Integrated: 8253588: C1: assert(false) failed: unknown register on x86_32 only with -XX:+TraceLinearScanLevel=4

[Christian Hagedorn]

On Fri, 25 Sep 2020 10:07:04 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

> [JDK-8251093](https://bugs.openjdk.java.net/browse/JDK-8251093) introduced some additional logging of intervals and its
> registers in various places. On 32-bit only, we could have two registers for an interval. A hi-register is only used
> when the interval has `_num_phys_regs` set to 2. In one such place
> ([L5448](https://github.com/chhagedorn/jdk/blob/29ed779487bad3c359fb13dfad3f41832637a470/src/hotspot/share/c1/c1_LinearScan.cpp#L5448)),
> we log the hi-register `hint_regHi`. On
> [L5441](https://github.com/chhagedorn/jdk/blob/29ed779487bad3c359fb13dfad3f41832637a470/src/hotspot/share/c1/c1_LinearScan.cpp#L5441),
> however, we can assign it an invalid register number when `_num_phys_regs` is 1. That was not a problem before
> JDK-8251093 as we only used `hint_regHi` later after a `_num_phys_regs == 2` check on
> [L5484](https://github.com/chhagedorn/jdk/blob/29ed779487bad3c359fb13dfad3f41832637a470/src/hotspot/share/c1/c1_LinearScan.cpp#L5484).
> But the additional logging is performed earlier resulting in this assertion failure when trying to log the invalid
> `hint_regHi` register.  Thanks, Christian

This pull request has now been integrated.

Changeset: 13fe054c
Author:    Christian Hagedorn <chagedorn at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/13fe054c
Stats:     1 line in 1 file changed: 0 ins; 0 del; 1 mod

8253588: C1: assert(false) failed: unknown register on x86_32 only with -XX:+TraceLinearScanLevel=4

Reviewed-by: thartmann, kvn

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PR: https://git.openjdk.java.net/jdk/pull/356