There isn't really such a thing as "sign-extending a uint", as "uint" means "unsigned int". Zero-extension is the only extension that makes sense for uint32.
I think we zero-extend most 32-bit values in V8, however there are a few cases where we must explicitly sign-extend: specifically when a (signed) int32 will be added to a 64-bit value, such as for address+offset computations. We do rely on 32-bit values being zero-extended in some places, so it's important to keep those tests working. (There *may* be room for significant cleanup/redesign there; but our historical experience is that bugs very easily slip in there, so I'd rather not change any assumptions unless there's a *really* strong reason to do so.) On Mon, Jul 26, 2021 at 2:31 PM Zhao Jiazhong <zhaojiazhong...@loongson.cn> wrote: > Hello everyone, > > AFAIK, MIPS64 and RV64 don't have 32-bit registers and according to > their calling convention, they would sign-extend all 32-bit values when > they are stored in 64-bit registers, both signed and unsigned, see: A > related question in stackoverflow > <https://stackoverflow.com/questions/52646216/zero-sign-extend-are-no-op-why-then-instructions-for-each-size-type> > . > > But in v8 it seems the uint32 values are zero-extended? I tried to > sign-extend uint32 values, on mips64, which could elide some instructions, > and only two more tests failed: > - cctest/test-run-load-store/RunLoadStoreZeroExtend64 > - cctest/test-run-load-store/RunUnalignedLoadStoreZeroExtend64 > Just like their names suggest, they both may load some values and check > whether they are zero-extended. > > So I wonder could uint32 values be sign-extended in v8 on MIPS64? Any > suggestion would be appreciated, thanks! > > Thanks, > Zhao Jiazhong > > -- > > -- -- v8-dev mailing list v8-dev@googlegroups.com http://groups.google.com/group/v8-dev --- You received this message because you are subscribed to the Google Groups "v8-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to v8-dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/v8-dev/CAKSzg3Q945XuHZR_rRcy0mVLaa%2B-3HiO6ST7cmd9Cg2VqvCrLA%40mail.gmail.com.
