JDK-8309978 : [x64] Fix useless padding
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 17,21,22
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • OS: generic
  • CPU: x86
  • Submitted: 2023-06-13
  • Updated: 2023-07-12
  • Resolved: 2023-06-15
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JDK 22
22 b03Fixed
Description
Due to typo in IntelJccErratum::compute_padding() useless padding could be generated:

030     B2: #   out( B4 B3 ) <- in( B1 )  Freq: 0.999999
        nop     # 16 bytes pad for loops and calls
040     cmpb    [R12 + R10 << 3 + #144] (compressed oop addressing), #42
049     jle,s   B4  P=0.667944 C=6785.000000
Comments
Changeset: 0038491a Author: Vladimir Kozlov <kvn@openjdk.org> Date: 2023-06-15 15:32:45 +0000 URL: https://git.openjdk.org/jdk/commit/0038491abda51b8bd39fabed53624c10abcfe077
15-06-2023
A pull request was submitted for review. URL: https://git.openjdk.org/jdk/pull/14461 Date: 2023-06-14 04:42:22 +0000
14-06-2023
IR framework Phase "Final Code" output before fix: BB#002: 38 Region === 38 24 [[ 38 22 23 ]] 53 Nop === [[ ]] [5200000000053] RFLAGS 23 compB_mem_imm === 38 14 12 [[ 22 ]] #144/0x0000000000000090#42/0x0000002a 22 jmpCon_short === 38 23 [[ 25 21 ]] P=0.667907, C=5375.000000 !jvms: TestPadding::test @ bci:10 (line 57)
14-06-2023