We wrongly treat the meet of two constant TypeAryPtr with different nullness as exact. This is wrong and triggers an assert during CCP.


Original report:

The following two tests fail in tier1 with -Xcomp with the assertion below:

- valhalla/valuetypes/NullRestrictedArraysTest.java
- valhalla/valuetypes/FlatVarHandleTest.java

Could be related to JDK-8351569.

Output:
   0 Root === 0 38 66 77 88 99 653 237 662 403 631 644 [[ 0 1 3 24 25 33 40 56 61 72 83 94 156 398 161 382 381 183 189 193 200 221 232 272 301 305 336 335 310 311 314 430 415 479 417 ]]
 538 Phi === 536 24 496 [[ 493 496 585 500 506 526 526 526 537 ]] #int:0..max-1:www #tripcount !orig=108,[299] !jvms: NullRestrictedArraysTest::testVarHandleArray @ bci:10 (line 184)
  11 Parm === 3 [[ 39 26 ]] Parm1: narrowoop: java/lang/Object *[int:>=0] (java/lang/Cloneable,java/io/Serializable) * !jvms: NullRestrictedArraysTest::testVarHandleArray @ bci:-1 (line 183)
  31 IfTrue === 30 [[ 50 39 ]] #1 !jvms: NullRestrictedArraysTest::testVarHandleArray @ bci:6 (line 183)
 490 If === 483 287 [[ 491 492 ]] P=0.500000, C=-1.000000
 301 ConI === 0 [[ 514 ]] #int:3
 537 ConvI2L === _ 538 [[ 512 514 518 ]] #long:0..maxint-1:www !orig=316,[192] !jvms: NullRestrictedArraysTest::testVarHandleArray @ bci:22 (line 184)
  39 CastPP === 31 11 [[ 664 41 41 399 62 73 84 95 286 196 233 428 233 223 223 197 195 196 197 572 526 526 ]] #narrowoop: java/lang/Object *[int:>=0] (java/lang/Cloneable,java/io/Serializable):NotNull * !jvms: NullRestrictedArraysTest::testVarHandleArray @ bci:6 (line 183)
 492 IfFalse === 490 [[ 659 636 664 ]] #0
 514 LShiftL === _ 537 301 [[ 513 ]] !orig=302 !jvms: NullRestrictedArraysTest::testVarHandleArray @ bci:22 (line 184)
 664 CheckCastPP === 492 39 [[ 513 509 549 528 513 ]] #flat:narrowoop: NullRestrictedArraysTest$Value (NullRestrictedArraysTest$I):exact *[int:>=0] (java/lang/Cloneable,java/io/Serializable):NotNull:exact:flat(+bot) * !orig=[297],[431] !jvms: NullRestrictedArraysTest::testVarHandleArray @ bci:22 (line 184)
 513 AddP === _ 664 664 514 [[ 509 ]] !orig=304 !jvms: NullRestrictedArraysTest::testVarHandleArray @ bci:22 (line 184)
told = flat:narrowoop: NullRestrictedArraysTest$Value (NullRestrictedArraysTest$I):exact *[int:>=0] (java/lang/Cloneable,java/io/Serializable):NotNull:exact:flat(+bot) *
tnew = flat:narrowoop: NullRestrictedArraysTest$Value (NullRestrictedArraysTest$I):exact *[int:>=0] (java/lang/Cloneable,java/io/Serializable):NotNull:exact:flat(+bot)+any * [narrow]

Failure:
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/opt/mach5/mesos/work_dir/slaves/d14b0f60-a475-4b75-84a6-b4452f3162de-S13935/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/06d09a65-a3f6-417f-bb9d-c3e30b8809a7/runs/c7475573-26c7-464a-821c-e18f0ef2ce5f/workspace/open/src/hotspot/share/opto/phaseX.cpp:1840), pid=1380342, tid=1380358
# fatal error: Not monotonic
#
# JRE version: Java(TM) SE Runtime Environment (25.0) (fastdebug build 25-lworld5ea-LTS-2025-03-27-1423593.christian.hagedorn.valhalla2)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 25-lworld5ea-LTS-2025-03-27-1423593.christian.hagedorn.valhalla2, compiled mode, tiered, compressed oops, compressed class ptrs, g1 gc, linux-amd64)
# Problematic frame:
# V [libjvm.so+0x17481f9] PhaseCCP::verify_type(Node*, Type const*, Type const*)+0x169

C2:96010 18126 b 4 FlatVarHandleTest$WeakPoint::makePoints (43 bytes)

Stack: [0x00007f56e0560000,0x00007f56e0660000], sp=0x00007f56e065b060, free space=1004k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x17481f9] PhaseCCP::verify_type(Node*, Type const*, Type const*)+0x169 (phaseX.cpp:1840)
V [libjvm.so+0x174d147] PhaseCCP::analyze()+0x417 (phaseX.cpp:1883)
V [libjvm.so+0xac9fa6] Compile::Optimize()+0x946 (compile.cpp:2878)
V [libjvm.so+0xacd28b] Compile::Compile(ciEnv*, ciMethod*, int, Options, DirectiveSet*)+0x1f2b (compile.cpp:866)
V [libjvm.so+0x8f75ad] C2Compiler::compile_method(ciEnv*, ciMethod*, int, bool, DirectiveSet*)+0x46d (c2compiler.cpp:142)
V [libjvm.so+0xadab8c] CompileBroker::invoke_compiler_on_method(CompileTask*)+0xbfc (compileBroker.cpp:2331)
V [libjvm.so+0xadbac8] CompileBroker::compiler_thread_loop()+0x598 (compileBroker.cpp:1975)
V [libjvm.so+0x101c47f] JavaThread::thread_main_inner()+0x12f (javaThread.cpp:777)
V [libjvm.so+0x1a28e46] Thread::call_run()+0xb6 (thread.cpp:231)
V [libjvm.so+0x16b8378] thread_native_entry(Thread*)+0x128 (os_linux.cpp:877)