x86/ELF: fix .ds.x output

The ELF psABI-s are quite clear here: On 32-bit the underlying data type
is 12 bytes long (with 2 bytes of trailing padding), while on 64-bit it
is 16 bytes long (with 6 bytes of padding). Make s_space() capable of
handling 'x' (and 'p') type floating point being other than 12 bytes
wide (also adjusting documentation). This requires duplicating the
definition of X_PRECISION in the target speciifc header; the compiler
would complain if this was out of sync with config/atof-ieee.c.

Note that for now padding space doesn't get separated from actual
storage, which means that things will work correctly only for little-
endian cases, and which also means that by specifying large enough
numbers padding space can be set to non-zero. Since the logic is needed
for a single little-endian architecture only for now, I'm hoping that
this might be acceptable for the time being; otherwise the change will
become more intrusive.

Note also that this brings the emitted data size of .ds.x vs .tfloat in
line for non-ELF targets as well; the issue will be even more obvious
when further taking into account a subsequent patch fixing .dc.x/.dcb.x
(where output sizes currently differ depending on input format).

Extend existing x86 testcases.

1 files changed, 2 insertions, 2 deletions

diff --git a/gas/doc/as.texi b/gas/doc/as.texi
index 292c4af2..b8d5b9b 100644
--- a/gas/doc/as.texi
+++ b/gas/doc/as.texi
@@ -5125,13 +5125,13 @@ Emits 8-byte values.
 @item @samp{.l}
 Emits 4-byte values.
 @item @samp{.p}
-Emits 12-byte values.
+Emits values with size matching packed-decimal floating-point ones.
 @item @samp{.s}
 Emits 4-byte values.
 @item @samp{.w}
 Emits 2-byte values.
 @item @samp{.x}
-Emits 12-byte values.
+Emits values with size matching long double precision floating-point ones.
 @end table
 
 Note - unlike the @code{.dcb} directive the @samp{.d}, @samp{.s} and @samp{.x}