match.pd: Optimize .PARITY (.BITREVERSE (x))

match.pd: Optimize .PARITY (.BITREVERSE (x))

When working on the last patch, I've noticed that the parity(bswap(x))
optimization only optimizes the 16/32/64/128-bit bswaps, but not
generic _BitInt bswap, and doesn't optimize any of the bitreverses.
Both all bswap and all bitreverse builtins/ifns preserve values of all the
bits, just permute them, so parity (and popcount too) can be optimized.

2026-07-30  Jakub Jelinek  <jakub@redhat.com>

	* match.pd (parity(bswap(x)) is parity(x)): Use BSWAP BITREVERSE
	instead of BUILT_IN_BSWAP16 BUILT_IN_BSWAP32 BUILT_IN_BSWAP64
	BUILT_IN_BSWAP128.

	* gcc.dg/bitint-140.c: New test.

Reviewed-by: Richard Biener <rguenth@suse.de>