ye-luo added inline comments.
================
Comment at: clang/test/OpenMP/target_data_use_device_addr_codegen_ptr.cpp:14
+ {
+ #pragma omp target data use_device_addr(x)
+ {
----------------
doru1004 wrote:
> ye-luo wrote:
> > doru1004 wrote:
> > > ye-luo wrote:
> > > > doru1004 wrote:
> > > > > ye-luo wrote:
> > > > > > In my understanding of the spec.
> > > > > > `map(tofrom:x[0:256])` only maps the memory segment that x points
> > > > > > to. x itself as a pointer scalar is not mapped.
> > > > > > use_device_addr(x) should fail to find the map of x scalar.
> > > > > > 5.2 spec.
> > > > > > If the list item is not a mapped list item, it is assumed to be
> > > > > > accessible on the target device.
> > > > > > To me, it seems just keep &x as it was, in this case &x remains a
> > > > > > host address.
> > > > > >
> > > > > > But in your patch description, it seems treating x differently from
> > > > > > a scalar.
> > > > > >
> > > > > > I also applied your patch on main and got segfault because the x
> > > > > > has a value of device address and x[0] fails. This should be the
> > > > > > behavior of use_device_ptr instead of use_device_addr.
> > > > > > To me, it seems just keep &x as it was, in this case &x remains a
> > > > > > host address.
> > > > >
> > > > > So does this mean that if I do something like this in the target data
> > > > > I should get different addresses for x:
> > > > >
> > > > >
> > > > > ```
> > > > > #pragma omp target data use_device_ptr(x)
> > > > > {
> > > > > fprintf(stderr, "x: %p\n", __LINE__, x);
> > > > > }
> > > > >
> > > > > #pragma omp target data use_device_addr(x)
> > > > > {
> > > > > fprintf(stderr, "x: %p\n", __LINE__, x);
> > > > > }
> > > > > ```
> > > > >
> > > > >
> > > > > > I also applied your patch on main and got segfault because the x
> > > > > > has a value of device address and x[0] fails.
> > > > >
> > > > > That's my fault x[0] was the wrong thing to use actually.
> > > > >
> > > > >
> > > > When you have an outer `target data map(x)`, then two printf differ. If
> > > > there is no outer `map(x)`, two printf should be identical.
> > > > When you have an outer `target data map(x)`, then two printf differ. If
> > > > there is no outer `map(x)`, two printf should be identical.
> > >
> > > This is super helpful thank you! I'll make sure that happens.
> > >
> > > In the case when an outer target data exists, the print of the x which is
> > > under use_device_addr should print the same address as printing x on the
> > > host?
> > I need a correction. When outer map(x) exists, actually the address(not
> > value) of x should be a device address, and the code cannot even print x.
> > Printing &x should be fine.
> In the context of the above comment, should &x on the device be an address I
> can verify, somehow, to make sure that it's correct or is it a completely new
> device address?
>
> So for example, should it be the same as when I do a use_device_ptr but print
> the &x in that case? (With the current master those two addresses are not the
> same.)
>
> I guess what I need is an example of using use_device_addr that actually does
> something meaningful because with the current main branch printing the &x of
> a use_device_addr(x) is nil.
When an outer map(x) is placed, &x does print something meaningful.
I tried to access `omp_get_mapped_ptr(&x, omp_get_default_device())` but got
link time error about missing omp_get_mapped_ptr definition. It seems missing
an implementation of this OpenMP API.
When there is no map(x), I also got nil, I think this is a bug, &x should keep
the host value.
I cannot think of a useful example with use_device_addr(x) where x is a
pointer. But x can be a scalar float.
and then call cublas gemm, the alpha/beta parameter can be &x.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D133694/new/
https://reviews.llvm.org/D133694
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