[PATCH][PR 18702] Fix wrong output of x87 registers due to truncation to double on amd64

[Yao Qi]

Ruslan Kabatsayev <b7.10110111@gmail.com> writes:

Hi Ruslan,

> When `info float` is used on an AMD64 system, GDB prints floating-point
> values of x87 registers with raw contents like 0x361a867a8e0527397ce0 or
> 0xc4f988454a1ddd3cfdab wrongly. This happens due to truncation to double,
> after which the former becomes 0.0, and the latter becomes negative infinity.
> This is caused by failed detection of x86-64 host, which results in setting
> gdb_host_{float,double,long_double}_format to zeros.
> This commit fixes this misdetection.

I think your patch is correct, but I am not confident approving it
because I know few about floating point stuff.  Do you run GDB
regression tests?

>
> gdb/ChangeLog:
>
> 	* configure.host: Fix detection of x86_64 host when setting floatformats

This line is too long, the max is 74.  Sentence should be ended with ".".

-- 
Yao (齐尧)