[Consult] g++: About "-Wunused-variable" for constant variable initialized by function

2014-10-12 Thread Chen Gang 
Hello All:

I found an issue about g++, it is OK for "-Wall -O0", but will report
-Wunused-variable for "-Wall -O1|2|3|s". The original version (e.g.
gcc 4.8.3 redhat version) does not report warning for "-Wall -O?".

The related operation:

  [root@localhost qemu_cc]# cat test.cc
  const char n() { return 1; }
  const char c =  n();
  [root@localhost qemu_cc]# /usr/local/bin/g++ -Wall -O0 -c -o test.o test.cc
  [root@localhost qemu_cc]# /usr/local/bin/g++ -Wall -O2 -c -o test.o test.cc
  test.cc:2:12: warning: 'c' defined but not used [-Wunused-variable]
   const char c =  n();
  ^

The g++ information:

  [root@localhost qemu_cc]# /usr/local/bin/g++  -v
  Using built-in specs.
  COLLECT_GCC=/usr/local/bin/g++
  
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-unknown-linux-gnu/5.0.0/lto-wrapper
  Target: x86_64-unknown-linux-gnu
  Configured with: ../gcc/configure --disable-multilibs --disable-nls
  Thread model: posix
  gcc version 5.0.0 20141003 (experimental) (GCC) 


If we are sure it is a bug, I shall try to analyze it within this month.

Thanks
-- 
Chen Gang

Open, share, and attitude like air, water, and life which God blessed

Re: RTL infrastructure leaks VALUE expressions into aliasing-detecting functions

2014-10-12 Thread Uros Bizjak 
On Fri, Oct 10, 2014 at 8:37 PM, Uros Bizjak  wrote:

>> Right.  And my question is what happens if we aren't as aggressive here.
>> What happens if before this check we return nonzero if X or Y is a VALUE?
>> Do we then get into memrefs_conflict_p and does it do the right thing?
>
> Following patch just after AND detection in base_alias_check fixes the
> testcase from PR:
>
> --cut here--
> Index: alias.c
> ===
> --- alias.c (revision 216100)
> +++ alias.c (working copy)
> @@ -1842,6 +1842,8 @@ base_alias_check (rtx x, rtx x_base, rtx y, rtx y_
>   || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1
>  return 1;
>
> +  return 1;
> +
>/* Differing symbols not accessed via AND never alias.  */
>if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
>  return 0;
> --cut here--
>
> I have started a bootstrap on alpha native with this patch (it will
> take a day or so) and will report back findings

Yes, this "patch" solves the original gfortran problem.

It looks to me that the code that handles AND addresses in
base_alias_check is not prepared to handle VALUES correctly.

Uros.

gcc-5-20141012 is now available

2014-10-12 Thread gccadmin 
Snapshot gcc-5-20141012 is now available on
  ftp://gcc.gnu.org/pub/gcc/snapshots/5-20141012/
and on various mirrors, see http://gcc.gnu.org/mirrors.html for details.

This snapshot has been generated from the GCC 5 SVN branch
with the following options: svn://gcc.gnu.org/svn/gcc/trunk revision 216127

You'll find:

 gcc-5-20141012.tar.bz2   Complete GCC

  MD5=95691e1088e4143efd311be53a612e93
  SHA1=5d654b8fa4cc56c0baca42b3fc405d0965f4d4e3

Diffs from 5-20141005 are available in the diffs/ subdirectory.

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