RFR: 8291106: ZPlatformGranuleSizeShift is redundant due to it can not be modified

[Leslie Zhai]

Hi @stefank 

When I am tunning `ZPageSizeSmall` to 16 MB from 2MB:


const size_t ZPlatformGranuleSizeShift          = 24; // 16MB

// Granule shift/size
const size_t      ZGranuleSizeShift             = ZPlatformGranuleSizeShift;

// Page size shifts
const size_t      ZPageSizeSmallShift           = ZGranuleSizeShift;

// Page sizes
const size_t      ZPageSizeSmall                = (size_t)1 << ZPageSizeSmallShift;


`zBitField` failed to work:


Internal Error
 (/home/zhaixiang/jdk/src/hotspot/share/gc/z/zBitField.hpp:76), pid=923047, tid=923069
#  assert(((ContainerType)value & (FieldMask << ValueShift)) == (ContainerType)value) failed: Invalid value
#
# JRE version: OpenJDK Runtime Environment (20.0) (fastdebug build 20-internal-adhoc.root.jdk)
# Java VM: OpenJDK 64-Bit Server VM (fastdebug 20-internal-adhoc.root.jdk, mixed mode, sharing, tiered, compressed class ptrs, z gc, linux-aarch64)


Perhaps `mask` also need to be adjusted:


static size_t object_index(oop obj) {
  const uintptr_t addr = ZOop::to_address(obj);
  const uintptr_t offset = ZAddress::offset(addr);
  const uintptr_t mask = ZGranuleSize - 1;
  return (offset & mask) >> ZObjectAlignmentSmallShift;
}


Back to the point: ZPlatformGranuleSizeShift is redundant due to it can not be modified, for example, `24`, so I removed the `ZPlatformGranuleSizeShift` from cpu backends, just keep it for debugging AArch64 to see the issue.

Please review my patch.

Thanks,
Leslie Zhai

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

Commit messages:
 - 8291106: ZPlatformGranuleSizeShift is redundant due to it can not be modified
 - ZPlatformGranuleSizeShift is redundant due to it can not be modified

Changes: https://git.openjdk.org/jdk/pull/9582/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9582&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8291106
  Stats: 20 lines in 6 files changed: 15 ins; 3 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/9582.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9582/head:pull/9582

PR: https://git.openjdk.org/jdk/pull/9582