------- Comment #48 from rguenth at gcc dot gnu dot org 2010-03-19 10:35
-------
Untested patch doing 2):
Index: builtins.c
===================================================================
--- builtins.c (revision 157561)
+++ builtins.c (working copy)
@@ -2980,10 +2980,16 @@ expand_builtin_pow (tree exp, rtx target
&& ((flag_unsafe_math_optimizations
&& optimize_insn_for_speed_p ()
&& powi_cost (n/2) <= POWI_MAX_MULTS)
- /* Even the c==0.5 case cannot be done unconditionally
+ /* Even the c == 0.5 case cannot be done unconditionally
when we need to preserve signed zeros, as
pow (-0, 0.5) is +0, while sqrt(-0) is -0. */
- || (!HONOR_SIGNED_ZEROS (mode) && n == 1)))
+ || (!HONOR_SIGNED_ZEROS (mode) && n == 1)
+ /* For c == 1.5 we can assume that x * sqrt (x) is always
+ smaller than pow (x, 1.5) if sqrt will not be expanded
+ as a call. */
+ || (n == 2
+ && (optab_handler (sqrt_optab, mode)->insn_code
+ != CODE_FOR_nothing))))
{
tree call_expr = build_call_nofold (fn, 1, narg0);
/* Use expand_expr in case the newly built call expression
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40106
