Re: [Bug tree-optimization] Fix for PR71994

[kugan]

Hi Richard,

On 26/07/16 21:48, Richard Biener wrote:
On Tue, Jul 26, 2016 at 5:13 AM, kugan
<kugan.vivekanandara...@linaro.org> wrote:
Hi,
For testcase in pr71994, type of bb conditional result and the type of the
PHI stmt are different (as om.0_1 is int and the first PHI argument is
_bool; PHI stmt uses a constant zero that comes from edge 2). Therefore when
we optimize final range test stmt, we end up setting integer 1 for other PHI
argument. This results in ICE.

  <bb 2>:
  om.0_1 = om;
  _2 = om.0_1 >= 0;
  int _3 = (int) _2;
  if (om.0_1 != 0)
    goto <bb 3>;
  else
    goto <bb 4>;

  <bb 3>:
  int _4 = om.0_1 & _3;
  _Bool _12 = _4 != 0;
  <bb 4>:

  # _Bool _13 = PHI <0(2), _12(3)>


IMHO, the fix should be that, we should check the type before replacing the
value (punt otherwise). Attached patch does that. Bootstrapped and
regression tested on x86_64-linux-gnu with no new regressions. Is this OK
for trunk?

Ugh, this is undocumented spaghetti code I am not familiar with.  I
can't see if it
is safe to truncate a constant here so I'd feel safer to just punt instead.


Please see the attached patch,  which now constant truncation. Testing 
in progress. Is this OK for trunk if there is no new regressions?

Thanks,
Kugan

gcc/testsuite/ChangeLog:

2016-07-26  Kugan Vivekanandarajah  <kug...@linaro.org>

        * gcc.dg/torture/pr71994.c: New test.

gcc/ChangeLog:

2016-07-26  Kugan Vivekanandarajah  <kug...@linaro.org>

	* tree-ssa-reassoc.c (maybe_optimize_range_tests): Check type 
compatibility.
diff --git a/gcc/testsuite/gcc.dg/torture/pr71994.c 
b/gcc/testsuite/gcc.dg/torture/pr71994.c
index e69de29..8f5e92c 100644
--- a/gcc/testsuite/gcc.dg/torture/pr71994.c
+++ b/gcc/testsuite/gcc.dg/torture/pr71994.c
@@ -0,0 +1,14 @@
+/* PR tree-optimization/71994 */
+/* { dg-do compile } */
+int om, h6;
+
+void eo (void)
+{
+  const int tl = 1;
+  int ln;
+
+  h6 = (om + tl) > 0;
+  ln = om && (om & h6);
+  h6 = om;
+  om = ln < h6;
+}
diff --git a/gcc/tree-ssa-reassoc.c b/gcc/tree-ssa-reassoc.c
index 18cf978..21742dd 100644
--- a/gcc/tree-ssa-reassoc.c
+++ b/gcc/tree-ssa-reassoc.c
@@ -3636,7 +3636,9 @@ maybe_optimize_range_tests (gimple *stmt)
                  gcc_assert (bb == last_bb);
                  new_op = ops[bbinfo[idx].first_idx++]->op;
                }
-             if (bbinfo[idx].op != new_op)
+             if (bbinfo[idx].op != new_op
+                 && types_compatible_p (TREE_TYPE (new_op),
+                                        TREE_TYPE (bbinfo[idx].op)))
                {
                  imm_use_iterator iter;
                  use_operand_p use_p;