[Bug middle-end/30338] [4.3 Regression] infinite loop in maybe_canonicalize_comparison

["rguenth at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #5 from rguenth at gcc dot gnu dot org  2006-12-31 12:57 -------
It starts as we try to fold

  ~(grub_scratch_mem.1_5 + 2097152) > 2147483647

from n_of_executions_at_most.  The problem is we have here already
a type-mismatch:

(gdb) call debug_tree (op0)
 <bit_not_expr 0xb7c20720
    type <integer_type 0xb7b9a2e0 unsigned int public unsigned SI
        size <integer_cst 0xb7b893f0 constant invariant 32>
        unit size <integer_cst 0xb7b89180 constant invariant 4>
        align 32 symtab 0 alias set -1 precision 32 min <integer_cst 0xb7b89468
0> max <integer_cst 0xb7b89450 4294967295>>

    arg 0 <plus_expr 0xb7b909fc
        type <integer_type 0xb7b9a284 int sizes-gimplified public SI size
<integer_cst 0xb7b893f0 32> unit size <integer_cst 0xb7b89180 4>
            align 32 symtab 0 alias set -1 precision 32 min <integer_cst
0xb7b893a8 -2147483648> max <integer_cst 0xb7b893c0 2147483647>
            pointer_to_this <pointer_type 0xb7b9ac38>>

        arg 0 <ssa_name 0xb7c237b0 type <integer_type 0xb7b9a284 int>
            visited var <var_decl 0xb7b95210 grub_scratch_mem.1> def_stmt
<gimple_modify_stmt 0xb7c27438>
            version 5>
        arg 1 <integer_cst 0xb7c27348 constant invariant 2097152>>>

(unsigned BIT_NOT_EXPR with signed argument.)

We get that from scev_probably_wraps_p () at

      tree extreme = fold_convert (unsigned_type,
                                   upper_bound_in_type (type, type));
      delta = fold_build2 (MINUS_EXPR, unsigned_type, extreme, base);
      step_abs = fold_convert (unsigned_type, step);

through fold_binary

      /* Convert -1 - A to ~A.  */
      if (INTEGRAL_TYPE_P (type)
          && integer_all_onesp (arg0))
        return fold_build1 (BIT_NOT_EXPR, type, arg1);

(that needs to read

        return fold_build1 (BIT_NOT_EXPR, type, op1);

at least, which fixes this PR)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30338