[PATCH] D142914: [MLIR][OpenMP] Added OMPIRBuilder support for Target Data directives.
Akash Banerjee via Phabricator via cfe-commits
cfe-commits at lists.llvm.org
Thu Mar 9 06:07:20 PST 2023
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,
----------------
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
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D142914/new/
https://reviews.llvm.org/D142914
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