Re: [PATCH] PR libgcc/59714 complex division is surprising on aarch64

[vladimir.mezentsev@oracle.com]

On 02/06/2018 08:53 AM, Joseph Myers wrote:
> The files in libgcc/soft-fp must be verbatim copies of the master sources
> in glibc.  So you can't make any local changes to them, and if you think 
> changes are needed you need to patch things upstream in glibc first, with 
> a proper extended explanation of why the fix is needed and why it is safe 
> and the appropriate design for the fix.  There's nothing at all in this 
> patch submission to explain that change.

It is a bug/typo  in gcc/libgcc/soft-fp/quad.h when _FP_W_TYPE_SIZE is
64 (for example, on aarch64) .
It looks like a code after line 202 was never used.
% cat -n libgcc/soft-fp/quad.h
...
   201   
   202    #else   /* not _FP_W_TYPE_SIZE < 64 */
   203    union _FP_UNION_Q
   204    {
   205      TFtype flt /* __attribute__ ((mode (TF))) */ ;
   206      struct *_FP_STRUCT_LAYOUT*
   207      {
   208        _FP_W_TYPE a, b;
   209      } longs;
   210      struct *_FP_STRUCT_LAYOUT*
   211      {
   212    # if __BYTE_ORDER == __BIG_ENDIAN
   213        unsigned sign    : 1;
   214        unsigned exp     : _FP_EXPBITS_Q;
   215        _FP_W_TYPE frac1 : _FP_FRACBITS_Q - (_FP_IMPLBIT_Q != 0) -
_FP_W_TYPE_SIZE;
   216        _FP_W_TYPE frac0 : _FP_W_TYPE_SIZE;
   217    # else
   218        _FP_W_TYPE frac0 : _FP_W_TYPE_SIZE;
   219        _FP_W_TYPE frac1 : _FP_FRACBITS_Q - (_FP_IMPLBIT_Q != 0) -
_FP_W_TYPE_SIZE;
   220        unsigned exp     : _FP_EXPBITS_Q;
   221        unsigned sign    : 1;
   222    # endif
   223      } bits;
   224    };

We see 'struct _FP_STRUCT_LAYOUT' is declared twice (in lines 206 and
210) inside union _FP_UNION_Q.
Compiler reports warning.


-Vladimir

P.S.:
gcc/libgcc/soft-fp/ and  glibc/soft-fp/ are not synchronized now. For
example:

% diff gcc/libgcc/soft-fp/quad.h  glibc/soft-fp/
3c3
<    Copyright (C) 1997-2016 Free Software Foundation, Inc.
---
>    Copyright (C) 1997-2018 Free Software Foundation, Inc.
96c96
<   } bits __attribute__ ((packed));
---
>   } bits;