re PR target/19293 (avr-gcc crashes when using shifts with negative shift count)
PR target/19293
PR target/19329
* config/avr/avr.c (notice_update_cc): Only set condition code for
ashrqi3 if shift count > 0.
(out_shift_with_cnt): Handle shift count <= 0 as a no-op.
(ashlqi3_out, ashlhi3_out, ashlsi3_out, ashrqi3_out, ashrhi3_out,
ashrsi3_out, lshrqi3_out, lshrhi3_out, lshrsi3_out): Handle shift
count <= 0 as a no-op, and shift count >= width by copying zero
or sign bit to all bits of the result.
* config/avr/avr.md (all shifts): Add alternatives for zero shift
count, with attribute "length" set to 0 and "cc" set to "none".