[PATCH] Fix eliminate_redundant_comparison (PR tree-optimization/48734)

[Jakub Jelinek]

Hi!

eliminate_redundant_comparison calls maybe_fold_{and,or}_comparisons,
which calls fold.  Expecting that the result is either INTEGER_CST or
a comparison with gimple vals is just bad assumption, fold can create
all kinds of canonicalizations.

While we can perhaps handle a few of them here, I'm slightly worried
to add too much more stuff using build_and_add_sum etc., as that might
increase register pressure.

This patch just gives up if it can't handle it instead of ICEing,
in the future as follow-up we could perhaps handle a few cases.
Given that this ICE hit us only once after so long and never on real-world
code so far, I'd say so it isn't that urgent though.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk/4.6?

2011-04-26  Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/48734
        * tree-ssa-reassoc.c (eliminate_redundant_comparison): Give up
        if return value from maybe_fold_*_comparsions isn't something
        the code is prepared to handle.

        * gcc.c-torture/compile/pr48734.c: New test.

--- gcc/tree-ssa-reassoc.c.jj   2011-02-15 15:42:27.000000000 +0100
+++ gcc/tree-ssa-reassoc.c      2011-04-26 09:32:51.000000000 +0200
@@ -1279,6 +1279,20 @@ eliminate_redundant_comparison (enum tre
       if (!useless_type_conversion_p (TREE_TYPE (curr->op), TREE_TYPE (t)))
        t = fold_convert (TREE_TYPE (curr->op), t);
 
+      if (TREE_CODE (t) != INTEGER_CST
+         && !operand_equal_p (t, curr->op, 0))
+       {
+         enum tree_code subcode;
+         tree newop1, newop2;
+         if (!COMPARISON_CLASS_P (t))
+           continue;
+         extract_ops_from_tree (t, &subcode, &newop1, &newop2);
+         STRIP_USELESS_TYPE_CONVERSION (newop1);
+         STRIP_USELESS_TYPE_CONVERSION (newop2);
+         if (!is_gimple_val (newop1) || !is_gimple_val (newop2))
+           continue;
+       }
+
       if (dump_file && (dump_flags & TDF_DETAILS))
        {
          fprintf (dump_file, "Equivalence: ");
--- gcc/testsuite/gcc.c-torture/compile/pr48734.c.jj    2011-04-26 
09:34:38.000000000 +0200
+++ gcc/testsuite/gcc.c-torture/compile/pr48734.c       2011-04-26 
09:34:17.000000000 +0200
@@ -0,0 +1,11 @@
+/* PR tree-optimization/48734 */
+
+unsigned int
+foo (int x, unsigned int y, unsigned int z)
+{
+  z &= (x == -__INT_MAX__ - 1 ? x : -x) > y;
+  z &= (x == -__INT_MAX__ - 1 ? x : -x) > y;
+  z &= (x == -__INT_MAX__ - 1 ? x : -x) > y;
+  z &= (x == -__INT_MAX__ - 1 ? x : -x) > y;
+  return z;
+}

        Jakub