TIFitis marked an inline comment as done.
TIFitis added inline comments.
================
Comment at:
mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp:1357
+/// Process MapOperands for Target Data directives.
+static LogicalResult processMapOperand(
+ llvm::IRBuilderBase &builder, LLVM::ModuleTranslation &moduleTranslation,
----------------
kiranchandramohan wrote:
> TIFitis wrote:
> > TIFitis wrote:
> > > TIFitis wrote:
> > > > kiranchandramohan wrote:
> > > > > kiranchandramohan wrote:
> > > > > > TIFitis wrote:
> > > > > > > TIFitis wrote:
> > > > > > > > kiranchandramohan wrote:
> > > > > > > > > TIFitis wrote:
> > > > > > > > > > kiranchandramohan wrote:
> > > > > > > > > > > TIFitis wrote:
> > > > > > > > > > > > kiranchandramohan wrote:
> > > > > > > > > > > > > Isn't it possible to sink this whole function into
> > > > > > > > > > > > > the OpenMPIRBuilder by passing it a list of
> > > > > > > > > > > > > `mapOpValue` and `mapTypeFlags`?
> > > > > > > > > > > > > `lvm::Value *mapOpValue =
> > > > > > > > > > > > > moduleTranslation.lookupValue(mapOp);`
> > > > > > > > > > > > >
> > > > > > > > > > > > > Did i miss something? Or is this in anticipation of
> > > > > > > > > > > > > more processing required for other types?
> > > > > > > > > > > > I'm not fully sure but we might need more MLIR related
> > > > > > > > > > > > things when supporting types other than
> > > > > > > > > > > > LLVMPointerType. Also there is a call to
> > > > > > > > > > > > mlir::LLVM::createMappingInformation.
> > > > > > > > > > > >
> > > > > > > > > > > > I guess it might still be possible to move most of it
> > > > > > > > > > > > to the IRBuilder, would you like me to do that?
> > > > > > > > > > > Callbacks are useful when there is frontend-specific
> > > > > > > > > > > handling that is required. If more types require to be
> > > > > > > > > > > handled then it is better to have the callback. We can
> > > > > > > > > > > revisit this after all types are handled. I assume, the
> > > > > > > > > > > current handling is for scalars and arrays of known-size.
> > > > > > > > > > I am a novice at FORTRAN so I'm not aware of all the types
> > > > > > > > > > and scenarios.
> > > > > > > > > >
> > > > > > > > > > I've tested the following cases and they work end-to-end:
> > > > > > > > > >
> > > > > > > > > > **Fortran:**
> > > > > > > > > > ```
> > > > > > > > > > subroutine openmp_target_data_region(a)
> > > > > > > > > > real :: a(*)
> > > > > > > > > > integer :: b(1024)
> > > > > > > > > > character :: c
> > > > > > > > > > integer, pointer :: p
> > > > > > > > > > !$omp target enter data map(to: a, b, c, p)
> > > > > > > > > > end subroutine openmp_target_data_region
> > > > > > > > > > ```
> > > > > > > > > >
> > > > > > > > > > **LLVM IR(** `flang-new -fc1 -emit-llvm -fopenmp test.f90
> > > > > > > > > > -o test.ll`** ):**
> > > > > > > > > >
> > > > > > > > > > ```
> > > > > > > > > > ; ModuleID = 'FIRModule'
> > > > > > > > > > source_filename = "FIRModule"
> > > > > > > > > > target datalayout =
> > > > > > > > > > "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
> > > > > > > > > > target triple = "x86_64-unknown-linux-gnu"
> > > > > > > > > >
> > > > > > > > > > %struct.ident_t = type { i32, i32, i32, i32, ptr }
> > > > > > > > > >
> > > > > > > > > > @0 = private unnamed_addr constant [13 x i8]
> > > > > > > > > > c"loc(unknown)\00", align 1
> > > > > > > > > > @1 = private unnamed_addr constant [56 x i8]
> > > > > > > > > > c";/home/akash/Documents/scratch/test2.f90;unknown;3;16;;\00",
> > > > > > > > > > align 1
> > > > > > > > > > @2 = private unnamed_addr constant [56 x i8]
> > > > > > > > > > c";/home/akash/Documents/scratch/test2.f90;unknown;4;18;;\00",
> > > > > > > > > > align 1
> > > > > > > > > > @3 = private unnamed_addr constant [56 x i8]
> > > > > > > > > > c";/home/akash/Documents/scratch/test2.f90;unknown;5;25;;\00",
> > > > > > > > > > align 1
> > > > > > > > > > @4 = private unnamed_addr constant [23 x i8]
> > > > > > > > > > c";unknown;unknown;0;0;;\00", align 1
> > > > > > > > > > @5 = private unnamed_addr constant %struct.ident_t { i32 0,
> > > > > > > > > > i32 2, i32 0, i32 22, ptr @4 }, align 8
> > > > > > > > > > @.offload_maptypes = private unnamed_addr constant [4 x
> > > > > > > > > > i64] [i64 1, i64 1, i64 1, i64 1]
> > > > > > > > > > @.offload_mapnames = private constant [4 x ptr] [ptr @0,
> > > > > > > > > > ptr @1, ptr @2, ptr @3]
> > > > > > > > > >
> > > > > > > > > > declare ptr @malloc(i64)
> > > > > > > > > >
> > > > > > > > > > declare void @free(ptr)
> > > > > > > > > >
> > > > > > > > > > define void @openmp_target_data_region_(ptr %0) {
> > > > > > > > > > %2 = alloca [4 x ptr], align 8
> > > > > > > > > > %3 = alloca [4 x ptr], align 8
> > > > > > > > > > %4 = alloca [4 x i64], align 8
> > > > > > > > > > %5 = alloca [1024 x i32], i64 1, align 4
> > > > > > > > > > %6 = alloca [1 x i8], i64 1, align 1
> > > > > > > > > > %7 = alloca { ptr, i64, i32, i8, i8, i8, i8 }, i64 1,
> > > > > > > > > > align 8
> > > > > > > > > > %8 = alloca ptr, i64 1, align 8
> > > > > > > > > > store ptr null, ptr %8, align 8
> > > > > > > > > > br label %entry
> > > > > > > > > >
> > > > > > > > > > entry: ; preds =
> > > > > > > > > > %1
> > > > > > > > > > %9 = getelementptr inbounds [4 x ptr], ptr %2, i32 0, i32 > > > > > > > > > > 0
> > > > > > > > > > store ptr %0, ptr %9, align 8
> > > > > > > > > > %10 = getelementptr inbounds [4 x ptr], ptr %3, i32 0,
> > > > > > > > > > i32 0
> > > > > > > > > > store ptr %0, ptr %10, align 8
> > > > > > > > > > %11 = getelementptr inbounds [4 x i64], ptr %4, i32 0,
> > > > > > > > > > i32 0
> > > > > > > > > > store i64 ptrtoint (ptr getelementptr (ptr, ptr null, i32
> > > > > > > > > > 1) to i64), ptr %11, align 8
> > > > > > > > > > %12 = getelementptr inbounds [4 x ptr], ptr %2, i32 0,
> > > > > > > > > > i32 1
> > > > > > > > > > store ptr %5, ptr %12, align 8
> > > > > > > > > > %13 = getelementptr inbounds [4 x ptr], ptr %3, i32 0,
> > > > > > > > > > i32 1
> > > > > > > > > > store ptr %5, ptr %13, align 8
> > > > > > > > > > %14 = getelementptr inbounds [4 x i64], ptr %4, i32 0,
> > > > > > > > > > i32 1
> > > > > > > > > > store i64 ptrtoint (ptr getelementptr (ptr, ptr null, i32
> > > > > > > > > > 1) to i64), ptr %14, align 8
> > > > > > > > > > %15 = getelementptr inbounds [4 x ptr], ptr %2, i32 0,
> > > > > > > > > > i32 2
> > > > > > > > > > store ptr %6, ptr %15, align 8
> > > > > > > > > > %16 = getelementptr inbounds [4 x ptr], ptr %3, i32 0,
> > > > > > > > > > i32 2
> > > > > > > > > > store ptr %6, ptr %16, align 8
> > > > > > > > > > %17 = getelementptr inbounds [4 x i64], ptr %4, i32 0,
> > > > > > > > > > i32 2
> > > > > > > > > > store i64 ptrtoint (ptr getelementptr (ptr, ptr null, i32
> > > > > > > > > > 1) to i64), ptr %17, align 8
> > > > > > > > > > %18 = getelementptr inbounds [4 x ptr], ptr %2, i32 0,
> > > > > > > > > > i32 3
> > > > > > > > > > store ptr %7, ptr %18, align 8
> > > > > > > > > > %19 = getelementptr inbounds [4 x ptr], ptr %3, i32 0,
> > > > > > > > > > i32 3
> > > > > > > > > > store ptr %7, ptr %19, align 8
> > > > > > > > > > %20 = getelementptr inbounds [4 x i64], ptr %4, i32 0,
> > > > > > > > > > i32 3
> > > > > > > > > > store i64 ptrtoint (ptr getelementptr (ptr, ptr null, i32
> > > > > > > > > > 1) to i64), ptr %20, align 8
> > > > > > > > > > %21 = getelementptr inbounds [4 x ptr], ptr %2, i32 0,
> > > > > > > > > > i32 0
> > > > > > > > > > %22 = getelementptr inbounds [4 x ptr], ptr %3, i32 0,
> > > > > > > > > > i32 0
> > > > > > > > > > %23 = getelementptr inbounds [4 x i64], ptr %4, i32 0,
> > > > > > > > > > i32 0
> > > > > > > > > > call void @__tgt_target_data_begin_mapper(ptr @5, i64 -1,
> > > > > > > > > > i32 4, ptr %21, ptr %22, ptr %23, ptr @.offload_maptypes,
> > > > > > > > > > ptr @.offload_mapnames, ptr null)
> > > > > > > > > > ret void
> > > > > > > > > > }
> > > > > > > > > >
> > > > > > > > > > ; Function Attrs: nounwind
> > > > > > > > > > declare void @__tgt_target_data_begin_mapper(ptr, i64, i32,
> > > > > > > > > > ptr, ptr, ptr, ptr, ptr, ptr) #0
> > > > > > > > > >
> > > > > > > > > > ; Function Attrs: nounwind
> > > > > > > > > > declare void @__tgt_target_data_end_mapper(ptr, i64, i32,
> > > > > > > > > > ptr, ptr, ptr, ptr, ptr, ptr) #0
> > > > > > > > > >
> > > > > > > > > > attributes #0 = { nounwind }
> > > > > > > > > >
> > > > > > > > > > !llvm.module.flags = !{!0}
> > > > > > > > > >
> > > > > > > > > > !0 = !{i32 2, !"Debug Info Version", i32 3}
> > > > > > > > > > ```
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > If I am missing some important types here then please let
> > > > > > > > > > me know, I'll try to see if they work and if not I'll add
> > > > > > > > > > support for them in further patches.
> > > > > > > > > In general how are you passing the size of the fortran
> > > > > > > > > variable/type to the OpenMP runtime? For scalars and arrays
> > > > > > > > > with sizes known at compile time, this comes from the type
> > > > > > > > > itself. But for other types like assumed-shape arrays,
> > > > > > > > > variable length arrays this information comes from the
> > > > > > > > > descriptor or from other fields. My question is how is this
> > > > > > > > > being collected and passed to the runtime?
> > > > > > > > >
> > > > > > > > > For all the types, I see the following code in the IR you
> > > > > > > > > gave above for generating the `ArgSizes` argument of
> > > > > > > > > `__tgt_target_data_begin_mapper`. I don't understand how the
> > > > > > > > > code (and size) be the same for all the types.
> > > > > > > > > ```
> > > > > > > > > ...
> > > > > > > > > %11 = getelementptr inbounds [4 x i64], ptr %4, i32 0, i32 0
> > > > > > > > > store i64 ptrtoint (ptr getelementptr (ptr, ptr null, i32 1)
> > > > > > > > > to i64), ptr %11, align 8
> > > > > > > > > ...
> > > > > > > > > %14 = getelementptr inbounds [4 x i64], ptr %4, i32 0, i32 1
> > > > > > > > > store i64 ptrtoint (ptr getelementptr (ptr, ptr null, i32 1)
> > > > > > > > > to i64), ptr %14, align 8
> > > > > > > > > ...
> > > > > > > > > %17 = getelementptr inbounds [4 x i64], ptr %4, i32 0, i32 2
> > > > > > > > > store i64 ptrtoint (ptr getelementptr (ptr, ptr null, i32 1)
> > > > > > > > > to i64), ptr %17, align 8
> > > > > > > > > ...
> > > > > > > > > %20 = getelementptr inbounds [4 x i64], ptr %4, i32 0, i32 3
> > > > > > > > > store i64 ptrtoint (ptr getelementptr (ptr, ptr null, i32 1)
> > > > > > > > > to i64), ptr %20, align 8
> > > > > > > > > ...
> > > > > > > > > %23 = getelementptr inbounds [4 x i64], ptr %4, i32 0, i32 0
> > > > > > > > > call void @__tgt_target_data_begin_mapper(ptr @5, i64 -1, i32
> > > > > > > > > 4, ptr %21, ptr %22, ptr %23, ptr @.offload_maptypes, ptr
> > > > > > > > > @.offload_mapnames, ptr null)
> > > > > > > > > ```
> > > > > > > > >
> > > > > > > > > I would like some more clarity on this before proceeding.
> > > > > > > > > Clang generates different code for this and I see that it is
> > > > > > > > > appropriately filling the `ArgSizes` field.
> > > > > > > > `OpenMPIRBuilder::getSizeInBytes` is the function responsible
> > > > > > > > for calculating the `ArgSizes`.
> > > > > > > >
> > > > > > > > For the Value : `%1 = alloca i64, i64 1, align 8` it returns
> > > > > > > > size as `i64 ptrtoint (ptr getelementptr (ptr, ptr null, i32 1)
> > > > > > > > to i64)` and TBH I don't understand this. This function was
> > > > > > > > taken from OpenACC.
> > > > > > > >
> > > > > > > > I will re-implement this function and update the patch.
> > > > > > > Actually, the generated code seems correct. The first answer [[
> > > > > > > https://stackoverflow.com/questions/14608250/how-can-i-find-the-size-of-a-type
> > > > > > > | here ]] gives insight into how
> > > > > > > `OpenMPIRBuilder::getSizeInBytes` is calculating the size of the
> > > > > > > type.
> > > > > > >
> > > > > > > Opaque pointers make it look the same for all the different
> > > > > > > types, disabling opaque pointers you get something like the
> > > > > > > following:
> > > > > > >
> > > > > > > `integer(8) :: a` :
> > > > > > > ```
> > > > > > > %7 = getelementptr inbounds [1 x i64], [1 x i64]*
> > > > > > > %.offload_sizes, i32 0, i32 0
> > > > > > > store i64 ptrtoint (i64** getelementptr (i64*, i64** null, i32
> > > > > > > 1) to i64), i64* %7, align 4
> > > > > > > ```
> > > > > > >
> > > > > > > `integer :: b(1024)` :
> > > > > > >
> > > > > > > ```
> > > > > > > %8 = getelementptr inbounds [1 x i64], [1 x i64]*
> > > > > > > %.offload_sizes, i32 0, i32 0
> > > > > > > store i64 ptrtoint ([1024 x i32]** getelementptr ([1024 x
> > > > > > > i32]*, [1024 x i32]** null, i32 1) to i64), i64* %8, align 4
> > > > > > > ```
> > > > > > >
> > > > > > > Let me know if this makes sense.
> > > > > > >
> > > > > > > Thanks,
> > > > > > > Akash
> > > > > > Ahh OK. It does make it a bit harder to read.
> > > > > >
> > > > > > But going to back to my general question:
> > > > > > ```
> > > > > > In general how are you passing the size of the fortran
> > > > > > variable/type to the OpenMP runtime? For scalars and arrays with
> > > > > > sizes known at compile time, this comes from the type itself. But
> > > > > > for other types like assumed-shape arrays, variable length arrays
> > > > > > this information comes from the descriptor or from other fields. My
> > > > > > question is how is this being collected and passed to the runtime
> > > > > > ```
> > > > > >
> > > > > > Consider the following two subroutines, It has two assumed shape
> > > > > > arrays. In sb0 it is a rank-1 array, in sb1 it is a rank-2 array.
> > > > > > At the llvm dialect layer, these two will be represented by struct
> > > > > > equivalents of Fortran descriptors as given below. If we now find
> > > > > > the size of the types, it would get the size of the descriptor
> > > > > > struct rather than it memory it is referring to. I guess this is
> > > > > > not what we want to do. I believe this would require some special
> > > > > > processing, unless the patch also does something for this.
> > > > > >
> > > > > > ```
> > > > > > omp.target_data map((to -> %arg0 : !llvm.ptr<struct<(ptr<i32>,
> > > > > > i64, i32, i8, i8, i8, i8, array<1 x array<3 x i64>>)>>))
> > > > > > ```
> > > > > >
> > > > > > ```
> > > > > > omp.target_data map((to -> %arg0 : !llvm.ptr<struct<(ptr<i32>,
> > > > > > i64, i32, i8, i8, i8, i8, array<1 x array<3 x i64>>)>>))
> > > > > > ```
> > > > > >
> > > > > >
> > > > > > ```
> > > > > > subroutine sb0(a)
> > > > > > integer :: a(:)
> > > > > > !$omp target data map(to: a)
> > > > > > a(10) = 20
> > > > > > !$omp end target data
> > > > > > end subroutine
> > > > > >
> > > > > > subroutine sb1(a)
> > > > > > integer :: a(:,:)
> > > > > > !$omp target data map(to: a)
> > > > > > a(5,6) = 20
> > > > > > !$omp end target data
> > > > > > end subroutine
> > > > > > ```
> > > > > Just want to clarify that I am not expecting a fix here. But just a
> > > > > statement about what is supported and what is not supported.
> > > > In line 1382 you can see how the size is determined. It is done simply
> > > > by passing the map variable to the `getSizeInBytes` function.
> > > >
> > > > I haven't added any special handling for assumed-shape arrays or any
> > > > other special cases. I am not sure if it is equivalent to an `int*` in
> > > > C, but looking at the llvm IR, if the map variable is an `i32*` then
> > > > clang sets the size to 4, and for assumed-shape arrays in your examples
> > > > `sb0` and `sb1` it also creates `i32*` in the llvm IR and the size for
> > > > these calculated in the same way.
> > > >
> > > > I am not sure if this is the correct behaviour. Do you know what is the
> > > > correct size that should be passed in your examples to the runtime? If
> > > > it is relatively straightforward then I can look into adding support
> > > > for these, otherwise maybe we can add a TODO for handling assumed-shape
> > > > arrays in a future patch.
> > > Sorry, made a mistake in previous comment.
> > >
> > > Clang sets size to 8 and not 4 for `i32*`.
> > Also, the standard specifies `assumed`-size arrays are not supported. I am
> > not sure if the arrays in your example are assumed-shape or assumed-size.
> They are assumed-shape arrays.
>
> We are probably missing a semantic check for the assumed-size case. But good
> to know that they need not be supported. In one of the examples, you
> provided, it was mentioned to be supported. If you can create a ticket for
> this that would be great. Gfortran catches this error.
> ```
> subroutine openmp_target_data_region(a)
> real :: a(*)
> !$omp target enter data map(to: a)
> end subroutine openmp_target_data_region
> ```
>
> In general, besides assumed-shape, there are various cases where a descriptor
> can come in. Like for pointers and allocatable arrays.
> ```
> subroutine sb4
> integer, pointer :: a(:)
> allocate(a(10))
> !$omp target data map(to: a)
> a(10) = 20
> !$omp end target data
> end subroutine
> ```
>
> For array sections:
> ```
> subroutine sb4
> integer :: a(10)
> !$omp target data map(to: a(3:10))
> a(10) = 20
> !$omp end target data
> end subroutine
> ```
>
> I believe the size should be passed to the runtime, then only it can compute
> how many bytes should be mapped.
>
> From your answers,
> 1. The following types are supported:
> scalars, constant sized arrays
> 2. The following types are probably supported:
> variable length arrays, derived types with elements of type in (1) or (2)
> 3. The following types are not supported:
> assumed-size arrays, pointers, allocatables, derived type with elements of
> type in (3), array-sections (this segfaults now).
>
> Would it be OK to add types in (2) and (3) as TODO failures in `flang`?
I've added the TODO. Please let me know if I missed any scenario there.
Thanks :)
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