[PATCH] Fix ICE with -fno-if-conversion (PR rtl-optimization/68730)

[Jakub Jelinek]

Hi!

It seems some passes in between the combiner and ira aren't prepared to
update dominance info.  It usually is not a problem, because already before
the combiner we call free_dominance_info.  But we now have a new i?86
stv pass that is injected after the combiner that computes dominators but
does not free them.

So, to fix ICE on the following testcase, we can either do what the patch
does, or could conditionalize both the calculate_dominance_info and
free_dominance_info in the convert_scalars_to_vector function (stv pass)
on the dominance info not being computed (like other places in gcc do),
or we could stick free_dominance_info into all passes that break the
dominators just in case it would be computed (out_of_cfglayout is one
example).

Bootstrapped/regtested on x86_64-linux and i686-linux, is this ok for trunk
(or some other variant is preferrable)?

2015-12-10  Jakub Jelinek  <ja...@redhat.com>

        PR rtl-optimization/68730
        * config/i386/i386.c (convert_scalars_to_vector): Call
        free_dominance_info at the end.

        * gcc.dg/pr68730.c: New test.

--- gcc/config/i386/i386.c.jj   2015-12-09 14:39:02.000000000 +0100
+++ gcc/config/i386/i386.c      2015-12-10 12:15:59.517609392 +0100
@@ -3577,6 +3577,7 @@ convert_scalars_to_vector ()
   BITMAP_FREE (candidates);
   bitmap_obstack_release (NULL);
   df_process_deferred_rescans ();
+  free_dominance_info (CDI_DOMINATORS);
 
   /* Conversion means we may have 128bit register spills/fills
      which require aligned stack.  */
--- gcc/testsuite/gcc.dg/pr68730.c.jj   2015-12-10 12:22:07.330365019 +0100
+++ gcc/testsuite/gcc.dg/pr68730.c      2015-12-10 12:24:03.908702426 +0100
@@ -0,0 +1,51 @@
+/* PR rtl-optimization/68730 */
+/* { dg-do compile } */
+/* { dg-options "-O3 -fno-if-conversion" } */
+/* { dg-additional-options "-march=x86-64" { target { i?86-*-* x86_64-*-* } } 
} */
+
+int b, d, e;
+unsigned long long c = 4100543410106915;
+
+void
+foo (void)
+{
+  short f, g = 4 % c;
+  int h = c;
+  if (h)
+    {
+      int i = ~c;
+      if (~c)
+       i = 25662;
+      f = g = i;
+      h = c - g + ~-f;
+      c = ~(c * h - f);
+    }
+  f = g;
+  unsigned long long k = g || c;
+  short l = c ^ g ^ k;
+  if (g > 25662 || c == 74074520320 || !(g < 2))
+    {
+      k = c;
+      l = g;
+      c = ~((k && c) + ~l);
+      f = ~(f * (c ^ k) | l);
+      if (c > k)
+       __builtin_printf ("%d\n", f);
+    }
+  short m = -f;
+  unsigned long long n = c;
+  c = m * f | n % c;
+  if (n)
+    __builtin_printf ("%d\n", f);
+  while (f < -31807)
+    ;
+  c = ~(n | c) | f;
+  if (n < c)
+    __builtin_printf ("%lld\n", (long long) f);
+  for (; d;)
+    for (; e;)
+      for (;;)
+       ;
+  c = h;
+  c = l % c;
+}

        Jakub