On Tue, May 24, 2011 at 10:35 PM, William J. Schmidt
<wschm...@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 <wschm...@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);
>
>
>
