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

[Kiran Chandramohan]

================
@@ -1642,13 +1635,154 @@ 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) more than neccessary.
+struct MapInfoData : llvm::OpenMPIRBuilder::MapInfosTy {
+  llvm::SmallVector<bool, 4> IsDeclareTarget;
+  llvm::SmallVector<mlir::Operation *, 4> MapClause;
+  llvm::SmallVector<llvm::Value *, 4> OriginalValue;
+  // Stripped off array/pointer to get the underlying
+  // element type
+  llvm::SmallVector<llvm::Type *, 4> BaseType;
+
+  /// Append arrays in \a CurInfo.
+  void append(MapInfoData &CurInfo) {
+    IsDeclareTarget.append(CurInfo.IsDeclareTarget.begin(),
+                           CurInfo.IsDeclareTarget.end());
+    MapClause.append(CurInfo.MapClause.begin(), CurInfo.MapClause.end());
+    OriginalValue.append(CurInfo.OriginalValue.begin(),
+                         CurInfo.OriginalValue.end());
+    BaseType.append(CurInfo.BaseType.begin(), CurInfo.BaseType.end());
+    llvm::OpenMPIRBuilder::MapInfosTy::append(CurInfo);
+  }
+};
+
+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,
+                            Operation *clauseOp, llvm::IRBuilderBase &builder,
+                            LLVM::ModuleTranslation &moduleTranslation) {
+  // utilising getTypeSizeInBits instead of getTypeSize as getTypeSize gives
+  // the size in inconsistent byte or bit format.
+  uint64_t underlyingTypeSzInBits = dl.getTypeSizeInBits(type);
+  if (auto arrTy = llvm::dyn_cast_if_present<LLVM::LLVMArrayType>(type)) {
+    underlyingTypeSzInBits = getArrayElementSizeInBits(arrTy, dl);
+  }
+
+  if (auto memberClause =
+          mlir::dyn_cast_if_present<mlir::omp::MapInfoOp>(clauseOp)) {
+    // This calculates the size to transfer based on bounds and the underlying
+    // element type, provided bounds have been specified (Fortran
+    // pointers/allocatables/target and arrays that have sections specified fall
+    // into this as well).
+    if (!memberClause.getBounds().empty()) {
+      llvm::Value *elementCount = builder.getInt64(1);
+      for (auto bounds : memberClause.getBounds()) {
+        if (auto boundOp = mlir::dyn_cast_if_present<mlir::omp::DataBoundsOp>(
+                bounds.getDefiningOp())) {
+          // The below calculation for the size to be mapped calculated from the
+          // map_info's bounds is: (elemCount * [UB - LB] + 1), later we
+          // multiply by the underlying element types byte size to get the full
+          // size to be offloaded based on the bounds
+          elementCount = builder.CreateMul(
+              elementCount,
+              builder.CreateAdd(
+                  builder.CreateSub(
+                      moduleTranslation.lookupValue(boundOp.getUpperBound()),
+                      moduleTranslation.lookupValue(boundOp.getLowerBound())),
+                  builder.getInt64(1)));
+        }
+      }
+
+      // The size in bytes x number of elements, the sizeInBytes stored is
+      // the underyling types size, e.g. if ptr<i32>, it'll be the i32's
+      // size, so we do some on the fly runtime math to get the size in
+      // bytes from the extent (ub - lb) * sizeInBytes. NOTE: This may need
+      // some adjustment for members with more complex types.
+      return builder.CreateMul(elementCount,
+                               builder.getInt64(underlyingTypeSzInBits / 8));
+    }
+  }
+
+  return builder.getInt64(underlyingTypeSzInBits / 8);
+}
+
+// Get the underlying LLVM type, this will bypass the pointer and
+// access the underlying type. Which bypasses llvm's opaque pointers
+// to get the underlying type via MLIR.
+llvm::Type *getLLVMIRType(mlir::Type inputType,
+                          LLVM::ModuleTranslation &moduleTranslation) {
+  llvm::Type *type = moduleTranslation.convertType(inputType);
+  if (auto pointerType =
+          llvm::dyn_cast<mlir::omp::PointerLikeType>(inputType)) {
+    if (auto eleType = pointerType.getElementType()) {
----------------
kiranchandramohan wrote:

This will stop working after the `opaque pointer` switch for the llvm dialect. We should not be using the `getElementType` here. Can we get this from `varType` field of `MapInfo` ?

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