[Openmp-commits] [openmp] [Flang][OpenMP][MLIR] Initial array section mapping MLIR -> LLVM-IR lowering utilising omp.bounds (PR #68689)

[via Openmp-commits]

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@@ -1629,13 +1622,153 @@ getRefPtrIfDeclareTarget(mlir::Value value,
   return nullptr;
 }
 
+// A small helper structure to contain data gathered
+// for map lowering and coalese it into one area and
+// avoiding extra computations such as searches in the
+// llvm module for lowered mapped varibles or checking
+// if something is declare target (and retrieving the
+// value).
+struct MapData {
+  bool isDeclareTarget = false;
+  mlir::Operation *mapClause;
+  llvm::Value *basePointer;
+  llvm::Value *pointer;
+  llvm::Value *kernelValue;
+  llvm::Type *underlyingType;
+  llvm::Value *sizeInBytes;
+};
+
+uint64_t getArrayElementSizeInBits(LLVM::LLVMArrayType arrTy, DataLayout &dl) {
+  if (auto nestedArrTy = llvm::dyn_cast_if_present<LLVM::LLVMArrayType>(
+          arrTy.getElementType()))
+    return getArrayElementSizeInBits(nestedArrTy, dl);
+  return dl.getTypeSizeInBits(arrTy.getElementType());
+}
+
+// This function calculates the size to be offloaded for a specified type, given
+// its associated map clause (which can contain bounds information which affects
+// the total size), this size is calculated based on the underlying element type
+// e.g. given a 1-D array of ints, we will calculate the size from the integer
+// type * number of elements in the array. This size can be used in other
+// calculations but is ultimately used as an argument to the OpenMP runtimes
+// kernel argument structure which is generated through the combinedInfo data
+// structures.
+// This function is somewhat equivalent to Clang's getExprTypeSize inside of
+// CGOpenMPRuntime.cpp.
+llvm::Value *getSizeInBytes(DataLayout &dl, const mlir::Type &type,
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agozillon wrote:

I'd prefer to always utilise the bounds as it makes calculating these trivial for all scenarios (fixed/ assumed shape / assumed size). Although, it is a shame we are re-computing the value in this case. I am fine with either method we choose though, so I'll leave it up to reviewers. There's a fairly length discussion relating to this topic here: https://github.com/llvm/llvm-project/pull/67164 

Please do let me know which direction the reviewers wish to go so the patch can progress! 

https://github.com/llvm/llvm-project/pull/68689