Subroutine return through branch history table
US5276882A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 27, 1990 |
| Grant date | Jan 4, 1994 |
| Priority date | — |
| Expiry date | Jul 27, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F9/4486
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
Method and apparatus for correctly predicting an outcome of a branch instruction in a system of the type that includes a Branch History Table (BHT) and branch instructions that implement non-explicit subroutine calls and returns. Entries in the BHT have two additional stage fields including a CALL field to indicate that the branch entry corresponds to a branch that may implement a subroutine call and a PSEUDO field. The PSEUDO field represents linkage information and creates a link between a subroutine entry and a subroutine return. A target address of a successful branch instruction is used to search the BHT. The branch is known to be a subroutine return if a target quadword contains an entry prior to a target halfword that has the CALL field set. The entry with the CALL bit set is thus known to be the corresponding subroutine call, and the entry point to the subroutine is given by the target address stored within the entry. A PSEUDO entry is inserted into the BHT at the location corresponding to the entry point of the subroutine, the PSEUDO entry being designated as such by having the PSEUDO field asserted. The PSEUDO entry contains the address of the returning branch instruction…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.