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[Patch,AVR,4.6]: Fix PR50063 GCC does not support FP = SP

Denis Chertykov wrote:
> 2012/2/21 Richard Henderson:
>> On 02/21/12 09:08, Georg-Johann Lay wrote:
>>>       PR rtl-optimization/50063
>>>       * config/avr/ (movhi_sp_r): Handle -1 (unknown IRQ state)
>>>       and 2 (8-bit SP) in operand 2.
>>>       * config/avr/avr.c (avr_prologue_setup_frame): Adjust prologue
>>>       setup to use movhi_sp_r instead of vanilla move to write SP.
>>>       Adjust REG_CFA notes to superseed unspec.
>>>       (expand_epilogue): Adjust epilogue setup to use read_sp instead
>>>       of vanilla move.
>>>       As function body might contain CLI or SEI: Use irq_state 0 (IRQ
>>>       known to be off) only with TARGET_NO_INTERRUPTS. Never use
>>>       irq_state 1 (IRQ known to be on) here.
>> The CFA bits in avr_prologue_setup_frame look good.
>> I'll let Denis or Eric review the movhi_sp_r change.
> Approved.
> Denis.

Here is a patchlet for 4.6. It just sets -fno-dse to work around the problem
because I think back-porting all what's needed is too much change.

Compiling avr-libc without DSE gives the same sizes for all objects which shows
that this is not a crucial optimization for avr.

Ok for 4.6 branch?


	PR rtl-optimization/50063
	* config/avr/avr.c (avr_option_override): Disable DSE.

Index: config/avr/avr.c
--- config/avr/avr.c    (revision 184460)
+++ config/avr/avr.c    (working copy)
@@ -245,6 +245,11 @@ avr_option_override (void)

   flag_delete_null_pointer_checks = 0;

+  /* Kick off DSE in order to hack around PR rtl-optimization/50063.
+     Backporting all of 4.7 is too much.  */
+  flag_dse = 0;
   for (t = avr_mcu_types; t->name; t++)
     if (strcmp (t->name, avr_mcu_name) == 0)

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