Bug ID: JDK-8281429 PhiNode::Value() is too conservative for tripcount of CountedLoop

JDK-8281429 : PhiNode::Value() is too conservative for tripcount of CountedLoop

Type: Bug
Component: hotspot
Sub-Component: compiler
Affected Version: 19

Priority: P4
Status: Resolved
Resolution: Fixed

Submitted: 2022-02-08
Updated: 2025-06-10
Resolved: 2022-05-06

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JDK 19
19 b22Fixed

Related Reports

Causes :	JDK-8358889 - C2 hits assert in backend due to malformed uncommon trap
Relates :	JDK-8329535 - Wrong output of program running with jdk17u and oracle-jdk17-release
Relates :	JDK-8289748 - C2 compiled code crashes with SIGFPE with -XX:+StressLCM and -XX:+StressGCM
Relates :	JDK-8296077 - applications/javafuzzer/BigTest.java fails "assert(false) failed: graph should be schedulable" after JDK-8281429
Relates :	JDK-8295788 - C2 compilation hits "assert((mode == ControlAroundStripMined && use == sfpt) \|\| !use->is_reachable_from_root()) failed: missed a node"
Relates :	JDK-8316396 - Endless loop in C2 compilation triggered by AddNode::IdealIL
Relates :	JDK-8292088 - C2: assert(is_OuterStripMinedLoop()) failed: invalid node class: IfTrue

Description

I noticed for a loop like:

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

PhiNode::Value() sets the type of i to [0, 10] when it's [0,9]

Comments

Changeset: fa1ca98f Author: Roland Westrelin <roland@openjdk.org> Date: 2022-05-06 08:24:33 +0000 URL: https://git.openjdk.java.net/jdk/commit/fa1ca98fff66fb91cfd5b00404645e0574d03101

06-05-2022

A pull request was submitted for review. URL: https://git.openjdk.java.net/jdk/pull/7823 Date: 2022-03-15 16:02:54 +0000

15-03-2022

ILW = Type range of iv phis are too wide which could prevent optimizations, no known cases where this limits performance, no workaround = MLH = P4

08-02-2022