On Mon, Jun 12, 2017 at 07:56:54AM +0000, Tamar Christina wrote: > Hi All, > > this patch implements a optimization rewriting > > x * copysign (1.0, y) and > x * copysign (-1.0, y) > > to: > > x ^ (y & (1 << sign_bit_position)) > > This is done by creating a special builtin during matching and generate the > appropriate instructions during expand. This new builtin is called XORSIGN. > > The expansion of xorsign depends on if the backend has an appropriate optab > available. If this is not the case then we use a modified version of the > existing > copysign which does not take the abs value of the first argument as a fall > back. > > This patch is a revival of a previous patch > https://gcc.gnu.org/ml/gcc-patches/2015-10/msg00069.html > > Bootstrapped on both aarch64-none-linux-gnu and x86_64 with no issues. > Regression done on aarch64-none-linux-gnu and no regressions. > > Ok for trunk?
Please only enable this if you have XORSIGN and XORSIGNF. On the PowerPC this would involve moving the value from the vector/floating point registers to the general purpose registers to do the XOR operation and then back to the vector/floating point registers. Note, the PowerPC has an instruction that does copysign directly. It would be better just to do the copysign/multiply. -- Michael Meissner, IBM IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA email: meiss...@linux.vnet.ibm.com, phone: +1 (978) 899-4797
