On Wed, 4 May 2022 23:27:45 GMT, Vladimir Kozlov <[email protected]> wrote:
>> The changes to `Float` and `Double` look good. I don't think we need
>> additional tests, see test/jdk/java/lang/Math/IeeeRecommendedTests.java.
>>
>> At first i thought we no longer need PR #8459 but it seems both PRs are
>> complimentary, albeit PR #8459 has more modest performance gains for the
>> intrinsics.
>
>> The changes to `Float` and `Double` look good. I don't think we need
>> additional tests, see test/jdk/java/lang/Math/IeeeRecommendedTests.java.
>
> Thank you, Paul for pointing the test. It means we need to run tier4 (which
> runs these tests with -Xcomp) to make sure methods are compiled by C2.
@vnkozlov I have added comments to describe the changes in `cmpOpUCF` and the
reasons behind the `cmov_regUCF2_eq` match rules. Using `expand` broke the
build with `Syntax Error: :For expand in cmovI_regUCF2_eq to work, parameter
declaration order in cmovI_regUCF2_ne must follow matchrule`.
@sviswa7 (x != y) ? a : b can be calculated using pseudocode as follow:
res = (!ZF || PF) ? a : b
= !ZF ? a : (PF ? a : b)
which can be calculated using
cmovp rb, ra // rb1 = PF ? ra : rb
cmovne rb, ra // rb2 = !ZF ? ra : rb1 = !ZF ? ra : (PF ? ra : rb)
Furthermore, since `(x == y) == !(x != y)`, we have `((x == y) ? a : b) == ((x
!= y) ? b : a)`, which explains the implementation of `cmov_regUCF2_eq`.
@vamsi-parasa Thanks a lot for your suggestion, I have modified the PR
description as you say.
-------------
PR: https://git.openjdk.java.net/jdk/pull/8525
