[Bug target/59797] New: GCC doesn't warn AVX-512 ABI change

[Bug target/59797] New: GCC doesn't warn AVX-512 ABI change

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59797

            Bug ID: 59797
           Summary: GCC doesn't warn AVX-512 ABI change
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hjl.tools at gmail dot com
                CC: kirill.yukhin at intel dot com

[hjl@gnu-6 gcc]$ cat /tmp/z.i
typedef long long __m512i __attribute__ ((__vector_size__ (64),
__may_alias__));

__m512i
f1(__m512i x, __m512i y)
{
  return y;
}
[hjl@gnu-6 gcc]$ ./xgcc -B./ -S -O /tmp/z.i
/tmp/z.i: In function ‘f1’:
/tmp/z.i:4:1: note: The ABI for passing parameters with 64-byte alignment has
changed in GCC 4.6
 f1(__m512i x, __m512i y)
 ^
[hjl@gnu-6 gcc]$ ./xgcc -B./ -S -O /tmp/z.i -mavx512f
[hjl@gnu-6 gcc]$ 

When -mavx512f isn't used, GCC should warn ABI changes for passing/returning
AVX vector values.
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Subject: [Bug target/59797] GCC doesn't warn AVX-512 ABI change
Date: Mon, 13 Jan 2014 22:23:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idY797

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-01-13
   Target Milestone|---                         |4.9.0
     Ever confirmed|0                           |1

[Bug target/59797] GCC doesn't warn AVX-512 ABI change

[kirill.yukhin at intel dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59797

--- Comment #1 from Yukhin Kirill <kirill.yukhin at intel dot com> ---
Sorry, didn't get the problem.

According to output you provided - GCC warns ABI changes

Here is analogue for AVX2:
$ cat 2.c
typedef long long __m256i __attribute__ ((__vector_size__ (32),
__may_alias__));

__m256i
f1(__m256i x, __m256i y)
{
  return y;
}
$ gcc -S 2.c
2.c: In function ‘f1’:
2.c:4:1: note: The ABI for passing parameters with 32-byte alignment has
changed in GCC 4.6
 f1(__m256i x, __m256i y)
 ^
2.c:4:1: warning: AVX vector argument without AVX enabled changes the ABI
[enabled by default]

Difference is that AVX[2] warns about using data types without enabling
AVX2. Is that the case
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Subject: [Bug tree-optimization/59789] [4.9 Regression] ICE in in convert_move, at expr.c:333
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idY789

--- Comment #7 from Alexander Ivchenko <aivchenk at gmail dot com> ---
(In reply to H.J. Lu from comment #3)
> (In reply to Alexander Ivchenko from comment #2)
> > lets just say that my code is valid and I forgot to add "-msse2" :).
> >
>
> Does GCC ICE with -msse2?

No, you were right when you said that the code is incorrect. Seems that I
accidentally found this bug when compiling the initial code without "-msse2".

[Bug target/59797] GCC doesn't warn AVX-512 ABI change

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59797

--- Comment #2 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Yukhin Kirill from comment #1)
> Sorry, didn't get the problem.
> 
> According to output you provided - GCC warns ABI changes
> 
> Here is analogue for AVX2:
> $ cat 2.c
> typedef long long __m256i __attribute__ ((__vector_size__ (32),
> __may_alias__));
> 
> __m256i
> f1(__m256i x, __m256i y)
> {
>   return y;
> }
> $ gcc -S 2.c
> 2.c: In function ‘f1’:
> 2.c:4:1: note: The ABI for passing parameters with 32-byte alignment has
> changed in GCC 4.6

This isn't a ABI change warning.  It just informs users
that GCC has changed ABI in GCC 4.6.

>  f1(__m256i x, __m256i y)
>  ^
> 2.c:4:1: warning: AVX vector argument without AVX enabled changes the ABI
> [enabled by default]

This is the ABI change warning for __m256i when AVX is disabled.

> Difference is that AVX[2] warns about using data types without enabling
> AVX2. Is that the case

We need a similar warning for __m512i when AVX-512 is disabled.
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Subject: [Bug c++/59800] Compilation with g++ fails when -Ofast -flto is used to compile code using some <random> distribution
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idY800

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

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----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
And looking at the libstdc++ code, it indeed has _M_saved initially
uninitialized, and all reads of it guarded by _M_saved_available flag.
Supposedly predicate aware unitialized warning pass isn't able to figure that
out.

[Bug target/59797] GCC doesn't warn AVX-512 ABI change

[ubizjak at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59797
Bug 59797 depends on bug 59794, which changed state.

Bug 59794 Summary: [4.7/4.8 Regression] i386 backend fails to detect MMX/SSE/AVX ABI changes
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59794

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED