Re: [PATCH (4/7)] Unsigned multiplies using wider signed multiplies

[Andrew Stubbs <andrew dot stubbs at gmail dot com>]

On 07/07/11 11:04, Richard Guenther wrote:
> Both types are equal, so please share the temporary variable you
> create
>
> +         rhs1 = build_and_insert_cast (gsi, gimple_location (stmt),
> +                                       create_tmp_var (type1, NULL),
> rhs1, type1);
> +         rhs2 = build_and_insert_cast (gsi, gimple_location (stmt),
> +                                       create_tmp_var (type2, NULL),
> rhs2, type2);
>
> here (CSE create_tmp_var).

I'm sorry, I don't understand this?

This takes code like this:

  r1 = a;
  r2 = b;
  result = r1 + r2;

And transforms it to this:

  r1 = a;
  r2 = b;
  t1 = (type1) r1;
  t2 = (type2) r2;
  result = t1 + t2;

Yes, type1 == type2, but r1 != r2, so t1 != t2.

I don't see where the common expression is here? But then, I am 
something of a newbie to tree optimizations.

Andrew