JDK-8233081 : C1: PatchingStub for field access copies too much
  • Type: Bug
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 11,14
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2019-10-28
  • Updated: 2021-01-27
  • Resolved: 2019-11-05
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JDK 11 JDK 13 JDK 14
11.0.6Fixed 13.0.4Fixed 14 b22Fixed
Related Reports
Relates :  
JDK-8234645 - ARM32: C1: PatchingStub for field access: not enough bytes
Relates :  
JDK-8260502 - [s390] NativeMovRegMem::verify() fails because it's too strict
Relates :  
JDK-8231757 - [ppc] Fix VerifyOops. Errors show since 8231058.
Description
C1's PatchingStub copies bytes from the method's regular code area to a dedicated patching template which gets copied back when the patching work is completed.
Currently, C1's PatchingStub with PatchID "access_field_id" copies all bytes between the PatchingStub's instanciation and the patching_epilog call.
This is not only more than necessary, it can cause _bytes_to_copy to exceed its one byte limitation: emit_int8(_bytes_to_copy).
On some platforms, code for VerifyOops is part of the code which gets copied forth and back. This is unnecessary and should be avoided.
Note that the template for PatchID "access_field_id" never gets executed, so there's no reason for copying more than the code to be patched.

So there are basically 2 issues:
- Possible size overflow (depending on platform and activated features)
- Wasted code cache space
Comments
Fix request jdk13u Applies cleanly.
29-05-2020
Fix request jdk11u Already backported to 11.0.7-oracle. We should have it in open 11u, too. Applies cleanly.
20-11-2019
URL: https://hg.openjdk.java.net/jdk/jdk/rev/8623f75be895 User: mdoerr Date: 2019-11-05 10:54:18 +0000
05-11-2019
ILW = C1 patching may overflow and/or waste code cache space, when patching field access but never showed up, no workaround = MLH = P4
29-10-2019