[Patch,AVR] PR52461: Fix RAMPZ clobbering and RAMP* in epilogue

[Richard Guenther]

On Mon, Mar 5, 2012 at 3:11 PM, Georg-Johann Lay <avr@gjlay.de> wrote:
> Georg-Johann Lay wrote:
>> This patch fixes several issues with RAMP registers:
>>
>> * On Devices with more than 64 KiB RAM, RAMPZ is used as high-byte of
>>   RAM address. If RAMPZ is used to read flash, it must be reset to 0
>>   after the read so that RAM-read will operate correctly in the remainder.
>>   There is no support for RAM > 64 Ki so RAMPZ = 0 is in order.
>>
>> * The ISR epilogue restored RAMP* registers in the wrong order.
>>
>> * As RAMPZ is used both in ELPM and LD/LDD on some xmega core, the right
>>   condition to set RAMPZ prior to ELPM is "have ELPM", not "have RAMPZ".
>>
>> * Never read unintentionally from RAM because a flash address interpreted
>>   as a RAM address might point to the I/O area.
>>
>> Ok for trunk and 4.7?

All commits to the 4.7 branch need explicit release manager approval.  AVR
isn't primary/secondary so please do not change anything before is
released 4.7.0 for it.

Thanks,
Richard.

> The following change in expand_prologue is wrong:
>
> -      if (AVR_HAVE_RAMPZ
> +      if (AVR_HAVE_RAMPD /* sic! */
>
> similar in expand_epilogue.
>
> Ok without that change?
>
>>
>> Johann
>>
>> libgcc/
>>       PR target/52461
>>       * config/avr/lib1funcs.S (__do_copy_data): Clear RAMPZ after usage
>>       if RAMPZ affects reading from RAM.
>>       (__tablejump_elpm__): Ditto.
>>       (.xload): Ditto.
>>       (__movmemx_hi): Ditto.
>>       (__do_global_ctors): Right condition for RAMPZ usage is "have ELPM".
>>       (__do_global_dtors): Ditto.
>>       (__xload_1, __xload_2, __xload_3, __xload_4): Ditto.  And make weak.
>>       (__movmemx_hi): Ditto.  And fix RAM-loop label.
>>       (__xload_1): Never read unintentionally from RAM.
>>
>> gcc/
>>       PR target/52461
>>       * gcc/config/avr/avr.c (expand_prologue): Depend save/restore of
>>       RAMPZ on HAVE_RAMPD, not HAVE_RAMPZ.
>>       (expand_epilogue): Ditto.  And fix order of restoration to:
>>       RAMPZ, RAMPY, RAMPX, RAMPD.
>>       (avr_xload_libgcc_p): Always load __memx by lilbgcc call on
>>       big-RAM devices.
>>       (avr_out_lpm): Clear RAMPZ after usage if RAMPZ affects reading
>>       from RAM.
>>       (avr_out_xload): Never read unintentionally from RAM.
>>       * config/avr/avr.md (xload_8): Adjust insn length.