[jdk25u-dev] RFR: 8369881: C2: Unexpected node in SuperWord truncation: ReverseBytesS, ReverseBytesUS

[Vishal Chand]

On Wed, 4 Feb 2026 23:10:41 GMT, Vishal Chand <duke at openjdk.org> wrote:

> Clean backport of [8369881](https://github.com/openjdk/jdk/commit/aa194c6a5a21aca64d454e4c5eeed1464c8f190b): C2: Unexpected node in SuperWord truncation: ReverseBytesS, ReverseBytesUS
> 
> Fixes fuzzer-discovered assert failure in SuperWord truncation for ReverseBytesS and ReverseBytesUS nodes. Adds missing nodes to truncation switch statement and includes test cases for both.
> 
> Additional Testing:
> - [x] New regression test fails without the fix, passes with it.
> - [x] Linux x86_64 server fastebug compiler tests.

\approval request for Clean backport of [8369881](https://github.com/openjdk/jdk/commit/aa194c6a5a21aca64d454e4c5eeed1464c8f190b): C2: Unexpected node in SuperWord truncation: ReverseBytesS, ReverseBytesUS

This is a low risk fix adding 2 missing node types to Superword non-truncation list. Fixes debug assert failure with no impact in product.

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PR Comment: https://git.openjdk.org/jdk25u-dev/pull/233#issuecomment-3853678186