RFR: 8276108: Wrong instruction generation in aarch64 backend

[Nick Gasson]

On Mon, 22 Nov 2021 13:08:54 GMT, Andrew Haley <aph at openjdk.org> wrote:

> We surely need a reproducer for this one.

For this to cause a problem we'd need C1 to generate an unaligned load/store with a constant offset. I don't think that can happen in current mainline JDK (or else we would have already seen failures). However `addr->scale()` is always zero when the offset is a constant so the current code isn't functioning as intended.

The valhalla branch below asserts with "Field too big for insn" due to this when you run the hotspot_valhalla jtreg group (commit e903390):

https://github.com/fparain/valhalla/tree/c1_cleanup

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PR: https://git.openjdk.java.net/jdk/pull/6212