rs6000: Rework vector float comparison in rs6000_emit_vector_compare - p4

rs6000: Rework vector float comparison in rs6000_emit_vector_compare - p4

All kinds of vector float comparison operators have been
supported in a rtl comparison pattern as vector.md, we can
just emit an rtx comparison insn with the given comparison
operator in function rs6000_emit_vector_compare instead of
checking and handling the reverse condition cases.

This is part 4, it further checks for comparison opeators
LT/UNGE.  In rs6000_emit_vector_compare, for the handling
of LT, it switches to use code GT, swaps operands and try
again, it's exactly the same as what we have in vector.md:

; lt(a,b)   = gt(b,a)

As to UNGE, in rs6000_emit_vector_compare, it uses reversed
code LT and further operates on the result with one_cmpl,
it's also the same as what's in vector.md:

; unge(a,b) = ~lt(a,b)

This patch should not have any functionality change too.

gcc/ChangeLog:

	* config/rs6000/rs6000.cc (rs6000_emit_vector_compare_inner): Emit rtx
	comparison for operators LT/UNGE of MODE_VECTOR_FLOAT directly.
	(rs6000_emit_vector_compare): Move assertion of no MODE_VECTOR_FLOAT to
	function beginning.