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From: "d.g.gorbachev at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/59124] New: [4.8 Regression] Wrong warnings "array subscript is above array bounds"
Date: Thu, 14 Nov 2013 00:44:00 -0000
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X-Bugzilla-Component: tree-optimization
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59124

            Bug ID: 59124
           Summary: [4.8 Regression] Wrong warnings "array subscript is
                    above array bounds"
           Product: gcc
           Version: 4.8.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: d.g.gorbachev at gmail dot com

$ gcc -S -Wall -O3 1.c
1.c: In function 'foo':
1.c:12:23: warning: array subscript is above array bounds [-Warray-bounds]
       bar[j - 1] = baz[j - 1];
                       ^
1.c:12:23: warning: array subscript is above array bounds [-Warray-bounds]

=============== 8< ===============
unsigned baz[6];

void foo(unsigned *bar, unsigned n)
{
  unsigned i, j;

  if (n > 6)
    n = 6;

  for (i = 1; i < n; i++)
    for (j = i - 1; j > 0; j--)
      bar[j - 1] = baz[j - 1];
}
=============== >8 ===============

GCC 4.8.0 20120902 /rev. 190863/ - works,
GCC 4.8.0 20121111 /rev. 193417/ - fails.