i386: Use ADD to implement compares with negated operand [PR94913]

i386: Use ADD to implement compares with negated operand [PR94913]

Use carry flag from addition to implement GEU/LTU compares
with negated operand, so e.g.

	~x < y

compiles to:

        addq    %rsi, %rdi
        setc    %al

instead of:

        notq    %rdi
        cmpq    %rsi, %rdi
        setb    %al

	PR target/94913
	* config/i386/predicates.md (add_comparison_operator): New predicate.
	* config/i386/i386.md (compare->add splitter): New splitters.

testsuite/ChangeLog:

	PR target/94913
	* gcc.target/i386/pr94913-1.c: New test.
	* gcc.target/i386/pr94913-2.c: Ditto.