Some additional ix86_rtx_costs clean-ups: NEG, AND, andn and pandn.

Some additional ix86_rtx_costs clean-ups: NEG, AND, andn and pandn.

Double-word NOT requires two operations, but double-word NEG requires
three operations.  Using SSE, vector NOT requires a pxor with -1, but
AND of NOT is cheap thanks to the existence of pandn.  There's also some
legacy (aka incorrect) logic explicitly testing for DImode [independently
of TARGET_64BIT] in determining the cost of logic operations that's not
required.

2022-05-23  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	* config/i386/i386.cc (ix86_rtx_costs) <case AND>: Split from
	XOR/IOR case.  Account for two instructions for double-word
	operations.  In case of vector pandn, account for single
	instruction.  Likewise for integer andn with TARGET_BMI.
	<case NOT>: Vector NOT requires more than 1 instruction (pxor).
	<case NEG>: Double-word negation requires 3 instructions.