Re: [PATCH] Expand pow(x,n) into mulitplies in cse_sincos pass (PR46728, patch 2)

[Richard Guenther <richard dot guenther at gmail dot com>]

On Tue, May 24, 2011 at 10:35 PM, William J. Schmidt
<wschmidt@linux.vnet.ibm.com> wrote:
> Here's a small patch to expand pow(x,n) for integer n using the
> powi(x,n) logic in the cse_sincos pass. ?OK for trunk?
>
> For the next patch, I'll plan on expanding pow(x,n) for n in
> {0.5, 0.25, 0.75, 1./3., 1./6.}. ?This logic will be added to
> gimple_expand_builtin_pow.

Ok.

Thanks,
Richard.

> Bill
>
>
> 2011-05-24 ?Bill Schmidt ?<wschmidt@linux.vnet.ibm.com>
> ? ? ? ?PR tree-optimization/46728
> ? ? ? ?* tree-ssa-math-opts.c (gimple_expand_builtin_pow): New.
> ? ? ? ?(execute_cse_sincos): Add switch case for BUILT_IN_POW.
>
> Index: gcc/tree-ssa-math-opts.c
> ===================================================================
> --- gcc/tree-ssa-math-opts.c ? ?(revision 174129)
> +++ gcc/tree-ssa-math-opts.c ? ?(working copy)
> @@ -1024,6 +1024,39 @@ gimple_expand_builtin_powi (gimple_stmt_iterator *
> ? return NULL_TREE;
> ?}
>
> +/* ARG0 and ARG1 are the two arguments to a pow builtin call in GSI
> + ? with location info LOC. ?If possible, create an equivalent and
> + ? less expensive sequence of statements prior to GSI, and return an
> + ? expession holding the result. ?*/
> +
> +static tree
> +gimple_expand_builtin_pow (gimple_stmt_iterator *gsi, location_t loc,
> + ? ? ? ? ? ? ? ? ? ? ? ? ?tree arg0, tree arg1)
> +{
> + ?REAL_VALUE_TYPE c, cint;
> + ?HOST_WIDE_INT n;
> +
> + ?/* If the exponent isn't a constant, there's nothing of interest
> + ? ? to be done. ?*/
> + ?if (TREE_CODE (arg1) != REAL_CST)
> + ? ?return NULL_TREE;
> +
> + ?/* If the exponent is equivalent to an integer, expand it into
> + ? ? multiplies when profitable. ?*/
> + ?c = TREE_REAL_CST (arg1);
> + ?n = real_to_integer (&c);
> + ?real_from_integer (&cint, VOIDmode, n, n < 0 ? -1 : 0, 0);
> +
> + ?if (real_identical (&c, &cint)
> + ? ? ?&& ((n >= -1 && n <= 2)
> + ? ? ? ? || (flag_unsafe_math_optimizations
> + ? ? ? ? ? ? && optimize_insn_for_speed_p ()
> + ? ? ? ? ? ? && powi_cost (n) <= POWI_MAX_MULTS)))
> + ? ?return gimple_expand_builtin_powi (gsi, loc, arg0, n);
> +
> + ?return NULL_TREE;
> +}
> +
> ?/* Go through all calls to sin, cos and cexpi and call execute_cse_sincos_1
> ? ?on the SSA_NAME argument of each of them. ?Also expand powi(x,n) into
> ? ?an optimal number of multiplies, when n is a constant. ?*/
> @@ -1065,6 +1098,23 @@ execute_cse_sincos (void)
> ? ? ? ? ? ? ? ? ? ?cfg_changed |= execute_cse_sincos_1 (arg);
> ? ? ? ? ? ? ? ? ?break;
>
> + ? ? ? ? ? ? ? CASE_FLT_FN (BUILT_IN_POW):
> + ? ? ? ? ? ? ? ? arg0 = gimple_call_arg (stmt, 0);
> + ? ? ? ? ? ? ? ? arg1 = gimple_call_arg (stmt, 1);
> +
> + ? ? ? ? ? ? ? ? loc = gimple_location (stmt);
> + ? ? ? ? ? ? ? ? result = gimple_expand_builtin_pow (&gsi, loc, arg0, arg1);
> +
> + ? ? ? ? ? ? ? ? if (result)
> + ? ? ? ? ? ? ? ? ? {
> + ? ? ? ? ? ? ? ? ? ? tree lhs = gimple_get_lhs (stmt);
> + ? ? ? ? ? ? ? ? ? ? gimple new_stmt = gimple_build_assign (lhs, result);
> + ? ? ? ? ? ? ? ? ? ? gimple_set_location (new_stmt, loc);
> + ? ? ? ? ? ? ? ? ? ? unlink_stmt_vdef (stmt);
> + ? ? ? ? ? ? ? ? ? ? gsi_replace (&gsi, new_stmt, true);
> + ? ? ? ? ? ? ? ? ? }
> + ? ? ? ? ? ? ? ? break;
> +
> ? ? ? ? ? ? ? ?CASE_FLT_FN (BUILT_IN_POWI):
> ? ? ? ? ? ? ? ? ?arg0 = gimple_call_arg (stmt, 0);
> ? ? ? ? ? ? ? ? ?arg1 = gimple_call_arg (stmt, 1);
>
>
>