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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/58791] New: [4.9 Regression] Reassoc reuses SSA_NAMEs
Date: Fri, 18 Oct 2013 16:23:00 -0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 4.9.0
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X-Bugzilla-Who: jakub at gcc dot gnu.org
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58791

            Bug ID: 58791
           Summary: [4.9 Regression] Reassoc reuses SSA_NAMEs
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: jakub at gcc dot gnu.org
          Reporter: jakub at gcc dot gnu.org

volatile char v;

unsigned
foo (unsigned x)
{
  if (x > 7)
    return 0;

  unsigned a = x + 1;
  unsigned b = x + 2;
  unsigned c = a + b;
  unsigned d = 3 * x + 4;
  unsigned e = x + 3;
  unsigned f = d + c + e;
  unsigned a2 = a;
  unsigned b2 = b;
  unsigned c2 = c;
  unsigned d2 = d;
  unsigned e2 = e;
  unsigned f2 = f;
  v++;
  return f;
}

look at -O2 -fdump-tree-reassoc1-alias, the range info is definitely wrong
there for many of the SSA_NAMEs.