Hi, is there a plan to support -mrecip=rsqrt for Aarch64?
Regards, Venkat. > -----Original Message----- > From: gcc-patches-ow...@gcc.gnu.org [mailto:gcc-patches- > ow...@gcc.gnu.org] On Behalf Of Benedikt Huber > Sent: Thursday, June 18, 2015 5:34 PM > To: gcc-patches@gcc.gnu.org > Cc: benedikt.hu...@theobroma-systems.com; > philipp.toms...@theobroma-systems.com > Subject: [PATCH] [aarch64] Implemented reciprocal square root (rsqrt) > estimation in -ffast-math > > arch64 offers the instructions frsqrte and frsqrts, for rsqrt estimation and a > Newton-Raphson step, respectively. > There are ARMv8 implementations where this is faster than using fdiv and > rsqrt. > It runs three steps for double and two steps for float to achieve the needed > precision. > > There is one caveat and open question. > Since -ffast-math enables flush to zero intermediate values between > approximation steps will be flushed to zero if they are denormal. > E.g. This happens in the case of rsqrt (DBL_MAX) and rsqrtf (FLT_MAX). > The test cases pass, but it is unclear to me whether this is expected behavior > with -ffast-math. > > The patch applies to commit: > svn+ssh://gcc.gnu.org/svn/gcc/trunk@224470 > > Please consider including this patch. > Thank you and best regards, > Benedikt Huber > > Benedikt Huber (1): > 2015-06-15 Benedikt Huber <benedikt.hu...@theobroma-systems.com> > > gcc/ChangeLog | 9 +++ > gcc/config/aarch64/aarch64-builtins.c | 60 ++++++++++++++++ > gcc/config/aarch64/aarch64-protos.h | 2 + > gcc/config/aarch64/aarch64-simd.md | 27 ++++++++ > gcc/config/aarch64/aarch64.c | 63 +++++++++++++++++ > gcc/config/aarch64/aarch64.md | 3 + > gcc/testsuite/gcc.target/aarch64/rsqrt.c | 113 > +++++++++++++++++++++++++++++++ > 7 files changed, 277 insertions(+) > create mode 100644 gcc/testsuite/gcc.target/aarch64/rsqrt.c > > -- > 1.9.1
