target-i386: Rewrite gen_enter inline

Use gen_lea_v_seg for centralized segment base knowledge.  Unify
code across 32- and 64-bit.  Fix note about "must save state"
before using the out-of-line helpers.

Signed-off-by: Richard Henderson <rth@twiddle.net>
target-i386: Introduce mo_stacksize

Centralize computation of a MO_SIZE for the stack pointer.

Signed-off-by: Richard Henderson <rth@twiddle.net>
target-i386: Rewrite leave

Unify the code across stack pointer widths.  Fix the note about
not updating ESP before the potential exception.

Signed-off-by: Richard Henderson <rth@twiddle.net>
target-i386: Remove gen_op_mov_reg_T0

Replace with its definition, via Coccinelle.

Signed-off-by: Richard Henderson <rth@twiddle.net>
target-i386: Remove gen_op_mov_reg_T1

Replace with its definition, via Coccinelle.

Signed-off-by: Richard Henderson <rth@twiddle.net>
target-i386: Remove gen_op_addl_T0_T1

Replace with its definition, via Coccinelle.

Signed-off-by: Richard Henderson <rth@twiddle.net>
target-i386: Remove gen_op_mov_TN_reg

Replace with its definition, via Coccinelle.

Signed-off-by: Richard Henderson <rth@twiddle.net>
target-i386: Remove gen_op_mov_reg_A0

Replace with its definition.

Signed-off-by: Richard Henderson <rth@twiddle.net>
target-i386: Remove gen_op_movl_A0_reg

No longer used.

Signed-off-by: Richard Henderson <rth@twiddle.net>
target-i386: Tidy gen_add_A0_im

Merge gen_op_addl_A0_im and gen_op_addq_A0_im into gen_add_A0_im
and clean up the ifdef.

Replace the one remaining user of gen_op_addl_A0_im with gen_add_A0_im.

Signed-off-by: Richard Henderson <rth@twiddle.net>
target-i386: Tidy some size computation

Clean up relics of multiple size domains: - MO_16 + 1 => - 1 + 1 => 0.

Signed-off-by: Richard Henderson <rth@twiddle.net>
target-i386: Rename gen_op_jmp_T0 to gen_op_jmp_v

And make the destination argument explicit.

Signed-off-by: Richard Henderson <rth@twiddle.net>
target-i386: Tidy ljmp

Remove an unnecessary move opcode.

Signed-off-by: Richard Henderson <rth@twiddle.net>
target-i386: Deconstruct the cpu_T array

All references to cpu_T are done with a constant index.  It aids
readability to decompose the array into two scalar variables.

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