Re: [PATCH][Revised] Fix PR41313 by restoring original conditional logic for darwin

[Jack Howarth <howarth at bromo dot med dot uc dot edu>]

On Sat, Oct 03, 2009 at 07:58:09PM +0100, IainS wrote:
> actually Jack,
>
> there's a wider issue here.
> the problem appears to be with the profile info generation/use.
>
> I  also see a couple of fails  on C at -m64 (darwin9)
>
> it only happens when there's a suitable .gcda file present.
>
> ==
>
> It is also on more than just one label emit - there are two sections of 
> .eh data with duplicate labels but differing content.
>
> * If the culprit is likely to be darwin_emit_unwind_label() *
>
> Could some kind soul point me at some element in the DECL that would be a 
> candidate for altering the label that's emitted?
>
> (at the moment the function just takes the DECL_ASSEMBLER_NAME, appends 
> ".eh" and then globalizes it)
>
> the function checks for TREE_PUBLIC, and VISIBILITY
> it also checks for a WEAK_DECL.
>
> and finally, appends =0 for empty case.
>
> cheers,
> Iain
>

Iain,
   See PR41313...specifically comment 12. If we take Jakub's approach of fixing
darwin_emit_unwind_label to properly generate different symbols for the hot/cold
partitions, it would appear that we would have to revise both default_emit_unwind_label()
and darwin_emit_unwind_label() to pass additional variables. I have taken a different
approach of returning darwin back to the previous behavior of not supporting hot/cold
partitioning on exceptions. This seems to work fine...

http://gcc.gnu.org/ml/gcc-testresults/2009-10/msg00331.html

The part that I am not having luck with yet is to also leverage the fact that
when targeting 10.6, we don't have to emit eh labels at all. However, I am having
problems wedging this into the existing code.

Index: gcc/config/darwin.c
===================================================================
--- gcc/config/darwin.c (revision 152432)
+++ gcc/config/darwin.c (working copy)
@@ -1697,6 +1697,10 @@
   if (dwarf_strict < 0) 
     dwarf_strict = 1;
 
+  /* Disable .eh labels when targeting >=10.6 to allow -freorder-blocks-and-partition. */
+  if (darwin_macosx_version_min && strverscmp (darwin_macosx_version_min, "10.6") >= 0)
+    targetm.asm_out.unwind_label = default_emit_unwind_label;
+
   if (flag_mkernel || flag_apple_kext)
     {
       /* -mkernel implies -fapple-kext for C++ */

seems insufficient to cause the conditionals...

Index: opts.c
===================================================================
--- opts.c      (revision 152432)
+++ opts.c      (working copy)
@@ -1039,6 +1039,7 @@
 
   if (flag_exceptions && flag_reorder_blocks_and_partition
       && (USING_SJLJ_EXCEPTIONS
+      || (targetm.asm_out.unwind_label != default_emit_unwind_label)
 #ifdef TARGET_UNWIND_INFO
          || 1
 #endif
@@ -1056,6 +1057,7 @@
   if (flag_unwind_tables && ! targetm.unwind_tables_default
       && flag_reorder_blocks_and_partition
       && (USING_SJLJ_EXCEPTIONS
+      || (targetm.asm_out.unwind_label != default_emit_unwind_label)
 #ifdef TARGET_UNWIND_INFO
          || 1
 #endif
@@ -1075,6 +1077,7 @@
       && (!targetm.have_named_sections
          || (flag_unwind_tables && targetm.unwind_tables_default
              && (USING_SJLJ_EXCEPTIONS
+             || (targetm.asm_out.unwind_label != default_emit_unwind_label)
 #ifdef TARGET_UNWIND_INFO
                  || 1
 #endif

to come up false (ie targetm.asm_out.unwind_label = default_emit_unwind_label
when -mmacosx-version-min=10.6. I am very unclear on the exact relationship of
the preprocessor define for TARGET_ASM_EMIT_UNWIND_LABEL and when and how
exactly targetm.asm_out.unwind_label is set to that value.
  Jakub, do you have any comments on how we might effectively reset targetm.asm_out.unwind_label
on the fly? I am attempting to have the compiler, when building for the 10.6 target,
defaults to targetm.asm_out.unwind_label as default_emit_unwind_label but
targeting <10.6, have default_emit_unwind_label set to darwin_emit_unwind_label?
              Jack