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[avr] minor tweaks for 8-bit operations

Message ID 3c05a06c-444c-cc51-8cb5-0ab50fd8a98b@gjlay.de
State New
Headers show

Commit Message

Georg-Johann Lay July 29, 2016, 4:14 p.m. UTC 
On 14.07.2016 08:36, Denis Chertykov wrote:
> 2016-07-13 14:12 GMT+03:00 Georg-Johann Lay <avr@gjlay.de>:
>>
>> This patch contains some unrelated tweaks
>>
>> - Supplying no-ldregs variant for andqi3, iorqi3 where a const_int mask affects only 1 bit
>>
>> - Some patterns that match situations with zero_extend that can be performed with less instructions / register pressure.
>>
>> - comparing HI against -1
>>
>> Ok for trunk?
>>
>> Johann
>>
>>
>> gcc/
>>         Minor tweaks for QImode.
>>
>>         * config/avr/predicates.md (const_m255_to_m1_operand): New.
>>         * config/avr/constraints.md (Cn8, Ca1, Co1, Yx2): New constraints.
>>         * config/avr/avr.md (add<mode>3) <ALL1>: Make "r,0,r" more
>>         expensive.
>>         (*cmphi.zero-extend.0, *cmphi.zero-extend.1)
>>         (*usum_widenqihi3, *udiff_widenqihi3)
>>         (*addhi3_zero_extend.const): New combiner insns.
>>         (andqi3, iorqi3): Provide "l" (NO_LD_REGS) alternative if
>>         just 1 bit is affected.
>>         * config/avr/avr.c (avr_out_bitop) <QImode>: Don't access xop[3].
>>         (avr_out_compare) [EQ,NE]: Tweak comparing d-regs against -1.
>
>
>
> Please apply.
>

Also applied this addendum; not wrong code but to match the comments.

Johann

	* config/avr/avr.c (avr_out_compare): Use const0_rtx instead of 0
	when testing for compares against constants of the form 0xabab.
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Patch

Index: config/avr/avr.c
===================================================================
--- config/avr/avr.c    (revision 238878)
+++ config/avr/avr.c    (revision 238879)
@@ -5357,7 +5357,7 @@  avr_out_compare (rtx_insn *insn, rtx *xo
       the constant is of the form 0xabab.  */

    if (n_bytes == 2
-      && xval != 0
+      && xval != const0_rtx
        && test_hard_reg_class (LD_REGS, xreg)
        && compare_eq_p (insn)
        && !reg_unused_after (insn, xreg))