[11u] RFR 8255550: x86: Assembler::cmpq(Address dst, Register src) encoding is incorrect

[Hohensee, Paul]

Lgtm.

Thanks
Paul

On 11/12/20, 7:25 AM, "jdk-updates-dev on behalf of Aleksey Shipilev" <jdk-updates-dev-retn at openjdk.java.net on behalf of shade at redhat.com> wrote:

    Original bug:
       https://bugs.openjdk.java.net/browse/JDK-8255550
       https://git.openjdk.java.net/jdk/commit/9e5bbff5

    Backporting this for parity in 11u. The code shape is a bit different due to clean ups in later JDK.
    11u patch is:

    diff -r 36e0ac0a01ad src/hotspot/cpu/x86/assembler_x86.cpp
    --- a/src/hotspot/cpu/x86/assembler_x86.cpp     Wed May 20 11:29:11 2020 -0700
    +++ b/src/hotspot/cpu/x86/assembler_x86.cpp     Thu Nov 12 15:47:56 2020 +0100
    @@ -8588,7 +8588,7 @@
      void Assembler::cmpq(Address dst, Register src) {
        InstructionMark im(this);
        prefixq(dst, src);
    -  emit_int8(0x3B);
    +  emit_int8(0x39);
        emit_operand(src, dst);
      }

    Testing: checking code usages (none!), tier1

    --
    Thanks,
    -Aleksey