RFR: 8370871: [s390x] consistently update top_frame_sp

[Richard Reingruber]

On Wed, 29 Oct 2025 09:40:34 GMT, Amit Kumar <amitkumar at openjdk.org> wrote:

> Stores top_frame_sp for interpreter frames consistently. Although this is making one to assert fail in loom port but still I think this should be considered independent bug.

I noticed [this store of top_frame_sp](https://github.com/openjdk/jdk/blob/4a0200caf98ecb9bd1e6fe2670e79b36616a45fe/src/hotspot/cpu/s390/interp_masm_s390.cpp#L582). It shouldn't be necessary. I'd replace it with an assertion that the stored value is equal to the value in memory (as it is done [here](https://github.com/openjdk/jdk/blob/6817e8cfaf71ee4651f449abbcb863b9ed05b15d/src/hotspot/cpu/ppc/interp_masm_ppc_64.cpp#L1065-L1070)).

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PR Comment: https://git.openjdk.org/jdk/pull/28042#issuecomment-3461086402