[Patch,avr]: Speed up 64-bit shifts in libgcc

[Georg-Johann Lay]

This patch fixed the speed of 64-bit shifts and rotate.

These operations were implemented by bit-wise shifts and thus the speed is not
reasonable for such basic arithmetic.

The new implementation first shifts byte-wise and only the remaining mod 8 is
shifted bit-wise.

The new methods needs few more instructions, but 64-bit arithmetic needs much
code, anyway...  But base arithmetic should operate reasonably fast and not
take 600 or mote ticks for a simple shift.

Ok for trunk?

Johann


	* config/avr/lib1funcs.S (__ashrdi3, __lshrdi3, __ashldi3)
	(__rotldi3): Shift bytewise if applicable.


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