[Bug fortran/37131] inline matmul for small matrix sizes

["paul dot richard dot thomas at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

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------- Comment #10 from paul dot richard dot thomas at gmail dot com  2010-06-05 06:55 -------
Subject: Re:  inline matmul for small matrix sizes

Dear Thomas,


> The preferred way would therefore be to state the rank 2 * rank 2 problem as
>
>  do i=1,m
>     do j=1,n
>        c(i,j) = sum(a(i,:) * b(:,j))
>     end do
>  end do
>
> with the inner dot product borrowed using the scalarizer (borrowing
> from dot_product), and the outer loops using either hand-crafted
> TREE code or calling the DO translation.

Yes that is reasonable.  Otherwise, you could borrow a little trick
that I used in allocatable components: trans-array.c:6020

      gfc_add_expr_to_block (&loopbody, tmp);

      /* Build the loop and return.  */
      gfc_init_loopinfo (&loop);
      loop.dimen = 1;
      loop.from[0] = gfc_index_zero_node;
      loop.loopvar[0] = index;
      loop.to[0] = nelems;
      gfc_trans_scalarizing_loops (&loop, &loopbody);
      gfc_add_block_to_block (&fnblock, &loop.pre);

      tmp = gfc_finish_block (&fnblock);
      if (null_cond != NULL_TREE)
        tmp = build3_v (COND_EXPR, null_cond, tmp,
                        build_empty_stmt (input_location));

Here tmp in the first line is the expression or finished block within
the loop.  Earlier on, you will find an expression involving the
index.

Cheers

Paul


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37131