i386: Use SBB more [PR94650]

i386: Use SBB more [PR94650]

When returning 0 or -1, "SBB reg,reg" instruction that borrows carry
flag can be used.  Carry flag can be generated by converting compare
with zero to a LTU compare with one, so e.g.

	return -(x == 0)

generates:

        cmpq    $1, %rdi
        sbbq    %rax, %rax

instead of:

        xorl    %eax, %eax
        testq   %rdi, %rdi
        sete    %al
        negq    %rax

A similar conversion can be used for

	return -(x != 0)

where NEG insn can be used instead of compare.  According to x86 ISA,
NEG insn sets carry flag when the source operand is != 0, resulting in:

        negq    %rdi
        sbbq    %rax, %rax

The conversion avoids partial register stall with SETcc instructions.

	PR target/94795
	* config/i386/i386.md (*neg<mode>_ccc): New insn pattern.
	(EQ compare->LTU compare splitter): New splitter.
	(NE compare->NEG splitter): Ditto.

testsuite/ChangeLog:

	PR target/94795
	* gcc.target/i386/pr94795-1.c: New test.
	* gcc.target/i386/pr94795-2.c: New test.