JDK-8234160 : Enable optimized mitigation for Intel jcc erratum in C2
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 8,11,14
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • CPU: x86_64
  • Submitted: 2019-11-14
  • Updated: 2021-10-18
  • Resolved: 2020-02-24
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JDK 15
15 b12Fixed
Related Reports
Relates :  
JDK-8240370 - Provide Intel JCC Erratum opt-out
Relates :  
JDK-8240610 - [JVMCI] Export VMVersion::_has_intel_jcc_erratum to JVMCI compiler
Relates :  
JDK-8241438 - Move IntelJccErratum mitigation code to platform-specific code
Relates :  
JDK-8274325 - C4819 warning at vm_version_x86.cpp on Windows after JDK-8234160
Relates :  
JDK-8249165 - Remove unneeded nops introduced by 8234160 changes
Description
Intel released an erratum about conditional branches crossing 32 bit boundaries. It is described here:

https://www.intel.com/content/dam/support/us/en/documents/processors/mitigations-jump-conditional-code-erratum.pdf

It seems like microcode updates will prevent such branches from being cached, and sensitive branches might want to be aligned properly. So in ZGC we should align our fast path check.

We should also sort out the mach IR of C2 to be reasonably well aligned.
Comments
I am removing jdk11-graalvm label because JDK-8244147 resolved issue for Graal.
26-05-2020
Candidate 11u backport: https://cr.openjdk.java.net/~shade/8234160/webrev.11u.01/ -- passes tier{1,2,3} on my affected SKL-X.
09-03-2020
URL: https://hg.openjdk.java.net/jdk/jdk/rev/fe2befa06c39 User: eosterlund Date: 2020-02-24 15:28:22 +0000
24-02-2020
Is there any update to this issue? I am waiting for the bool VM_Version::compute_has_intel_jcc_erratum() helper method to be merged.
15-01-2020