set aside fixnums in GCL
Major Section:  ACL2-BUILT-INS

(Allocate-fixnum-range fixnum-lo fixnum-hi) causes Gnu Common Lisp (GCL) to create a persistent table for the integers between fixnum-lo and fixnum-hi (both bounds inclusive). This table is referenced first when any integer is boxed and the existing box in the table is used if the integer is in bounds. This can speed up GCL considerably by avoiding wasteful fixnum boxing. Here, fixnum-lo and fixnum-hi should be fixnums, more specifically of type (signed-byte 30), with fixnum-lo <= fixnum-hi.

When this function is executed in a Lisp implementation other than GCL, it has no side effect. This function always returns nil.