Michael T O'Connor

US Patent:

61015806, Aug 8, 2000

Filed:

Apr 23, 1997

Appl. No.:

8/838971

Inventors:

Ole Agesen - Franklin MA
Steve Heller - Chelmsford MA
Michael O'Connor - Union City CA
Guy Steele - Lexington MA
Marc Tremblay - Palo Alto CA

Assignee:

Sun Microsystems, Inc. - Palo Alto CA

International Classification:

G06F 1208

US Classification:

711132

Abstract:

In computer systems which do not inherently distinguish between references and primitive values within a program stack a method and apparatus to assist exact garbage collection techniques utilizes a stack tag cache which operates in conjunction with a program stack and supplies a tag item for every entry in the process stack. The value of a tag item indicates whether the stack entry is either a reference to another memory location or a primitive value, i. e. integer or floating point number. The arrangements and values of the tag items are correlated with changes to the program stack. The stack tag cache includes facilities for swapping the contents of the cache in the event of a trap or context switch, as well as means for redundantly verifying the tag value with intended instruction operand types.