On 9/10/21 3:36 PM, Philipp Tomsich wrote:
> Richard,
>
> Did you have a chance to consider what to do with clzw?
> I would prefer to avoid the extra extension instructions and change the implementation
> (and would update the commit message to provide more context), but if you insist on
> setting 'ctx->w' I'll just have the extra extensions emitted than delay this series further…
I don't mind not setting ctx->w, but bear in mind that UXL is going to automatically set
this flag when executing RV32 on RV64. That's why I have written a tcg patch set to
eliminate unnecessary sign-extensions.
Ok, thanks! Updated patches follow, once all test workloads have run…
Just wondering regarding the UXL-comment: the clzw instruction will be an illegal encoding for RV32 (the w-form instructions are present on RV64 only), so it should never be encountered in a RV32 instruction stream. Did you mean that clz (the instruction operating on xlen-registers) would have ctx->w set for RV32 executing on RV64 ... or am I missing something fundamental?
Philipp.