[PATCH, PPC] Fix PR88343.

[Iain Sandoe]

Hi,

The PR is about unnecessary saves of the pic base register, it shows on m32 
Linux and m32/m64 Darwin.

The fix is to check that we are in a pic mode and that the picbase has actually 
been used.
As a bonus, some #ifdef’d TARGET_MACHO code is no longer required.

Tested on power7, bootstrapped on Darwin (testing continues).

OK for trunk?

Branches?

Iain

2018-xx-xx  Segher Boessenkool  <seg...@kernel.crashing.org>
           Iain Sandoe  <i...@sandoe.co.uk>

gcc/
        * config/rs6000/rs6000.c (save_reg_p): Do not save the picbase reg
        unless it has been used.  (first_reg_to_save): Remove dead code.


diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index dfd5303..380cf9d 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -23961,7 +23961,7 @@ save_reg_p (int reg)
        return true;
 
       if ((DEFAULT_ABI == ABI_V4 || DEFAULT_ABI == ABI_DARWIN)
-         && flag_pic)
+         && flag_pic && crtl->uses_pic_offset_table)
        return true;
     }
 
@@ -23981,13 +23981,6 @@ first_reg_to_save (void)
     if (save_reg_p (first_reg))
       break;
 
-#if TARGET_MACHO
-  if (flag_pic
-      && crtl->uses_pic_offset_table
-      && first_reg > RS6000_PIC_OFFSET_TABLE_REGNUM)
-    return RS6000_PIC_OFFSET_TABLE_REGNUM;
-#endif
-
   return first_reg;
 }