PS The benefit of an intrinsic in a case like this is being to use a
platform-optimized implementation, trading off native instruction,
floating-point branch, and bitwise conversion costs.
-Joe
On 7/8/2021 4:26 AM, Joe Darcy wrote:
On 7/8/2021 3:50 AM, Andrew Haley wrote:
On Thu, 8 Jul 2021 09:43:35 GMT, Andrew Haley <a...@openjdk.org> wrote:
Moves between GPRs and FPRs are often slow. There's a 10-cycle
latency on some AArch64, so we avoid it whenever we can. Mind you,
we don't care about this patch because we always generate FABS from
an intrinsic anyway.
For avoidance of doubt, that's the round-trip latency.
-------------
PR: https://git.openjdk.java.net/jdk/pull/4711
For coding this functionality in Java, the natural way to do this uses
either an if statement or the bit-wise conversion, which usually
implies GPRs to/from FPRs movement. I don't see a way to avoid both an
if statement and bitwise conversion.
-Joe
