[Bug gdb/17464] New: Strange display of vector registers

["muller at ics dot u-strasbg.fr" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=17464

            Bug ID: 17464
           Summary: Strange display of vector registers
           Product: gdb
           Version: unknown
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: muller at ics dot u-strasbg.fr

the command
info vectors
for x86_64 processor
uses hexadecimal formatting.
  This leads to the use of unpack_long function,
and displays only the integer part of
a given float.

Same source as bug report 

$ cat xmm15-problem.c
>>>>>>>>>>>>>>>>>>>>>>>>>>>>Start of source file
#include <math.h>

double
test_xmm14 (double t)
{
  register double x asm ("xmm11");
  register double y asm ("xmm12");
  register double z asm ("xmm14");

  x = 6.7 * t;
  y = 45.234 + t;
  z = y * t + 5.6 * x;
  return z;
}

double
test_xmm15 (double t)
{
  register double x asm ("xmm11");
  register double y asm ("xmm12");
  register double z asm ("xmm15");

  x = 6.7 * t;
  y = 45.234 + t;
  z = y * t + 5.6 * x;
  return z;
}

int
main ()
{
  register double z asm ("xmm15");

  z = 56.8;
  z = test_xmm14 (z);
  z = test_xmm15 (z);
  return 0;
}
>>>>>>>>>>>>>>>>>>>>>>>>>>>>End of source file

$ gdb-mingw64 ./xmm15-problem-mingw64.exe
GNU gdb (GDB) 7.8.50.20141003-cvs
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Type "show configuration" for configuration details.
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For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./xmm15-problem-mingw64.exe...done.
(gdb) start
Temporary breakpoint 1 at 0x40163c: file xmm15-problem.c, line 34.
Starting program: E:\cygwin-32\home\Pierre\test\xmm15-problem-mingw64.exe
[New Thread 8040.0x1f38]

Temporary breakpoint 1, main () at xmm15-problem.c:34
34        z = 56.8;
(gdb) n
35        z = test_xmm14 (z);
(gdb) p z
$1 = 56.799999999999997
(gdb) p &z
Address requested for identifier "z" which is in register $xmm15
(gdb) p $xmm15
$2 = {v4_float = {2.72008302e+023, 3.1937499, 0, 0}, v2_double = {
    56.799999999999997, 0}, v16_int8 = {102, 102, 102, 102, 102, 102, 76, 64,
    0, 0, 0, 0, 0, 0, 0, 0}, v8_int16 = {26214, 26214, 26214, 16460, 0, 0, 0,
    0}, v4_int32 = {1717986918, 1078748774, 0, 0}, v2_int64 = {
    4633190706648082022, 0}, uint128 = 4633190706648082022}
(gdb) inf vec
xmm0           {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x0, 0x0},
  v16_int8 = {0x0 <repeats 16 times>}, v8_int16 = {0x0, 0x0, 0x0, 0x0, 0x0,
    0x0, 0x0, 0x0}, v4_int32 = {0x0, 0x0, 0x0, 0x0}, v2_int64 = {0x0, 0x0},
  uint128 = 0x00000000000000000000000000000000}

.........Other xmm registers removed.
xmm15          {v4_float = {0x0, 0x3, 0x0, 0x0}, v2_double = {0x38, 0x0},
  v16_int8 = {0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x4c, 0x40, 0x0, 0x0, 0x0,
    0x0, 0x0, 0x0, 0x0, 0x0}, v8_int16 = {0x6666, 0x6666, 0x6666, 0x404c,
    0x0, 0x0, 0x0, 0x0}, v4_int32 = {0x66666666, 0x404c6666, 0x0, 0x0},
  v2_int64 = {0x404c666666666666, 0x0},
  uint128 = 0x0000000000000000404c666666666666}

As you can see, the v2_double field,
is written out as {0x38, 0x0}, which corresponds to the
integer part 56 of 56.8.

  It is a pity that the default command to
display vector registers does not give the full information
on the value for floating point fields.

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