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.

gas/config/tc-i386.h

@@ -134,6 +134,7 @@ extern bfd_reloc_code_real_type x86_cons (expressionS *, int);
 extern void x86_cons_fix_new
 (fragS *, unsigned int, unsigned int, expressionS *, bfd_reloc_code_real_type);
 
+#define X_PRECISION     5
 #define X_PRECISION_PAD x86_tfloat_pad ()
 extern int x86_tfloat_pad (void);
 

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}

gas/read.c

@@ -382,10 +382,10 @@ static const pseudo_typeS potable[] = {
   {"ds.b", s_space, 1},
   {"ds.d", s_space, 8},
   {"ds.l", s_space, 4},
-  {"ds.p", s_space, 12},
+  {"ds.p", s_space, 'p'},
   {"ds.s", s_space, 4},
   {"ds.w", s_space, 2},
-  {"ds.x", s_space, 12},
+  {"ds.x", s_space, 'x'},
   {"debug", s_ignore, 0},
 #ifdef S_SET_DESC
   {"desc", s_desc, 0},
@@ -3327,6 +3327,29 @@ s_space (int mult)
   md_flush_pending_output ();
 #endif
 
+  switch (mult)
+    {
+    case 'x':
+#ifdef X_PRECISION
+# ifndef P_PRECISION
+#  define P_PRECISION     X_PRECISION
+#  define P_PRECISION_PAD X_PRECISION_PAD
+# endif
+      mult = (X_PRECISION + X_PRECISION_PAD) * sizeof (LITTLENUM_TYPE);
+      if (!mult)
+#endif
+	mult = 12;
+      break;
+
+    case 'p':
+#ifdef P_PRECISION
+      mult = (P_PRECISION + P_PRECISION_PAD) * sizeof (LITTLENUM_TYPE);
+      if (!mult)
+#endif
+	mult = 12;
+      break;
+    }
+
 #ifdef md_cons_align
   md_cons_align (1);
 #endif

gas/testsuite/gas/i386/fp-elf32.d

@@ -9,4 +9,5 @@ Contents of section .data:
  0010 4f930a40 789a5440 789a5440 00000000  .*
  0020 e65e1710 20395e3b e65e1710 20395e3b  .*
  0030 00000000 0000a044 01000000 0000a044  .*
- 0040 00000000 0000f03f .*
+ 0040 00000000 0000f03f 00000000 00000000  .*
+ 0050 ffffffff ffffffff ffffffff cccccccc  .*

gas/testsuite/gas/i386/fp-elf64.d

@@ -9,4 +9,5 @@ Contents of section .data:
  0010 71a37909 4f930a40 789a5440 789a5440  .*
  0020 e65e1710 20395e3b e65e1710 20395e3b  .*
  0030 00000000 0000a044 01000000 0000a044  .*
- 0040 00000000 0000f03f .*
+ 0040 00000000 0000f03f 00000000 00000000  .*
+ 0050 ffffffff ffffffff ffffffff ffffffff  .*

gas/testsuite/gas/i386/fp.d

@@ -8,4 +8,5 @@ Contents of section .data:
  0010 0a40789a 5440789a 54400000 00000000  .*
  0020 e65e1710 20395e3b e65e1710 20395e3b  .*
  0030 00000000 0000a044 01000000 0000a044  .*
- 0040 00000000 0000f03f .*
+ 0040 00000000 0000f03f 00000000 00000000  .*
+ 0050 ffffffff ffffffff ffffcccc cccccccc  .*

gas/testsuite/gas/i386/fp.s

@@ -20,3 +20,7 @@
 	.double 37778931862957165903873.0
 # Ensure we handle a crazy number of digits
 	.double 1.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
+	.p2align 4,0
+
+	.ds.x 1, -1
+	.p2align 4,0xcc