"'** Like other types in ispc, pointers are varying by default, if an explicit uniform qualifier isn't provided. However, the default variability of the pointed-to type is uniform. "
Thank you Deepak, this was the bit I was missing. Cheers, Pete On Wed, Jan 13, 2021 at 9:46 PM Deepak Rajendrakumaran < [email protected]> wrote: > Hi guys, > > If I understand correctly, we are discussing 2 different things here. Feel > free to point out and correct me if I understand either incorrectly. > > *Issue 1 - Reason for warning getting added* > This was mainly to avoid confusion for the user since varying is an ISPC > feature and generally forbidden from exporting to cpp side outside of > exceptions like this. > We decided to add it, looking at the function signatures created for > c-side header files by ispc for varying types and possibility of users > finding it confusing. > Note : To create header to check - ispc <input_file.ispc> *-h* > <header_file.h> > > For eg. > Ispc function: export void test2( varying float *uniform src, varying > float *uniform dst ) { .. } > exported function signature in Header created : extern void test2(float( * > src)[8], float( * dst)[8]); // the [8] here is because is 8 wide(varying) > since i compiled for avx2-i32x8 . > Varying though represented as vectors internally in ispc IR is represented > as arrays in headers. > > > Similarly array > Ispc Function : export void test3(float src[20], float dst[20]) > exported function signature in Header created : extern void test3(float( > * src)[8], float( * dst)[8]); // the [8] here is because is 8 wide(varying) > since i compiled for avx2-i32x8. > > Reference to compare IR for ISPC and corresponding function signature in > header > Ispc - https://ispc.godbolt.org/z/TPhv5n > header : https://godbolt.org/z/brod78 > > If you prefer to remove the warning, one option is to use 'pragma ignore > warning ' before the function. See perfbench.ispc here - > https://github.com/ispc/ispc/commit/761de37d076c64dbf8f74226a3b1f88fcb8fdc1e > > > *Issue 2 - variability of pointer type* > > Looking at Pete's code - https://ispc.godbolt.org/z/76dajK > > The below excerpt is from the ispc documentation - > https://ispc.github.io/ispc.html#pointer-types > '** Like other types in ispc, pointers are varying by default, if an > explicit uniform qualifier isn't provided. However, the default > variability of the pointed-to type is uniform. ** This rule will be > illustrated and explained in examples below.' > > So , > int * uniform var = uniform int *uniform var > int * var = uniform int * varying var > > Considering the above, you are right that default Variability is 'varying' > but pointed-to type for pointers is an exception. > So, the current behaviour seems correct to me. > > Note - we do have a typecast buf for Variability now- > https://github.com/ispc/ispc/pull/1978 . But, that's not immediately > related to this. > > > Regards, > Deepak > > > On Wed, Jan 13, 2021 at 7:00 PM Pete Brubaker <[email protected]> wrote: > >> I'm fairly certain this warning was added because varying is the default >> specifier for types and can possibly confuse people new to the language. >> However it doesn't look like it's working as intended. >> >> https://ispc.godbolt.org/z/76dajK >> >> It looks like pointer parameters on exported functions aren't >> automatically promoted varying. However pass by value types are. >> >> Cheers, >> >> Pete >> >> >> >> On Wed, Jan 13, 2021 at 3:22 PM Marianna Neubauer < >> [email protected]> wrote: >> >>> Hello, >>> >>> Since uniform pointers to varying types are permitted for an exported >>> function, I don't understand why this warrants a warning. What was the >>> motivation for adding this warning? >>> >>> Thank you, >>> Marianna >>> >>> On Monday, November 9, 2020 at 5:36:42 PM UTC-8 Deepak Rajendrakumaran >>> wrote: >>> >>>> Hello, >>>> >>>> Yes, this was an expected change - >>>> https://github.com/ispc/ispc/commit/761de37d076c64dbf8f74226a3b1f88fcb8fdc1e >>>> >>>> Functionally there is not change but a warning got added. You should >>>> still be able to compile and run your code, but it'll print the warning . >>>> 'Warning: Exported function parameter "ptr" points to varying type' merely >>>> lets the user know they are dealing with a varying type. >>>> >>>> -Deepak >>>> >>>> On Monday, November 9, 2020 at 2:33:16 PM UTC-8 [email protected] >>>> wrote: >>>> >>>>> >>>>> An exported function (at least up to 1.12) happily accepted parameters >>>>> of the form: >>>>> >>>>> varying TYPE * uniform ptr >>>>> >>>>> I am trying out 1.14.1 and get the following error: >>>>> >>>>> test.ispc:2:19: Warning: Exported >>>>> function parameter "ptr" points >>>>> to varying type >>>>> run(varying float * uniform ptr) >>>>> >>>>> From this code: >>>>> >>>>> export void >>>>> run(varying float * uniform ptr) >>>>> { >>>>> } >>>>> >>>>> The code compiles as expected at least up to 1.12. >>>>> >>>>> Is this an expected change? I didn't see anything about it in the >>>>> release notes. >>>>> >>>>> Cheers, >>>>> -Brian >>>>> >>>>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Intel SPMD Program Compiler Users" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/ispc-users/3240f3c9-1fc2-462e-b3de-6f07ffc61a93n%40googlegroups.com >>> <https://groups.google.com/d/msgid/ispc-users/3240f3c9-1fc2-462e-b3de-6f07ffc61a93n%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- >> You received this message because you are subscribed to the Google Groups >> "Intel SPMD Program Compiler Users" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/ispc-users/CAH0mFKAD4XqeHkVe_C0958oTeVo38ZZvQYHaGPL_u1vRWmJ5kQ%40mail.gmail.com >> <https://groups.google.com/d/msgid/ispc-users/CAH0mFKAD4XqeHkVe_C0958oTeVo38ZZvQYHaGPL_u1vRWmJ5kQ%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups > "Intel SPMD Program Compiler Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/ispc-users/CAAV9i%3D4gZThb%2Boeo70jYiDmTPcXkyo2P9g9Tk7KfY%3DWrY%3DSzVg%40mail.gmail.com > <https://groups.google.com/d/msgid/ispc-users/CAAV9i%3D4gZThb%2Boeo70jYiDmTPcXkyo2P9g9Tk7KfY%3DWrY%3DSzVg%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Intel SPMD Program Compiler Users" group. 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