[PATCH] Fix PR66870 ppc64le, ppc64 split stack

[Lynn Boger]

Updated changelog and attached patch based on Alan's comments.

gcc/ChangeLog

2015-07-30    Lynn Boger <laboger@linux.vnet.ibm.com>

		PR66870
         	* gcc/config/rs6000/rs6000.c (rs6000_emit_prologue): Check for
         	no_split_stack function attribute along with flag_split_stack.
         	(rs6000_expand_split_stack_prologue): Likewise.


On 7/31/2015 4:00 AM, David Edelsohn wrote:
> On Fri, Jul 31, 2015 at 12:00 AM, Alan Modra <amodra@gmail.com> wrote:
>> On Thu, Jul 30, 2015 at 03:30:12PM -0500, Lynn A. Boger wrote:
>>>                  PR66870
>>>                  * gcc/config/rs6000/rs6000.c:  Add check for no_split_stack
>>>                  function attribute along with flag_split_stack check to
>>>                  determine when to generate split stack prologue for
>>>                  ppc64 and ppc64le.
>> Looks good to me, except that the changelog entry should mention the
>> modified functions, for example:
>>
>>          PR target/66870
>>          * gcc/config/rs6000/rs6000.c (rs6000_emit_prologue): Check for
>>          no_split_stack function attribute along with flag_split_stack.
>>          (rs6000_expand_split_stack_prologue): Likewise.
>>
>> Also, formatting rules for gcc say to not split a line after an
>> operator.
>>
>>> +  int using_split_stack = flag_split_stack &&
>>> +   (lookup_attribute ("no_split_stack", DECL_ATTRIBUTES (cfun->decl))
>>> +         == NULL);
>> The "&&" belongs on the next line, with parentheses added so that emacs
>> and indent will line up the continuation nicely.
>>
>>    int using_split_stack = (flag_split_stack
>>                             && (lookup_attribute ("no_split_stack",
>>                                                   DECL_ATTRIBUTES (cfun->decl))
>>                                 == NULL));
>>
>>
>> David, the following is another piece of the PR66870 fixes.  This
>> stops shrink-wrap from moving insns around in the first few blocks of
>> a function, in a way that is incorrect given that r12 is live.
>> Bootstrapped and regression tested powerpc64le-linux (and
>> powerpc64-linux by Lynn).
>>
>>          PR target/66870
>>          * config/rs6000/rs6000.c (machine_function): Add split_stack_argp_used.
>>          (rs6000_emit_prologue): Set it.
>>          (rs6000_set_up_by_prologue): Specify r12 when split_stack_argp_used.
> Both patches with your suggested changes are okay.
>
> Thanks, David
>
>

-------------- next part --------------
Index: gcc/config/rs6000/rs6000.c
===================================================================
--- gcc/config/rs6000/rs6000.c  (revision 226606)
+++ gcc/config/rs6000/rs6000.c  (working copy)
@@ -23748,6 +23748,11 @@
   int using_static_chain_p = (cfun->static_chain_decl != NULL_TREE
                              && df_regs_ever_live_p (STATIC_CHAIN_REGNUM)
                              && call_used_regs[STATIC_CHAIN_REGNUM]);
+  int using_split_stack = (flag_split_stack
+                           && (lookup_attribute ("no_split_stack",
+                                                 DECL_ATTRIBUTES (cfun->decl))
+                               == NULL));
+ 
   /* Offset to top of frame for frame_reg and sp respectively.  */
   HOST_WIDE_INT frame_off = 0;
   HOST_WIDE_INT sp_off = 0;
@@ -24018,7 +24023,7 @@
       && info->cr_save_p
       && REGNO (frame_reg_rtx) != cr_save_regno
       && !(using_static_chain_p && cr_save_regno == 11)
-      && !(flag_split_stack && cr_save_regno == 12 && sp_adjust))
+      && !(using_split_stack && cr_save_regno == 12 && sp_adjust))
     {
       cr_save_rtx = gen_rtx_REG (SImode, cr_save_regno);
       START_USE (cr_save_regno);
@@ -24596,7 +24601,7 @@
       if ((DEFAULT_ABI == ABI_AIX || DEFAULT_ABI == ABI_ELFv2)
          && !using_static_chain_p)
        save_regno = 11;
-      else if (flag_split_stack || REGNO (frame_reg_rtx) == 12)
+      else if (using_split_stack || REGNO (frame_reg_rtx) == 12)
        {
          save_regno = 11;
          if (using_static_chain_p)
@@ -24699,7 +24704,7 @@
       emit_insn (gen_frame_store (reg, sp_reg_rtx, RS6000_TOC_SAVE_SLOT));
     }
 
-  if (flag_split_stack && split_stack_arg_pointer_used_p ())
+  if (using_split_stack && split_stack_arg_pointer_used_p ())
     {
       /* Set up the arg pointer (r12) for -fsplit-stack code.  If
         __morestack was called, it left the arg pointer to the old
@@ -26287,7 +26292,10 @@
 static rtx
 rs6000_internal_arg_pointer (void)
 {
-  if (flag_split_stack)
+  if (flag_split_stack
+     && (lookup_attribute ("no_split_stack", DECL_ATTRIBUTES (cfun->decl))
+         == NULL))
+
     {
       if (cfun->machine->split_stack_arg_pointer == NULL_RTX)
        {