clang .code16 with -Os producing larger code that it needs to

["Vladimir 'φ-coder/phcoder' Serbinenko" <phcoder@gmail.com>]

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When experimenting with compiling GRUB2 with clang using integrated as,
I found out that it generates a 16-bit code bigger than gas counterpart
and result gets too big for size constraints of bootsector. This was
traced mainly to 2 problems.
32-bit access to 16-bit addresses.
source:
	movl	LOCAL(kernel_sector), %ebx
	movl	%ebx, 8(%si)
clang:
    7cbc:	67 66 8b 1d 5c 7c 00 	addr32 mov 0x7c5c,%ebx
    7cc3:	00
    7cc4:	66 89 5c 08          	mov    %ebx,0x8(%si)

gas:
    7cbc:	66 8b 1e 5c 7c       	mov    0x7c5c,%ebx
    7cc1:	66 89 5c 08          	mov    %ebx,0x8(%si)
32-bit jump.
source:
	jnb	LOCAL(floppy_probe)
clang:
+    7cb5:	66 0f 83 07 01 00 00 	jae    7dc3 <L_floppy_probe>
gas:
-    7cb5:	0f 83 0a 01          	jae    7dc3 <L_floppy_probe>
The last one is particularly problematic as it never makes sense to
issue 32-bit jump if %ip is only 16 bits and it eats 3 extra bytes per
jump. Is it possible to force clang to generate 16-bit jumps?
On bright side if I remove error strings the code is functional.


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