Is th.flurw from xtheadfmemidx really supported on RV32?

XUANTIE-RV / thead-extension-spec

XuanTie vendor extension Instruction Set spec

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Is th.flurw from xtheadfmemidx really supported on RV32? #49

Open topperc opened 4 months ago

topperc commented 4 months ago

The xtheadfmemidx doc says "All instructions are available for RV32 and RV64". But th.flurw seems identical to th.flrw on RV32.

I found this patch that removed some of the "u" instructions from RV32 for xtheadmemidx. https://github.com/T-head-Semi/thead-extension-spec/commit/5d38f4f87a1ebe297e60c3c5944cdc527b8e3e88

cmuellner commented 4 months ago

We should drop th.flurw from RV32, just like we did with th.lur* and th.sur* in the referenced change for the XTheadMemidx extension. The whole table in the XTheadFMemIdx seems to be incorrect and deserves a rework.

Afaik, there is no implementation of XTheadFMemIdx in any of T-Head's RV32 cores. The E902 and the E906 only implement XTheadCmo and XTheadSync. So we can safely edit the spec (and all implementations that follow) without worrying too much.