tcg-s390: Convert to new ldst opcodes

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-s390: Move ldst helpers out of line

That is, the old LDST_OPTIMIZATION.

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-s390: Use more risbg in the tlb sequence

Elides two insns from the sequence.  Also note the error in the
computation of the parameters for its use as and w/ wraparound.

The resulting tlb compare sequence is satisfyingly minimal:

	risbg  %r2,%r8,51,186,56
	risbg  %r3,%r8,61,178,0
	cg     %r3,904(%r10,%r2)
	lg     %r2,920(%r10,%r2)
	jlh    tlb_miss

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-s390: Implement tcg_register_jit

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-s390: Allow immediate operands to add2 and sub2

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-s390: Improve setcond

There are a variety of common cases for which we can use carry tricks to
avoid a conditional branch.  On very new hardware, use LOAD ON CONDITION
instead of a conditional branch.

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-s390: Don't force -march=z990

While we still require the LONG DISPLACEMENT facility, defaults
have moved on since then.  Don't override the system compiler,
whose default may be set to z9-109 or later.

Signed-off-by: Richard Henderson <rth@twiddle.net>