8353815: [ubsan] compilationPolicy.cpp: division by zero related to tiered compilation flags

[mhaessig]

A run of runtime/CommandLine/OptionsValidation/TestOptionsWithRanges.java with an ubsan enabled binary revealed that passing the value 0 to Tier(3|4)LoadFeedback, and TieredRateUpdateMinTime lead to division by zero.

Since Tier(3|4)LoadFeedback should disable the scaling of the compilation thresholds, 8bf37ee special cases the 0 case to disable scaling and documents it accordingly.

4893b28 sets the lower limit for TieredRateUpdate(Min|Max)Time to 1 since the code assumes that at least 1ms passes between each event:

jdk/src/hotspot/share/compiler/compilationPolicy.cpp

Lines 968 to 974 in c4fb00a

	// We should be running for at least 1ms.
	if (delta_s >= TieredRateUpdateMinTime) {
	// And we must've taken the previous point at least 1ms before.
	if (delta_t >= TieredRateUpdateMinTime && delta_e > 0) {
	method->set_prev_time(t);
	method->set_prev_event_count(event_count);
	method->set_rate((float)delta_e / (float)delta_t); // Rate is events per millisecond

This PR was tested with:

• Github Actions
• tier1 and 2 plus Oracle internal testing on Oracle supported platforms

---

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Issue

• JDK-8353815: [ubsan] compilationPolicy.cpp: division by zero related to tiered compilation flags (Bug - P4)

Reviewers

• Matthias Baesken (@MBaesken - Reviewer)
• Vladimir Kozlov (@vnkozlov - Reviewer)

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[openjdk]

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8353815: [ubsan] compilationPolicy.cpp: division by zero related to tiered compilation flags

Reviewed-by: mbaesken, kvn

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At the time when this comment was updated there had been 29 new commits pushed to the master branch:

• c6ab63d: 8359735: [Ubuntu 25.10] java/lang/ProcessBuilder/Basic.java, java/lang/ProcessHandle/InfoTest.java fail due to rust-coreutils
• ff54a64: 8360049: CodeInvalidationReasonTest.java fails with ZGC on AArch64
• c11f36e: 8356708: C2: loop strip mining expansion doesn't take sunk stores into account
• ... and 26 more: https://git.openjdk.org/jdk/compare/57266064a7bb995c3c614c19b936687af35e9aa4...master

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[mlbridge]

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• 00: Full (4893b288)

[vnkozlov]

Good