8351660: C2: SIGFPE in unsigned_mod_value #24410

sarannat · 2025-04-03T10:29:08Z

Description :: The test program performs aLong.remainderUnsigned which triggers the call to the function unsigned_mod_value. At the end of unsigned_mod_value the expression, return TypeClass::make(static_cast<Signed>(dividend % divisor)), is computed which leads to a SIGFPE as the divisor in the test program is zero. The same behaviour was observed when the Long.remainderUnsigned was replaced with Integer.remainderUnsigned in the test program.

Solution :: The fix for JDK-8345766 emitted specific ModF/ModD nodes, which is optimized and converted to runtime calls after optimizations. This was done during parsing prior to JDK-8345766. In the scenario where there was unsigned modulo operation as in this test, there was no check for modulo by zero that could trigger an exception during runtime. The below fix proposes a check for modulo by zero and throws exception at runtime.

A Jtreg test has been added as part of this fix. This test case is based on the original test that resulted in the bug. @eme64 is the contributor of the original test. Thank you @eme64.

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Issue

JDK-8351660: C2: SIGFPE in unsigned_mod_value (Bug - P2)

Reviewers

Emanuel Peter (@eme64 - Reviewer) Review applies to 667c7e7a
Christian Hagedorn (@chhagedorn - Reviewer)
Damon Fenacci (@dafedafe - Committer)

Contributors

Emanuel Peter <[email protected]>

Reviewing

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$ git checkout pull/24410

Update a local copy of the PR:
$ git checkout pull/24410
$ git pull https://git.openjdk.org/jdk.git pull/24410/head

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$ git pr checkout 24410

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bridgekeeper · 2025-04-03T10:29:56Z

👋 Welcome back sarannat! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2025-04-03T10:30:08Z

@sarannat 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:

8351660: C2: SIGFPE in unsigned_mod_value

Co-authored-by: Emanuel Peter <[email protected]>
Reviewed-by: chagedorn, dfenacci, epeter

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 422 new commits pushed to the master branch:

c447a10: 8353856: Deprecate FlighRecorderPermission class for removal
4f80437: 8353842: C2: Add graph dumps before and after loop opts phase
bcac42a: 8349479: C2: when a Type node becomes dead, make CFG path that uses it unreachable
... and 419 more: https://git.openjdk.org/jdk/compare/7e3bc81e885071352fceab01015d7deef067a27a...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.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@eme64, @chhagedorn, @dafedafe) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

openjdk · 2025-04-03T10:30:50Z

@sarannat The following label will be automatically applied to this pull request:

hotspot-compiler

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

mlbridge · 2025-04-03T20:11:08Z

Webrevs

dafedafe · 2025-04-04T09:19:12Z

Thanks for the fix @sarannat!

Do you think we could add the failing test as regression test (maybe in the already available Mod tests, without creating a new test file)?

eme64

@sarannat Good work :)

test/hotspot/jtreg/compiler/integerArithmetic/TestUnsignedModByZero.java

chhagedorn

Looks good!

chhagedorn · 2025-04-09T05:46:06Z

src/hotspot/share/opto/divnode.cpp

@@ -1319,6 +1319,11 @@ static const Type* unsigned_mod_value(PhaseGVN* phase, const Node* mod) {
    return TypeClass::ZERO;
  }

+  // Mod by zero?  Throw exception at runtime!


Suggested change

// Mod by zero? Throw exception at runtime!

// Mod by zero? Throw an exception at runtime!

chhagedorn · 2025-04-09T05:46:26Z

test/hotspot/jtreg/compiler/integerArithmetic/TestUnsignedModByZero.java

+    }
+
+     public static void main(String[] args) {
+        for (int i =0; i < 10_000; i++) {


Suggested change

for (int i =0; i < 10_000; i++) {

for (int i = 0; i < 10_000; i++) {

dafedafe

Looks good to me otherwise.

dafedafe · 2025-04-09T08:01:56Z

test/hotspot/jtreg/compiler/integerArithmetic/TestUnsignedModByZero.java

+/*
+ * @test
+ * @bug 8351660
+ * @summary Test that modulo by zero throws exception at runtime in case of unsigned values.


Suggested change

* @summary Test that modulo by zero throws exception at runtime in case of unsigned values.

* @summary Test that modulo by zero throws an exception at runtime in case of unsigned values.

sarannat · 2025-04-10T07:47:55Z

/contributor add @eme64

sarannat · 2025-04-10T07:48:13Z

Thank you for the reviews.

openjdk · 2025-04-10T07:48:42Z

@sarannat
Contributor Emanuel Peter <[email protected]> successfully added.

sarannat · 2025-04-10T07:50:19Z

/integrate

openjdk · 2025-04-10T07:51:23Z

@sarannat
Your change (at version 2162324) is now ready to be sponsored by a Committer.

dafedafe · 2025-04-10T07:58:23Z

/sponsor

openjdk · 2025-04-10T07:59:10Z

Going to push as commit 04e2a06.
Since your change was applied there have been 423 commits pushed to the master branch:

73c8c75: 8351157: Clean up x86 GC barriers after 32-bit x86 removal
c447a10: 8353856: Deprecate FlighRecorderPermission class for removal
4f80437: 8353842: C2: Add graph dumps before and after loop opts phase
... and 420 more: https://git.openjdk.org/jdk/compare/7e3bc81e885071352fceab01015d7deef067a27a...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-04-10T07:59:17Z

@dafedafe @sarannat Pushed as commit 04e2a06.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

JDK-8351660: C2: SIGFPE in unsigned_mod_value

fb407aa

openjdk bot added the hotspot-compiler [email protected] label Apr 3, 2025

sarannat marked this pull request as ready for review April 3, 2025 20:06

openjdk bot added the rfr Pull request is ready for review label Apr 3, 2025

sarannat marked this pull request as draft April 4, 2025 08:21

openjdk bot removed the rfr Pull request is ready for review label Apr 4, 2025

added jtreg test

3bce2b2

sarannat force-pushed the JDK-8351660 branch from e1ed3cd to 3bce2b2 Compare April 8, 2025 13:06

sarannat marked this pull request as ready for review April 8, 2025 13:11

openjdk bot added the rfr Pull request is ready for review label Apr 8, 2025

eme64 suggested changes Apr 8, 2025

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test/hotspot/jtreg/compiler/integerArithmetic/TestUnsignedModByZero.java Outdated Show resolved Hide resolved

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8351660: C2: SIGFPE in unsigned_mod_value #24410

8351660: C2: SIGFPE in unsigned_mod_value #24410

sarannat commented Apr 3, 2025 •

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	// Mod by zero? Throw exception at runtime!
	// Mod by zero? Throw an exception at runtime!

	for (int i =0; i < 10_000; i++) {
	for (int i = 0; i < 10_000; i++) {

	* @summary Test that modulo by zero throws exception at runtime in case of unsigned values.
	* @summary Test that modulo by zero throws an exception at runtime in case of unsigned values.

8351660: C2: SIGFPE in unsigned_mod_value #24410

8351660: C2: SIGFPE in unsigned_mod_value #24410

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sarannat commented Apr 3, 2025 • edited by openjdk bot Loading

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