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  1. JDK
  2. JDK-8255628

AOT code fails with mismatched UseEmptySlotsInSupers

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: P3
    • Resolution: Not an Issue
    • Affects Version/s: 16
    • Fix Version/s: tbd
    • Component/s: hotspot

      Description

      The AOT library must be built with the same UseEmptySlotsInSupers value as used at runtime, since AOT assumes that all field offsets are the same as at runtime. When a mismatched UseEmptySlotsInSupers is specified, AOT code can fail.

      Here's a simple reproducer that fails with a fastdebug build from a recent openjdk repo:

      ==========================================================================================
      # doit.sh
      # Please edit the following two lines
      export JAVA_HOME=/jdk/bld/fastdebug/images/jdk
      export DEVKIT=/home/iklam/devkit/latest

      # Gather the list of classes to compile
      ${JAVA_HOME}/bin/java -Xshare:off -verbose -version 2> /dev/null | grep class.load.*jrt..java.base \
          | sed -e 's/.*class,load..//g' -e 's/ source.*//g' > classes.txt

      # This takes about 160 seconds on a fast machine
      if test ! -f test.so; then
          time ${JAVA_HOME}/bin/jaotc \
              --info \
              -J-Xmx4g \
              -J-server \
              -J-ea \
              -J-esa \
              --compile-commands open/test/hotspot/jtreg/compiler/aot/scripts/java.base-list.txt \
              --linker-path ${DEVKIT}/bin/ld \
              --compile-with-assertions \
              --output \
              test.so \
              --class-name $(cat classes.txt) | tee test.so.log
      fi

      echo "=== running with +UseEmptySlotsInSupers (OK)"
      ${JAVA_HOME}/bin/java -Xshare:off -ea -esa -XX:+UnlockExperimentalVMOptions -XX:AOTLibrary=$(pwd)/test.so -XX:+UseEmptySlotsInSupers -version

      echo "=== running with -UseEmptySlotsInSupers (will get stuck)"
      ${JAVA_HOME}/bin/java -Xshare:off -ea -esa -XX:+UnlockExperimentalVMOptions -XX:AOTLibrary=$(pwd)/test.so -XX:-UseEmptySlotsInSupers -version
      ==========================================================================================

      $ bash doit.sh
      === running with +UseEmptySlotsInSupers (OK)
      java version "16-internal" 2021-03-16
      Java(TM) SE Runtime Environment (fastdebug build 16-internal+0-adhoc.iklam.open)
      Java HotSpot(TM) 64-Bit Server VM (fastdebug build 16-internal+0-adhoc.iklam.open, mixed mode, aot)
      === running with -UseEmptySlotsInSupers (will get stuck)
      ^C

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            Assignee:
            Unassigned Unassigned
            Reporter:
            iklam Ioi Lam
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              Created:
              Updated:
              Resolved: