Reland "[flang] Inline hlfir.dot_product. (llvm#123143)"

This reverts commit afc43a7.
+Fixed declaration of hlfir::genExtentsVector().

Author: vzakhari

flang/include/flang/Optimizer/Builder/HLFIRTools.h

@@ -513,6 +513,12 @@ genTypeAndKindConvert(mlir::Location loc, fir::FirOpBuilder &builder,
 Entity loadElementAt(mlir::Location loc, fir::FirOpBuilder &builder,
                      Entity entity, mlir::ValueRange oneBasedIndices);
 
+/// Return a vector of extents for the given entity.
+/// The function creates new operations, but tries to clean-up
+/// after itself.
+llvm::SmallVector<mlir::Value, Fortran::common::maxRank>
+genExtentsVector(mlir::Location loc, fir::FirOpBuilder &builder, Entity entity);
+
 } // namespace hlfir
 
 #endif // FORTRAN_OPTIMIZER_BUILDER_HLFIRTOOLS_H

flang/lib/Optimizer/Builder/HLFIRTools.cpp

@@ -1421,3 +1421,15 @@ hlfir::Entity hlfir::loadElementAt(mlir::Location loc,
   return loadTrivialScalar(loc, builder,
                            getElementAt(loc, builder, entity, oneBasedIndices));
 }
+
+llvm::SmallVector<mlir::Value, Fortran::common::maxRank>
+hlfir::genExtentsVector(mlir::Location loc, fir::FirOpBuilder &builder,
+                        hlfir::Entity entity) {
+  entity = hlfir::derefPointersAndAllocatables(loc, builder, entity);
+  mlir::Value shape = hlfir::genShape(loc, builder, entity);
+  llvm::SmallVector<mlir::Value, Fortran::common::maxRank> extents =
+      hlfir::getExplicitExtentsFromShape(shape, builder);
+  if (shape.getUses().empty())
+    shape.getDefiningOp()->erase();
+  return extents;
+}