[Bug rtl-optimization/49472] [4.7 regression] Compiler segfault on valid code

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49472

--- Comment #10 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2011-06-21 08:31:22 UTC ---
> --- gcc/simplify-rtx.c.jj    2011-06-08 08:53:15.000000000 +0200
> +++ gcc/simplify-rtx.c    2011-06-21 09:46:27.000000000 +0200
> @@ -686,13 +686,13 @@ simplify_unary_operation_1 (enum rtx_cod
>        return simplify_gen_binary (MINUS, mode, temp, XEXP (op, 1));
>      }
> 
> -      /* (neg (mult A B)) becomes (mult (neg A) B).
> +      /* (neg (mult A B)) becomes (mult A (neg B)).
>       This works even for floating-point values.  */
>        if (GET_CODE (op) == MULT
>        && !HONOR_SIGN_DEPENDENT_ROUNDING (mode))
>      {
> -      temp = simplify_gen_unary (NEG, mode, XEXP (op, 0), mode);
> -      return simplify_gen_binary (MULT, mode, temp, XEXP (op, 1));
> +      temp = simplify_gen_unary (NEG, mode, XEXP (op, 1), mode);
> +      return simplify_gen_binary (MULT, mode, XEXP (op, 0), temp);
>      }
> 
>        /* NEG commutes with ASHIFT since it is multiplication.  Only do
> 
> stops the moving of the operands around, with this it keeps being called with
> the same operands again and again, but still an endless recursion.  Eric, any
> preferences where to prevent this from happening?

ISTM that pursuing in the above way, according to swap_commutative_operands_p,
is a sensible approach, so I'd remove the simplify_binary_operation_1 bits.