8346832: runtime/CompressedOops/CompressedCPUSpecificClassSpaceReservation.java fails on RISC-V

[RealFYang]

Hi, please review this small change fixing a test failure.

This test first expects tryReserveForUnscaled and tryReserveForZeroBased from the process output. In addition, when test without CDS, it also expects reserve_between (range [0x0000000800000000-0x0000100000000000) which is not lower than zero-based limit. But the process output gives reserve_between (range [0x0000000100000000-0x0000100000000000), which is not expected.

Previously, we have the code handling this case in CompressedKlassPointers::reserve_address_space_for_compressed_classes.
But I find that the code is gone after JDK-8305895: Implement JEP 450: Compact Object Headers. This is the related change:

diff --git a/src/hotspot/cpu/riscv/compressedKlass_riscv.cpp b/src/hotspot/cpu/riscv/compressedKlass_riscv.cpp
index cffadb4189b..7c8d6b8f5bb 100644
--- a/src/hotspot/cpu/riscv/compressedKlass_riscv.cpp
+++ b/src/hotspot/cpu/riscv/compressedKlass_riscv.cpp
@@ -56,9 +56,9 @@ char* CompressedKlassPointers::reserve_address_space_for_compressed_classes(size
     result = reserve_address_space_for_zerobased_encoding(size, aslr);
   }

-  // Failing that, optimize for case (3) - a base with only bits set between [33-44)
+  // Failing that, optimize for case (3) - a base with only bits set between [32-44)
   if (result == nullptr) {
-    const uintptr_t from = nth_bit(32 + (optimize_for_zero_base ? LogKlassAlignmentInBytes : 0));
+    const uintptr_t from = nth_bit(32);
     constexpr uintptr_t to = nth_bit(44);
     constexpr size_t alignment = nth_bit(32);
     result = reserve_address_space_X(from, to, size, alignment, aslr);

It seems to me more reasonable to add the optimize_for_zero_base check back and replace the LogKlassAlignmentInBytes with
CompressedKlassPointers::max_shift(). max_shift() is used in CompressedKlassPointers::reserve_address_space_for_zerobased_encoding to calculate zerobased_max as well [1].

Testing: same test passes with fastdebug build on linux-riscv64 platform. Tagging @tstuefe

[1] https://github.com/openjdk/jdk/blob/master/src/hotspot/share/oops/compressedKlass.cpp#L201

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Issue

• JDK-8346832: runtime/CompressedOops/CompressedCPUSpecificClassSpaceReservation.java fails on RISC-V (Bug - P4)

Reviewers

• Thomas Stuefe (@tstuefe - Reviewer)
• Feilong Jiang (@feilongjiang - Committer)

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[openjdk]

@RealFYang This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8346832: runtime/CompressedOops/CompressedCPUSpecificClassSpaceReservation.java fails on RISC-V

Reviewed-by: stuefe, fjiang

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At the time when this comment was updated there had been 28 new commits pushed to the master branch:

• 27646e5: 8344148: Add an explicit compiler phase for warning generation
• 8d388cc: 8346457: AOT cache creation crashes with "assert(pair_at(i).match() < pair_at(i+1).match()) failed: unsorted table entries"
• d723597: 8345432: (ch, fs) Replace anonymous Thread with InnocuousThread
• 9c393a2: 8346953: Remove unnecessary @SuppressWarnings annotations (client, Make "can write" check work on Windows #2)
• 9a60f44: 8345668: ZoneOffset.ofTotalSeconds performance regression
• 12700cb: 8346264: "Total compile time" counter should include time spent in failing/bailout compiles
• dd81f8d: 8344079: Minor fixes and cleanups to compiler lint-related code
• ccf3d57: 8346985: Convert test/jdk/com/sun/jdi/ClassUnloadEventTest.java to Class-File API
• 594e519: 8346984: Remove ASM-based benchmarks from Class-File API benchmarks
• c027f2e: 8346983: Remove ASM-based transforms from Class-File API tests
• ... and 18 more: https://git.openjdk.org/jdk/compare/6c59185475eeca83153f085eba27cc0b3acf9bb4...master

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[RealFYang]

/label remove hotspot-compiler

[RealFYang]

/label add hotspot-runtime

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• 01: Full - Incremental (f7070b30)
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[tstuefe]

Hi @RealFYang!

Would not removing the zero-based search be simpler then? We would forfeit the search for an area within 4g-32g then, but if I recall correctly, for bases between 4G and 16TB we use addiw + slli. In other words, we don't take advantage of zero base nonzero shift.

If I recall that incorrectly, then you are right, we may just skip searching between 4Gb and 32Gb since we just did that in the zero-based step.

[RealFYang]

Hi Thomas,

Would not removing the zero-based search be simpler then? We would forfeit the search for an area within 4g-32g then, but if I recall correctly, for bases between 4G and 16TB we use addiw + slli. In other words, we don't take advantage of zero base nonzero shift.

Yes, I think you are right. I don't see why range 4g-32g is special here either. And I have updated accordingly. Thanks.

[tstuefe]

LGTM. Thanks for fixing.

[feilongjiang]

Looks fine, thanks!

[RealFYang]

@tstuefe @feilongjiang : Thanks for the review!
/integrate

[openjdk]

Going to push as commit de02503.
Since your change was applied there have been 28 commits pushed to the master branch:

• 27646e5: 8344148: Add an explicit compiler phase for warning generation
• 8d388cc: 8346457: AOT cache creation crashes with "assert(pair_at(i).match() < pair_at(i+1).match()) failed: unsorted table entries"
• d723597: 8345432: (ch, fs) Replace anonymous Thread with InnocuousThread
• 9c393a2: 8346953: Remove unnecessary @SuppressWarnings annotations (client, Make "can write" check work on Windows #2)
• 9a60f44: 8345668: ZoneOffset.ofTotalSeconds performance regression
• 12700cb: 8346264: "Total compile time" counter should include time spent in failing/bailout compiles
• dd81f8d: 8344079: Minor fixes and cleanups to compiler lint-related code
• ccf3d57: 8346985: Convert test/jdk/com/sun/jdi/ClassUnloadEventTest.java to Class-File API
• 594e519: 8346984: Remove ASM-based benchmarks from Class-File API benchmarks
• c027f2e: 8346983: Remove ASM-based transforms from Class-File API tests
• ... and 18 more: https://git.openjdk.org/jdk/compare/6c59185475eeca83153f085eba27cc0b3acf9bb4...master

Your commit was automatically rebased without conflicts.

[openjdk]

@RealFYang Pushed as commit de02503.

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