On Mon, 14 Feb 2022 17:14:10 GMT, Jatin Bhateja <jbhat...@openjdk.org> wrote:
>> That pseudocode would make a very useful comment too. This whole patch is >> very thinly commented. > >> > Hi, IIRC for evex encoding you can embed the RC control bit directly in >> > the evex prefix, removing the need to rely on global MXCSR register. >> > Thanks. >> >> Hi @merykitty , You are correct, we can embed RC mode in instruction >> encoding of round instruction (towards -inf,+inf, zero). But to match the >> semantics of Math.round API one needs to add 0.5[f] to input value and then >> perform rounding over resultant value, which is why @sviswa7 suggested to >> use a global rounding mode driven by MXCSR.RC so that intermediate floating >> inexact values are resolved as desired, but OOO execution may misplace >> LDMXCSR and hence may have undesired side effects. > > **Just want to correct above statement, LDMXCSR will not be > re-ordered/re-scheduled early OOO backend.** > That pseudocode would make a very useful comment too. This whole patch is > very thinly commented. I have replaced earlier bulky sequence, new sequence is having similar performance but reduction in code may improve inlining behavior. Added descriptive comments around the special cases. ------------- PR: https://git.openjdk.java.net/jdk/pull/7094
