 	  ASM_OUTPUT_LABEL (file, name);
! 	}
  
        xops[0] = gen_rtx_REG (SImode, regno);
        xops[1] = gen_rtx_MEM (SImode, stack_pointer_rtx);
*************** output_set_got (dest)
*** 3960,3970 ****
      }
    else
      {
!       char pic_label_name[32];
!       ASM_GENERATE_INTERNAL_LABEL (pic_label_name, "LPR", REGNO (dest));
        pic_labels_used |= 1 << REGNO (dest);
  
!       xops[2] = gen_rtx_SYMBOL_REF (Pmode, ggc_strdup (pic_label_name));
        xops[2] = gen_rtx_MEM (QImode, xops[2]);
        output_asm_insn ("call\t%X2", xops);
      }
--- 4001,4011 ----
      }
    else
      {
!       char name[32];
!       get_pc_thunk_name (name, REGNO (dest));
        pic_labels_used |= 1 << REGNO (dest);
  
!       xops[2] = gen_rtx_SYMBOL_REF (Pmode, ggc_strdup (name));
        xops[2] = gen_rtx_MEM (QImode, xops[2]);
        output_asm_insn ("call\t%X2", xops);
      }