RFR: 8260355: AArch64: deoptimization stub should save vector registers [v3]

[Nick Gasson]

> This is an AArch64 port of the fix for JDK-8256056 "Deoptimization stub
> doesn't save vector registers on x86". The problem is that a vector
> produced by the Vector API may be stored in a register when the deopt
> blob is called. Because the deopt blob only stores the lower half of
> vector registers, the full vector object cannot be rematerialized during
> deoptimization. So the following will crash on AArch64 with current JDK:
> 
>   make test TEST="jdk/incubator/vector" \
>     JTREG="VM_OPTIONS=-XX:+DeoptimizeALot -XX:DeoptimizeALotInterval=0"
> 
> The fix is to store the full vector registers by passing
> save_vectors=true to save_live_registers() in the deopt blob. Because
> save_live_registers() places the integer registers above the floating
> registers in the stack frame, RegisterSaver::r0_offset_in_bytes() needs
> to calculate the SP offset based on whether full vectors were saved, and
> whether those vectors were NEON or SVE, rather than using a static
> offset as it does currently.
> 
> The change to VectorSupport::allocate_vector_payload_helper() is
> required because we only store the lowest VMReg slot in the oop map.
> However unlike x86 the vector registers are always saved in a contiguous
> region of memory, so we can calculate the address of each vector element
> as an offset from the address of the first slot. X86 handles this in
> RegisterMap::pd_location() but that won't work on AArch64 because with
> SVE there isn't a unique VMReg corresponding to each four-byte physical
> slot in the vector (there are always exactly eight logical VMRegs
> regardless of the actual vector length).
> 
> Tested hotspot_all_no_apps and jdk_core.

Nick Gasson has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Merge branch 'master' into 8260355
 - Move SVE slot handling to RegisterMap::pd_location
 - 8260355: AArch64: deoptimization stub should save vector registers
   
   This is an AArch64 port of the fix for JDK-8256056 "Deoptimization stub
   doesn't save vector registers on x86". The problem is that a vector
   produced by the Vector API may be stored in a register when the deopt
   blob is called. Because the deopt blob only stores the lower half of
   vector registers, the full vector object cannot be rematerialized during
   deoptimization. So the following will crash on AArch64 with current JDK:
   
     make test TEST="jdk/incubator/vector" \
       JTREG="VM_OPTIONS=-XX:+DeoptimizeALot -XX:DeoptimizeALotInterval=0"
   
   The fix is to store the full vector registers by passing
   save_vectors=true to save_live_registers() in the deopt blob. Because
   save_live_registers() places the integer registers above the floating
   registers in the stack frame, RegisterSaver::r0_offset_in_bytes() needs
   to calculate the SP offset based on whether full vectors were saved, and
   whether those vectors were NEON or SVE, rather than using a static
   offset as it does currently.
   
   The change to VectorSupport::allocate_vector_payload_helper() is
   required because we only store the lowest VMReg slot in the oop map.
   However unlike x86 the vector registers are always saved in a contiguous
   region of memory, so we can calculate the address of each vector element
   as an offset from the address of the first slot. X86 handles this in
   RegisterMap::pd_location() but that won't work on AArch64 because with
   SVE there isn't a unique VMReg corresponding to each four-byte physical
   slot in the vector (there are always exactly eight logical VMRegs
   regardless of the actual vector length).
   
   Tested hotspot_all_no_apps and jdk_core.

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2279/files
  - new: https://git.openjdk.java.net/jdk/pull/2279/files/2364f3dd..498310d4

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2279&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2279&range=01-02

  Stats: 16985 lines in 325 files changed: 3685 ins; 4804 del; 8496 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2279.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2279/head:pull/2279

PR: https://git.openjdk.java.net/jdk/pull/2279