i386: Fix up BFmode comparisons in conditional moves [PR107322]

i386: Fix up BFmode comparisons in conditional moves [PR107322]

As the testcase shows, when cbranchbf4/cstorebf4 patterns are defined,
we can get ICEs for conditional moves.
The problem is that the generic conditional move expansion just calls
prepare_cmp_insn which just checks that such a cbranch<mode>4 exists
and returns directly such comparison and passes it down to the conditional
move optabs.
The following patch fixes it by punting if the comparisons aren't
ix86_fp_comparison_operator (to tell the generic code it should separately
compare) and to handle the promotion of BFmode comparison operands to
SFmode such that comparison is performed in SFmode.

2022-10-21  Jakub Jelinek  <jakub@redhat.com>

	PR target/107322
	* config/i386/i386-expand.cc (ix86_prepare_fp_compare_args): For
	BFmode comparisons promote arguments to SFmode and recurse.
	(ix86_expand_int_movcc, ix86_expand_fp_movcc): Return false early
	if comparison operands are BFmode and operands[1] is not
	ix86_fp_comparison_operator.

	* gcc.target/i386/pr107322.c: New test.