JDK-8301491: C2: java.lang.StringUTF16::indexOfChar intrinsic called with negative character argument

[dafedafe]

The java.lang.StringUTF16::indexOfChar is supposed to return -1 for characters with value < 0. Its intrinsic methods don't always do so.

jdk/src/java.base/share/classes/java/lang/StringUTF16.java

Line 535 in 96c50a3

private static int indexOfChar(byte[] value, int ch, int fromIndex, int max) {

The intrinsic methods expect the int character being passed to be >= 0. Unfortunately this is not enforced in the Java part (indexOf only checks for the upper bound):

jdk/src/java.base/share/classes/java/lang/StringUTF16.java

Line 430 in 96c50a3

if (ch < Character.MIN_SUPPLEMENTARY_CODE_POINT) {

The intrinsic methods assume that only the lower 16 bits are used (0 <= ch <= 0xFFFF) and either don't care about the upper 16 bits or implicitly mask them, e.g. for aarch64:

jdk/src/hotspot/cpu/aarch64/c2_MacroAssembler_aarch64.cpp

Lines 502 to 503 in 96c50a3

	orr(ch, ch, ch, LSL, 16);
	orr(ch, ch, ch, LSL, 32);

or avx:

jdk/src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp

Line 3039 in 96c50a3

vpbroadcastw(vec1, vec1, Assembler::AVX_256bit);

On the other hand, the Java method indexOfCharUnsafe makes this check implicitly by comparing a char with an int;

jdk/src/java.base/share/classes/java/lang/StringUTF16.java

Lines 542 to 544 in 96c50a3

	if (getChar(value, i) == ch) {
	return i;
	}

As there doesn't seem to be a good reason to call indexOfChar with ch < 0, it seems reasonable to add a check in LibraryCallKit::inline_string_indexOfChar that triggers a deoptimization if it fails.

---

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Issue

• JDK-8301491: C2: java.lang.StringUTF16::indexOfChar intrinsic called with negative character argument

Reviewers

• Tobias Hartmann (@TobiHartmann - Reviewer)
• Vladimir Kozlov (@vnkozlov - Reviewer)

Reviewing

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[TobiHartmann]

Looks good to me.

[openjdk]

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

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

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

8301491: C2: java.lang.StringUTF16::indexOfChar intrinsic called with negative character argument

Reviewed-by: thartmann, kvn

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 175 new commits pushed to the master branch:

• 49eb68b: 8296158: Refactor the verification of CDS region checksum
• 655a712: 8301444: Port fdlibm hyperbolic transcendental functions to Java
• b242eef: 8280419: Remove dead code related to VerifyThread and verify_thread()
• 4ce493f: 8302225: SunJCE Provider doesn't validate key sizes when using 'constrained' transforms for AES/KW and AES/KWP
• a39cf2e: 8301753: AppendFile/WriteFile has differences between make 3.81 and 4+
• de80dd9: 8296010: AssertionError in annotationTargetType
• e5042dd: 8302671: libawt has a memmove decay error
• 574b48c: 8302678: validate_source fails after JDK-8293313
• 90e0922: 8293313: NMT: Rework MallocLimit
• f558a6c: 8298276: JFR: Update NMT events to make use of common periodic timestamp feature
• ... and 165 more: https://git.openjdk.org/jdk/compare/96c50a3486e3b6cdce7f8fb409d015b289770811...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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[mlbridge]

Webrevs

• 00: Full (c07718bb)

[vnkozlov]

Good.

[dafedafe]

@TobiHartmann @vnkozlov thanks a lot for your reviews!

[dafedafe]

/integrate

[openjdk]

@dafedafe
Your change (at version c07718b) is now ready to be sponsored by a Committer.

[TobiHartmann]

/sponsor

[openjdk]

Going to push as commit 47ca577.
Since your change was applied there have been 175 commits pushed to the master branch:

• 49eb68b: 8296158: Refactor the verification of CDS region checksum
• 655a712: 8301444: Port fdlibm hyperbolic transcendental functions to Java
• b242eef: 8280419: Remove dead code related to VerifyThread and verify_thread()
• 4ce493f: 8302225: SunJCE Provider doesn't validate key sizes when using 'constrained' transforms for AES/KW and AES/KWP
• a39cf2e: 8301753: AppendFile/WriteFile has differences between make 3.81 and 4+
• de80dd9: 8296010: AssertionError in annotationTargetType
• e5042dd: 8302671: libawt has a memmove decay error
• 574b48c: 8302678: validate_source fails after JDK-8293313
• 90e0922: 8293313: NMT: Rework MallocLimit
• f558a6c: 8298276: JFR: Update NMT events to make use of common periodic timestamp feature
• ... and 165 more: https://git.openjdk.org/jdk/compare/96c50a3486e3b6cdce7f8fb409d015b289770811...master

Your commit was automatically rebased without conflicts.

[openjdk]

@TobiHartmann @dafedafe Pushed as commit 47ca577.

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