[Patch,AVR]: PR49313

[Georg-Johann Lay]

This patch is to finalize the work on PR49313, i.e. better libgcc
implementation of some functions like bswap, counting zeros,
parity and popcount.

These functions are already implemented in libgcc.

This patch now provides a better integration of these functions:
the calls are no more emit as ordinary black box calls by optabs,
instead there are insns to describe the exact register usage of
the functions which are represented as implicit library calls.

This is advantageous because some call-clobbered registers are not
touched and there are more leaf-functions.

Some libgcc functions have minor changes to reduce register
footprint.

Besides that, copysignsf3 is implemented which is easy on avr.

Ok to commit?

Johann


	PR target/49313
	* config/avr/libgcc.S (__ffshi2): Don't skip 2-word instruction.
	(__ctzsi2): Result for 0 may be undefined.
	(__ctzhi2): Result for 0 may be undefined.
	(__popcounthi2): Don't clobber r30. Use __popcounthi2_tail.
	(__popcountsi2): Ditto. And don't clobber r26.
	(__popcountdi2): Ditto. And don't clobber r27.
	* config/avr/avr.md (UNSPEC_COPYSIGN): New c_enum.
	(parityhi2): New expand.
	(paritysi2): New expand.
	(popcounthi2): New expand.
	(popcountsi2): New expand.
	(clzhi2): New expand.
	(clzsi2): New expand.
	(ctzhi2): New expand.
	(ctzsi2): New expand.
	(ffshi2): New expand.
	(ffssi2): New expand.
	(copysignsf2): New insn.
	(bswapsi2): New expand.
	(*parityhi2.libgcc): New insn.
	(*parityqihi2.libgcc): New insn.
	(*paritysihi2.libgcc): New insn.
	(*popcounthi2.libgcc): New insn.
	(*popcountsi2.libgcc): New insn.
	(*popcountqi2.libgcc): New insn.
	(*popcountqihi2.libgcc): New insn-and-split.
	(*clzhi2.libgcc): New insn.
	(*clzsihi2.libgcc): New insn.
	(*ctzhi2.libgcc): New insn.
	(*ctzsihi2.libgcc): New insn.
	(*ffshi2.libgcc): New insn.
	(*ffssihi2.libgcc): New insn.
	(*bswapsi2.libgcc): New insn.
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