Re: [PATCH PR71503/PR71683]Fix ICE in tree-if-conv.c

[Bin.Cheng]

On Thu, Jul 14, 2016 at 6:49 PM, Jeff Law <l...@redhat.com> wrote:
> On 07/14/2016 10:12 AM, Bin Cheng wrote:
>>
>> Hi,
>> This is a simple patch fixing ICE in tree-if-conv.c.  Existing code does
>> not setup a variable (cond) when predicate of basic block is true and it
>> asserts on the variable.  Interesting thing is dead code is not cleaned up
>> before ifcvt, but that's another story.
>> Bootstrap and test on x86_64.  Is it OK?
>>
>> Thanks,
>> bin
>>
>> 2016-07-13  Bin Cheng  <bin.ch...@arm.com>
>>
>>         PR tree-optimization/71503
>>         PR tree-optimization/71683
>>         * tree-if-conv.c (gen_phi_arg_condition): Set cond when predicate
>>         is true.
>
> Maybe I'm missing something, but in the case where we COND is already set
> and we encounter a true predicate later, shouldn't that make the result true
> as well?
>
> I don't think the code will though -- we just throw away the true condition.
> ISTM that the right thing to do is
>
> if (is_true_predicate (c))
>   {
>     cond = c;
>     continue;
>   }
>
> Can you see if you can trigger a case where we have an existing cond, then
> later find a true condition to verify the right thing happens?
Hi,
Attachment is the updated patch, it breaks the loop once TRUE
predicate is found.  I also built spec2k6/spec2k and your case is not
found.  Is it OK?

Thanks,
bin

diff --git a/gcc/tree-if-conv.c b/gcc/tree-if-conv.c
index e5a3372..4253d19 100644
--- a/gcc/tree-if-conv.c
+++ b/gcc/tree-if-conv.c
@@ -1687,7 +1687,10 @@ gen_phi_arg_condition (gphi *phi, vec<int> *occur,
       e = gimple_phi_arg_edge (phi, (*occur)[i]);
       c = bb_predicate (e->src);
       if (is_true_predicate (c))
-       continue;
+       {
+         cond = c;
+         break;
+       }
       c = force_gimple_operand_gsi_1 (gsi, unshare_expr (c),
                                      is_gimple_condexpr, NULL_TREE,
                                      true, GSI_SAME_STMT);
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ifc-pr71503.c 
b/gcc/testsuite/gcc.dg/tree-ssa/ifc-pr71503.c
new file mode 100644
index 0000000..5a90abf
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ifc-pr71503.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-Ofast" { target *-*-* } } */
+
+int a, b;
+unsigned long d;
+void fn1() {
+  unsigned long *h = &d;
+line1 : {
+  int i = 4;
+  for (; b; i++) {
+    d = ((d + 6 ?: *h) ? a : 7) && (i &= 0 >= b);
+    b += a;
+  }
+}
+  h = 0;
+  for (; *h;)
+    goto line1;
+}
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ifc-pr71683.c 
b/gcc/testsuite/gcc.dg/tree-ssa/ifc-pr71683.c
new file mode 100644
index 0000000..851be37
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ifc-pr71683.c
@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-options "-Ofast" { target *-*-* } } */
+
+short unsigned int ve;
+
+void
+u1 (void)
+{
+  int oq = 0;
+
+  while (ve != 0)
+    {
+      int j4, w7 = oq;
+
+      oq = 0 / oq;
+      ve %= oq;
+      j4 = ve ^ 1;
+      ve ^= oq;
+      if (j4 != 0 ? j4 : ve)
+        oq = ve;
+      else
+        if (w7 != 0)
+          oq = ve;
+    }
+}