[PATCH] operand_equal_p checking (PR sanitizer/70683)

[Jakub Jelinek]

On Tue, Apr 26, 2016 at 03:02:38PM +0200, Jakub Jelinek wrote:
> The debugging hack is too ugly and slows down the compiler (by artificially
> increasing number of collisions), so it is not appropriate, but perhaps we
> can add some internal only use OEP_* flag, pass it to the recursive calls
> of operand_equal_p and if not set and flag_checking, verify
> iterative_hash_expr equality in the outermost call).

Here is the corresponding checking patch.  It uncovered two further issues
in the tree.[ch] patch which I'm going to post momentarily.
Both patches together bootstrapped/regtested on x86_64-linux and i686-linux,
ok for trunk?

2016-04-27  Jakub Jelinek  <ja...@redhat.com>

        PR sanitizer/70683
        * tree-core.h (enum operand_equal_flag): Add OEP_NO_HASH_CHECK.
        * fold-const.c (operand_equal_p): If flag_checking and
        OEP_NO_HASH_CHECK is not set in flag, recurse with OEP_NO_HASH_CHECK
        and if it returns non-zero, assert iterative_hash_expr on both
        args is the same.

--- gcc/tree-core.h.jj  2016-04-22 18:21:55.000000000 +0200
+++ gcc/tree-core.h     2016-04-26 17:47:19.875753297 +0200
@@ -765,7 +765,9 @@ enum operand_equal_flag {
   OEP_ONLY_CONST = 1,
   OEP_PURE_SAME = 2,
   OEP_MATCH_SIDE_EFFECTS = 4,
-  OEP_ADDRESS_OF = 8
+  OEP_ADDRESS_OF = 8,
+  /* Internal within operand_equal_p:  */
+  OEP_NO_HASH_CHECK = 16
 };
 
 /* Enum and arrays used for tree allocation stats.
--- gcc/fold-const.c.jj 2016-04-22 18:21:32.000000000 +0200
+++ gcc/fold-const.c    2016-04-26 18:30:40.919080701 +0200
@@ -2749,6 +2749,25 @@ combine_comparisons (location_t loc,
 int
 operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags)
 {
+  /* When checking, verify at the outermost operand_equal_p call that
+     if operand_equal_p returns non-zero then ARG0 and ARG1 has the same
+     hash value.  */
+  if (flag_checking && !(flags & OEP_NO_HASH_CHECK))
+    {
+      if (operand_equal_p (arg0, arg1, flags | OEP_NO_HASH_CHECK))
+       {
+         inchash::hash hstate0 (0), hstate1 (0);
+         inchash::add_expr (arg0, hstate0, flags);
+         inchash::add_expr (arg1, hstate1, flags);
+         hashval_t h0 = hstate0.end ();
+         hashval_t h1 = hstate1.end ();
+         gcc_assert (h0 == h1);
+         return 1;
+       }
+      else
+       return 0;
+    }
+
   /* If either is ERROR_MARK, they aren't equal.  */
   if (TREE_CODE (arg0) == ERROR_MARK || TREE_CODE (arg1) == ERROR_MARK
       || TREE_TYPE (arg0) == error_mark_node


        Jakub