ye-luo added inline comments.
================
Comment at: openmp/libomptarget/src/omptarget.cpp:233
MapperComponents
- .Components[target_data_function == targetDataEnd ? I : E - I - 1];
+ .Components[target_data_function == targetDataEnd ? E - I - 1 : I];
MapperArgsBase[I] = C.Base;
----------------
ABataev wrote:
> ye-luo wrote:
> > ye-luo wrote:
> > > ye-luo wrote:
> > > > ABataev wrote:
> > > > > ABataev wrote:
> > > > > > ye-luo wrote:
> > > > > > > ye-luo wrote:
> > > > > > > > ye-luo wrote:
> > > > > > > > > ABataev wrote:
> > > > > > > > > > ye-luo wrote:
> > > > > > > > > > > ABataev wrote:
> > > > > > > > > > > > ABataev wrote:
> > > > > > > > > > > > > ye-luo wrote:
> > > > > > > > > > > > > > ye-luo wrote:
> > > > > > > > > > > > > > > ABataev wrote:
> > > > > > > > > > > > > > > > ye-luo wrote:
> > > > > > > > > > > > > > > > > ABataev wrote:
> > > > > > > > > > > > > > > > > > grokos wrote:
> > > > > > > > > > > > > > > > > > > What is the current status of the order
> > > > > > > > > > > > > > > > > > > of the arguments clang emits? Is it still
> > > > > > > > > > > > > > > > > > > necessary to traverse arguments in
> > > > > > > > > > > > > > > > > > > reverse order here?
> > > > > > > > > > > > > > > > > > Yes, still required
> > > > > > > > > > > > > > > > > Based on the conversation in
> > > > > > > > > > > > > > > > > https://reviews.llvm.org/D85216
> > > > > > > > > > > > > > > > > This line of code neither before nor after
> > > > > > > > > > > > > > > > > the change plays well.
> > > > > > > > > > > > > > > > > Shall we fix the order in targetDataEnd first?
> > > > > > > > > > > > > > > > This change is part of this patch and cannot be
> > > > > > > > > > > > > > > > committed separately.
> > > > > > > > > > > > > > > I mean could you fix that issue as a parent of
> > > > > > > > > > > > > > > this patch?
> > > > > > > > > > > > > > > This change is part of this patch and cannot be
> > > > > > > > > > > > > > > committed separately.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > If fixing the reordering is part of this patch, I
> > > > > > > > > > > > > > should have seen "target_data_function ==
> > > > > > > > > > > > > > targetDataEnd ?" branches disappear.
> > > > > > > > > > > > > Nope, just with this patch. It reorders the maps and
> > > > > > > > > > > > > need to change the cleanup order too.
> > > > > > > > > > > > It works just like constructors/destructors: allocate
> > > > > > > > > > > > in direct order, deallocate in reversed to correctly
> > > > > > > > > > > > handle map order.
> > > > > > > > > > > The description says that "present and alloc mappings are
> > > > > > > > > > > processed first and then all others."
> > > > > > > > > > > Why the order of arguments in targetDataBegin,
> > > > > > > > > > > targetDataEnd and targetDataUpdate all get reversed.
> > > > > > > > > > Because this is for mappers. Mapper maps are ordered by the
> > > > > > > > > > compiler in the direct order (alloc, maps, delete) but when
> > > > > > > > > > we need to do exit, we need to release the data in reversed
> > > > > > > > > > order (deletes, maps, allocs).
> > > > > > > > > I was not making the question clear. My question about
> > > > > > > > > "reverse" is not about having a reverse order for
> > > > > > > > > targetDataBegin. My question was about "reversing" from the
> > > > > > > > > the old code. Your change put the opposite order for
> > > > > > > > > targetDataBegin, targetDataEnd and targetDataUpdate cases.
> > > > > > > > > I was not making the question clear. My question about
> > > > > > > > > "reverse" is not about having a reverse order for
> > > > > > > > > targetDataBegin. My question was about "reversing" from the
> > > > > > > > > the old code. Your change put the opposite order for
> > > > > > > > > targetDataBegin, targetDataEnd and targetDataUpdate cases.
> > > > > > > >
> > > > > > > > typo correction
> > > > > > > > I was not making the question clear. My question about
> > > > > > > > "reverse" is not about having a reverse order for
> > > > > > > > **targetDataEnd**. My question was about "reversing" from the
> > > > > > > > the old code. Your change put the opposite order for
> > > > > > > > targetDataBegin, targetDataEnd and targetDataUpdate cases.
> > > > > > > My separate question specifically for targetDataEnd is the
> > > > > > > following.
> > > > > > >
> > > > > > > In target(), we call
> > > > > > > ```
> > > > > > > targetDataBegin(args)
> > > > > > > { // forward order
> > > > > > > for (int32_t i = 0; i < arg_num; ++i) { ... }
> > > > > > > }
> > > > > > > launch_kernels
> > > > > > > targetDataEnd(args)
> > > > > > > { // reverse order
> > > > > > > for (int32_t I = ArgNum - 1; I >= 0; --I) { }
> > > > > > > }
> > > > > > > ```
> > > > > > >
> > > > > > > At a mapper,
> > > > > > > ```
> > > > > > > targetDataMapper
> > > > > > > {
> > > > > > > // generate args_reverse in reverse order for targetDataEnd
> > > > > > > targetDataEnd(args_reverse)
> > > > > > > }
> > > > > > > ```
> > > > > > > Are we actually getting the original forward order due to one
> > > > > > > reverse in targetDataMapper and second reverse in targetDataEnd?
> > > > > > > Is this the desired behavior? This part confused me. Do I miss
> > > > > > > something? Could you explain a bit?
> > > > > > Yes, something like this. targetDataEnd reverses the order of
> > > > > > mapping arrays. But mapper generator always generates mapping
> > > > > > arrays in the direct order (it fills mapping arrays that later
> > > > > > processed by the targetDataEnd function). We could fix this by
> > > > > > passing extra Boolean flag to the generator function but it means
> > > > > > the redesign of the mappers. That's why we have to reverse it in
> > > > > > the libomptarget.
> > > > > You can check it yourself. Apply the patch, restore the original
> > > > > behavior in libomptarget and run libomptarget tests. Mapper related
> > > > > tests will crash.
> > > > Stick with mapper generator always generating mapping arrays in the
> > > > direct order. The targetDataMapper reverse the mapping array and then
> > > > passes args_reverse into targetDataEnd. Inside targetDataEnd, mapping
> > > > Yes, something like this. targetDataEnd reverses the order of mapping
> > > > arrays. But mapper generator always generates mapping arrays in the
> > > > direct order (it fills mapping arrays that later processed by the
> > > > targetDataEnd function). We could fix this by passing extra Boolean
> > > > flag to the generator function but it means the redesign of the
> > > > mappers. That's why we have to reverse it in the libomptarget.
> > >
> > > Stick with mapper generator always generating mapping arrays in the
> > > direct order.
> > >
> > > In the targetDataBegin case, targetDataMapper keep direct order args and
> > > calls targetDataBegin(args) and targetDataBegin process args in direct
> > > order.
> > >
> > > In the targetDataEnd case, targetDataMapper reverses the mapping array
> > > and then passes args_reverse into targetDataEnd. Inside targetDataEnd,
> > > args_reverse are processed in reverse order. So targetDataEnd is actually
> > > processing the args in original direct order. This seems contradictory to
> > > the constructor/deconstructor like behavior that all the mappings must be
> > > processed in the actual reverse order in targetDataEnd.
> > >
> > > This is my understanding. The current code should be wrong but obviously
> > > the current code is working. So why the current code is working? what is
> > > inconsistent in my analysis. Could you point out the missing piece.
> > > You can check it yourself. Apply the patch, restore the original
> > > behavior in libomptarget and run libomptarget tests. Mapper related tests
> > > will crash.
> >
> > For sure without this line, tests would crash and that is why you included
> > this line of change in the patch. Since you made the change, you could
> > explain why, right?
> I changed and simplified codegen for the mapper generator without changing
> its interface. I could do this because of the new ordering, before we could
> not rely on it. But it also requires a change in the runtime.
> targetDataEnd calls targetDataMapper and targetDataMapper fills the array in
> the direct order, but targetDataEnd processes them in the reverse order, but
> mapper generator does not know about it. It also has to generate the data in
> the reverse order, just like targetDataEnd does.
>
> Before this patch mapper generator tried to do some ordering but it was not
> always correct. It was not expecting something like map(alloc:s) map(s.a)
> because it was not allowed by the compiler. That's why it worked before and
> won't work with this patch.
> PS. The change in the mapper generator is also required and cannot be
> separated. Without this mappers tests won't work.
I played a bit with your patch.
```
#pragma omp target exit data map(from: c.a[0:NUM], c.b[0:NU2M]) map(delete: c)
```
I put NUM=1024 and NU2M = 2048.
LIBOMPTARGET_DEBUG reports
```
Libomptarget --> Entry 0: Base=0x00007fff064080a8, Begin=0x00007fff064080a8,
Size=16, Type=0x0, Name=(null)
Libomptarget --> Entry 1: Base=0x00007fff064080a8, Begin=0x0000000000f9cbd0,
Size=4096, Type=0x1000000000012, Name=(null)
Libomptarget --> Entry 2: Base=0x00007fff064080b0, Begin=0x0000000000f86e10,
Size=8192, Type=0x1000000000012, Name=(null)
Libomptarget --> Entry 3: Base=0x00007fff064080a8, Begin=0x00007fff064080a8,
Size=16, Type=0x1000000000008, Name=(null)
```
Since targetDataEnd internally reverse the processing order, could you confirm
that the frontend was emitting entries 3,2,1,0?
I'm wondering if the frontend could emit 3, 0, 1, 2 so the processing order is
2,1,0,3? The spec requires struct element processed before the struct in
"target exit data"
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D86119/new/
https://reviews.llvm.org/D86119
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