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.
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);
