the dwarf3 DW_OP_call_frame_cfa implicitly refers to .debug_frame section.  But 
if we aren't
emitting dwarf unwinding info, it isn't anymore well defined.

There is one target that doesn't emit dwarf unwind info: ia64.  And gdb is not 
able to deal
with DW_OP_call_frame_cfa on ia64, thus breaking -gdwarf-3.

I think the simplest is to disable this opcode for such targets.

Manually tested with gdb on ia64-linux.
No regressions for x86_64-darwin.

Ok for trunk ?


2012-03-14  Tristan Gingold  <ging...@adacore.com>

        * dwarf2out.c (gen_subprogram_die): Require dwarf unwinding to
        use DW_OP_call_frame_cfa.

diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index b5f921a..b43dfcf 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -17485,7 +17485,7 @@ gen_subprogram_die (tree decl, dw_die_ref context_die)
         (3) We can at least reuse the code inspection and interpretation
         code that determines the CFA position at various points in the
         function.  */
-      if (dwarf_version >= 3)
+      if (dwarf_version >= 3 && targetm.debug_unwind_info () == UI_DWARF2)
          dw_loc_descr_ref op = new_loc_descr (DW_OP_call_frame_cfa, 0, 0);
          add_AT_loc (subr_die, DW_AT_frame_base, op);

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