[RFA/ARM][Patch 01/02]: Thumb2 epilogue in RTL

[Sameera Deshpande]

Hi Ramana,

Please find attached reworked patch. The patch is tested with check-gcc,
check-gdb and bootstrap with no regression.

On Fri, 2011-10-21 at 13:43 +0100, Ramana Radhakrishnan wrote: 
> Why are you differentiating on stack_only ? Does it really matter ?
> 
The patterns pop_multi* generate pop instruction, hence I wanted to be
sure that base register is stack.

I can remove stack_only option by
1. Modifying pattern to match SP as base-register explicitly or
2. Generate ldm%(ia%) instruction for non-SP base registers.

I chose second option.

> Hmmm isn't this true of only LDM's in Thumb state ? Though it could be argued
> that this patch is only T2 epilogues.
> 
Yes, its true. But for single register we want to match LDR pattern and
not any of ldm* or pop_multi* pattern. So, I am barring LDM for single
register here.

> >+    strcpy (pattern, \"fldmfdd\\t\");
> >+    strcat (pattern,
> >+                    reg_names[REGNO (SET_DEST (XVECEXP (operands[0], 0, 0)))]);
> >+    strcat (pattern, \"!, {\");
> >+    strcat (pattern, table[(REGNO (XEXP (XVECEXP (operands[0], 0, 1), 0))
> >+                           - FIRST_VFP_REGNUM) / 2].name);
> 
> Can't you reuse names from arm.h and avoid the table here ?
> 
The array REGISTER_NAMES in aout.h use S0, S2, ...  names for double
registers. Is there any way to use OVERLAPPING_REGISTER_NAMES? If that
can be done, I can eliminate the table here.

Updated ChangeLog entry:

2011-09-28  Ian Bolton         <ian.bolton@arm.com>
            Sameera Deshpande  <sameera.deshpande@arm.com>
           
       * config/arm/arm-protos.h (load_multiple_operation_p): New
declaration.
         (thumb2_expand_epilogue): Likewise.
         (thumb2_output_return): Likewise
         (thumb2_expand_return): Likewise.
         (thumb_unexpanded_epilogue): Rename to... 
         (thumb1_unexpanded_epilogue): ...this 
       * config/arm/arm.c (load_multiple_operation_p): New function. 
         (thumb2_emit_multi_reg_pop): Likewise.
         (thumb2_emit_vfp_multi_reg_pop): Likewise.
         (thumb2_expand_return): Likewise. 
         (thumb2_expand_epilogue): Likewise. 
         (thumb2_output_return): Likewise
         (thumb_unexpanded_epilogue): Rename to...
         ( thumb1_unexpanded_epilogue): ...this
       * config/arm/arm.md (pop_multiple_with_stack_update): New
pattern. 
         (pop_multiple_with_stack_update_and_return): Likewise.
         (thumb2_ldr_with_return): Likewise.
         (vfp_point_pop_multiple_with_stack_update): Likewise.
         (return): Update condition and code for pattern.
         (arm_return): Likewise.
         (epilogue_insns): Likewise.
       * config/arm/predicates.md (load_multiple_operation): Update
predicate.
         (load_multiple_operation_return): New predicate. 
         (load_multiple_operation_fp): Likewise.
       * config/arm/thumb2.md (thumb2_return): Remove.
         (thumb2_rtl_epilogue_return): New pattern.


- Thanks and regards,
  Sameera D.
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