[Bug testsuite/52563] FAIL: gcc.dg/tree-ssa/scev-[3,4].c scan-tree-dump-times optimized "&a" 1

["jiangning.liu at arm dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52563

--- Comment #3 from Jiangning Liu <jiangning.liu at arm dot com> 2012-03-13 08:11:40 UTC ---
First, I tried gcc 4.4.3 on x86-64, and it works for this test case, so it is
to some extension a GCC regression.

Second, I tried trunk, and I can reproduce the failure for this test case. It
means there are still some other bugs hidden after my scalar evolution
improvement on address of array element.

Third, loop ivopt should be able to find &a is the base object of a selected IV
candidate after the analysis from simple_iv. After loop ivopt, I see the
following dump,

Selected IV set:
candidate 5 (important)
  depends on 1
  var_before i_13
  var_after i_6
  original biv
  type int
  base k_2(D)
  step k_2(D)
candidate 6
  depends on 1
  var_before ivtmp.11_9
  var_after ivtmp.11_1
  incremented before exit test
  type unsigned long
  base (unsigned long) ((int *) &a + (sizetype) k_2(D) * 4)
  step (unsigned long) ((sizetype) k_2(D) * 4)
  base object (void *) &a

So &a is already identified as an IV base object, but somehow only one &a is 
hoisted out of loop, while the other one isn't.

<bb 4>:
  D.1728_15 = (sizetype) k_2(D);
  D.1729_16 = D.1728_15 * 4;
  D.1730_17 = (sizetype) k_2(D);
  D.1731_18 = D.1730_17 * 4;
  D.1732_19 = &a + D.1731_18;
  ivtmp.11_20 = (unsigned long) D.1732_19;

<bb 5>:
  # i_13 = PHI <i_6(7), k_2(D)(4)>
  # ivtmp.11_9 = PHI <ivtmp.11_1(7), ivtmp.11_20(4)>
  a_p.0_4 = (int *) ivtmp.11_9;
  MEM[(int *)&a][i_13] = 100;
  i_6 = i_13 + k_2(D);
  ivtmp.11_1 = ivtmp.11_9 + D.1729_16;
  if (i_6 <= 999)
    goto <bb 7>;
  else
    goto <bb 6>;

This statement,

  MEM[(int *)&a][i_13] = 100;

is expected to be like,

  D.4086_21 = (void *) ivtmp.11_9;
  MEM[base: D.4086_21, offset: 0B] = 100;

after loop ivopt.