[aarch64-port-dev ] RFR: JDK-8143584 Aarch64: Load constant pool tag and class status with load acquire

[Hui Shi]

Hi,

Could someone help review and sponsor more runtime fix for aarch64?
bug: https://bugs.openjdk.java.net/browse/JDK-8143584
webrev: http://cr.openjdk.java.net/~hshi/8143584/webrev/

This also fix some random crash in template interpreter. One of the crash
test is langtools/test/tools/javac/TestLambdaToMethodStats.java. The
symptom is: in checkcast, klass being checked is not valid klass pointer
and trigger segmentation fault. The root cause is on aarch64 it miss load
acquire when trying to read tag in constant pool before load resolved
klass. Resolved class load might finish before tag load.

Code for checkcast before fix
   0x7f8409a5a0: add x8, x3, #0x4
   0x7f8409a5a4: ldrb w1, [x8,x19] // load tag
   0x7f8409a5a8: cmp x1, #0x7 __ cmp(r1, JVM_CONSTANT_Class);

   0x7f8409a62c: mov x3, x0
   0x7f8409a630: add x0, x2, x19, uxtx #3
   0x7f8409a634: ldr x0, [x0,#80]
   0x7f8409a638: ldr w19, [x3,#8] // load resolved class
   0x7f8409a63c: eor x19, x19, #0x800000000 // x19 hold klass being checked


Load resolved class might finish before load tag and read incorrect value.
Fix is using load acquire when load tag.
These tags are updated with release store in
ConstantPool::release_tag_at_put (which uses OrderAccess::release_store),
tags need be loaded with load acquire instruction ensure later resolved
class load get correct klass. Fix is using load acquire when load tag and
compare.

After fix:
  0x0000007f8009a6a4: add x8, x8, x19
  0x0000007f8009a6a8: ldarb w1, [x8]
  0x0000007f8009a6ac: cmp x1, #0x7
  0x0000007f8009a6b0: b.eq 0x0000007f8009a730
  ….

  0x0000007f8009a730: mov x3, x0
  0x0000007f8009a734: add x0, x2, x19, uxtx #3
  0x0000007f8009a738: ldr x0, [x0,#80]
  0x0000007f8009a73c: ldr w19, [x3,#8]
  0x0000007f8009a740: eor x19, x19, #0x800000000

Checking similar places for aarch64 runtime, more places needs similar fix:
1. Instanceof is similar with checkcast
2. "ldc", similar with load resolved class in checkcast, need load acquire
when loading tag in constant pool
3. "new" loads tag for resolved class.
4. "new" Loads and checks class initialized status, class init status
update is guarded with orderaccess::storestore, need guarantee order
between load class initialize status and load "instance_size in
InstanceKlass".
5. C1 runtime checks if class initialize status when generate code for
fast_new_instance_init_check_id, similar with "new".

Regards
Shi Hui