[PATCH] Fix cond updating in tree-ssa-dom (PR tree-optimization/77454)

[Jakub Jelinek]

Hi!

The following testcase ICEs because SSA_NAME IMM links are broken.
I've tracked it to DOM's optimize_stmt, a GIMPLE_COND in there is
changed, marked as modified, then in optimize_stmt
  if (gimple_modified_p (stmt) || modified_p)
    {
      tree val = NULL;

      update_stmt_if_modified (stmt);
and a few lines later changed again:
              if (gimple_code (stmt) == GIMPLE_COND)
                {
                  if (integer_zerop (val))
                    gimple_cond_make_false (as_a <gcond *> (stmt));
                  else if (integer_onep (val))
                    gimple_cond_make_true (as_a <gcond *> (stmt));
without update_stmt.  As this is a function which update_stmt_if_modified
a few lines before, I think it is fine to update_stmt it immediately.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2016-09-13  Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/77454
        * tree-ssa-dom.c (optimize_stmt): Call update_stmt after changing
        GIMPLE_COND.  Formatting fix.

        * gcc.dg/pr77454.c: New test.

--- gcc/tree-ssa-dom.c.jj       2016-07-22 15:55:30.000000000 +0200
+++ gcc/tree-ssa-dom.c  2016-09-09 12:29:28.006188533 +0200
@@ -1927,8 +1927,9 @@ optimize_stmt (basic_block bb, gimple_st
 
       if (gimple_code (stmt) == GIMPLE_COND)
         val = fold_binary_loc (gimple_location (stmt),
-                          gimple_cond_code (stmt), boolean_type_node,
-                           gimple_cond_lhs (stmt),  gimple_cond_rhs (stmt));
+                              gimple_cond_code (stmt), boolean_type_node,
+                              gimple_cond_lhs (stmt),
+                              gimple_cond_rhs (stmt));
       else if (gswitch *swtch_stmt = dyn_cast <gswitch *> (stmt))
        val = gimple_switch_index (swtch_stmt);
 
@@ -1946,6 +1947,8 @@ optimize_stmt (basic_block bb, gimple_st
                    gimple_cond_make_true (as_a <gcond *> (stmt));
                  else
                    gcc_unreachable ();
+
+                 update_stmt (stmt);
                }
 
              /* Further simplifications may be possible.  */
--- gcc/testsuite/gcc.dg/pr77454.c.jj   2016-09-09 12:34:47.540537483 +0200
+++ gcc/testsuite/gcc.dg/pr77454.c      2016-09-09 12:32:47.000000000 +0200
@@ -0,0 +1,28 @@
+/* PR tree-optimization/77454 */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+void
+foo (unsigned char x, char y)
+{
+  while (x != 0)
+    {
+      unsigned char *a = &x;
+      int b;
+
+      if (y != 0)
+       a = (unsigned char *) &y;
+      else if (y + 1 != 0)
+       a = (unsigned char *) &y;
+      for (x = 0; x < 1; ++x)
+       b = 0;
+      for (y = 0; y < 3; ++y)
+       {
+         y = !!y;
+         if (y != 0)
+           x = y;
+       }
+      if ((b != 0 ? -1 : *a) < (y = b))
+       b = 1;
+    }
+}

        Jakub