------- Comment #2 from rguenth at gcc dot gnu dot org 2010-04-27 09:33 -------
(In reply to comment #1)
> Some further investigation shows that there is code in expand_expr_real_2 that
> is supposed to be able to generate multiply-accumulate instructions, but it
> isn't general enough. In my gimple, I have
> D.1999_10 = D.1998_9 * D.1996_7;
> total_11 = total_19 + D.1999_10;
> The code in expr.c does
> - if ((TREE_CODE (type) == INTEGER_TYPE
>
> - || TREE_CODE (type) == FIXED_POINT_TYPE)
>
> - && (subexp0_def = get_def_for_expr (treeop0,
> - MULT_EXPR)))
> which fails because the multiply operand is treeop1 not treeop0. We need to
> check both operands for the multiply here. I have an initial patch that needs
> testing.
For more general optimization you might want to move all this code to
the tree pass before expansion that detects widening multiplication.
The DOT_PROD_EXPR tree code can be used to carry the information to
the expander.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Last reconfirmed|0000-00-00 00:00:00 |2010-04-27 09:33:19
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43902
