Store the size of the outermost dimension in case of newly created arrays that...

Store the size of the outermost dimension in case of newly created arrays that require memory allocation.

We do not need the size of the outermost dimension in most cases, but if we
allocate memory for newly created arrays, that size is needed.

Reviewed-by: Michael Kruse <llvm@meinersbur.de>

Differential Revision: https://reviews.llvm.org/D23991

llvm-svn: 281234