Re: RFR: JDK-8239794 Move -Os from JVM feature 'minimal' to new feature 'opt-size'
Hi Magnus, This seems reasonable to me. The definition of OPT_SPEED_SRC is likely out of date, but we have no data for modifying that list. People who try opt-size will likely try to refine it. Thanks, David - On 22/02/2020 2:13 am, Magnus Ihse Bursie wrote: Prior to JDK-8239450, it was possible to explicitly set the JVM feature 'minimal', even when building variant server. The reason for doing this was to get the code in JvmFeatures.gmk that sets JVM_OPTIMIZATION := SIZE (except for a handful of files). Since this functionality is important in itself (and it has been requested by users in the community), it should be controlled by a separate feature, instead of just as a part of the 'minimal' feature, which signals that the minimal JVM variant is being built. However, when looking into it, I noticed several aspects of the old code that I wanted to address. First of all, the old code had the size optimization silently ignored, if also 'link-time-opt' was enabled. This does not make any sense, since it is completely possible to do both. This code was written in the new Hotspot build system as a way to mimick the old Hotspot build system. I'm guessing that this was initially introduced as a way to enable the size optimization when building minimal, except for arm-32 systems, which were the only system to have link-time-opt enabled. After some head scratching, I implemented the logic in the following way: * If opt-size is enabled, the JVM_OPTIMIZATION := SIZE is always performed, regardless of any other features. * And contrary, link-time-opt can be enabled/disabled independent on opt-size * When building minimal on arm-32, opt-size is not enabled by default, but link-time-opt is (as it was before) * When building minimal on any other platform, opt-size is enabled by default, but link-time-opt is not (as it was before) * When building any other variant, opt-size is disabled by default This makes standard builds of minimal with no extra features enabled/disabled behave the same as before, while giving the maximum of flexibility to change this. But I'd like to get input from someone in the Hotspot team that this is a sound approach. Also, this has apparently never been tested by any other compiler than gcc and/or clang, since we explicitly add the compiler flag -fno-optimize-sibling-calls. I wrapped this in a compiler check. Note that this patch is based on JDK-8239789 (Follow-up on JVM feature rewrite). Bug: https://bugs.openjdk.java.net/browse/JDK-8239794 WebRev: http://cr.openjdk.java.net/~ihse/JDK-8239794-create-opt-size-jvm-feature/webrev.01 /Magnus
Re: RFR: JDK-8239794 Move -Os from JVM feature 'minimal' to new feature 'opt-size'
Looks good to me. /Erik On 2020-02-21 08:13, Magnus Ihse Bursie wrote: Prior to JDK-8239450, it was possible to explicitly set the JVM feature 'minimal', even when building variant server. The reason for doing this was to get the code in JvmFeatures.gmk that sets JVM_OPTIMIZATION := SIZE (except for a handful of files). Since this functionality is important in itself (and it has been requested by users in the community), it should be controlled by a separate feature, instead of just as a part of the 'minimal' feature, which signals that the minimal JVM variant is being built. However, when looking into it, I noticed several aspects of the old code that I wanted to address. First of all, the old code had the size optimization silently ignored, if also 'link-time-opt' was enabled. This does not make any sense, since it is completely possible to do both. This code was written in the new Hotspot build system as a way to mimick the old Hotspot build system. I'm guessing that this was initially introduced as a way to enable the size optimization when building minimal, except for arm-32 systems, which were the only system to have link-time-opt enabled. After some head scratching, I implemented the logic in the following way: * If opt-size is enabled, the JVM_OPTIMIZATION := SIZE is always performed, regardless of any other features. * And contrary, link-time-opt can be enabled/disabled independent on opt-size * When building minimal on arm-32, opt-size is not enabled by default, but link-time-opt is (as it was before) * When building minimal on any other platform, opt-size is enabled by default, but link-time-opt is not (as it was before) * When building any other variant, opt-size is disabled by default This makes standard builds of minimal with no extra features enabled/disabled behave the same as before, while giving the maximum of flexibility to change this. But I'd like to get input from someone in the Hotspot team that this is a sound approach. Also, this has apparently never been tested by any other compiler than gcc and/or clang, since we explicitly add the compiler flag -fno-optimize-sibling-calls. I wrapped this in a compiler check. Note that this patch is based on JDK-8239789 (Follow-up on JVM feature rewrite). Bug: https://bugs.openjdk.java.net/browse/JDK-8239794 WebRev: http://cr.openjdk.java.net/~ihse/JDK-8239794-create-opt-size-jvm-feature/webrev.01 /Magnus
RFR: JDK-8239794 Move -Os from JVM feature 'minimal' to new feature 'opt-size'
Prior to JDK-8239450, it was possible to explicitly set the JVM feature 'minimal', even when building variant server. The reason for doing this was to get the code in JvmFeatures.gmk that sets JVM_OPTIMIZATION := SIZE (except for a handful of files). Since this functionality is important in itself (and it has been requested by users in the community), it should be controlled by a separate feature, instead of just as a part of the 'minimal' feature, which signals that the minimal JVM variant is being built. However, when looking into it, I noticed several aspects of the old code that I wanted to address. First of all, the old code had the size optimization silently ignored, if also 'link-time-opt' was enabled. This does not make any sense, since it is completely possible to do both. This code was written in the new Hotspot build system as a way to mimick the old Hotspot build system. I'm guessing that this was initially introduced as a way to enable the size optimization when building minimal, except for arm-32 systems, which were the only system to have link-time-opt enabled. After some head scratching, I implemented the logic in the following way: * If opt-size is enabled, the JVM_OPTIMIZATION := SIZE is always performed, regardless of any other features. * And contrary, link-time-opt can be enabled/disabled independent on opt-size * When building minimal on arm-32, opt-size is not enabled by default, but link-time-opt is (as it was before) * When building minimal on any other platform, opt-size is enabled by default, but link-time-opt is not (as it was before) * When building any other variant, opt-size is disabled by default This makes standard builds of minimal with no extra features enabled/disabled behave the same as before, while giving the maximum of flexibility to change this. But I'd like to get input from someone in the Hotspot team that this is a sound approach. Also, this has apparently never been tested by any other compiler than gcc and/or clang, since we explicitly add the compiler flag -fno-optimize-sibling-calls. I wrapped this in a compiler check. Note that this patch is based on JDK-8239789 (Follow-up on JVM feature rewrite). Bug: https://bugs.openjdk.java.net/browse/JDK-8239794 WebRev: http://cr.openjdk.java.net/~ihse/JDK-8239794-create-opt-size-jvm-feature/webrev.01 /Magnus
