International Business Machines Corporation

Wolfram M Sauer

David S Levitan

Samuel Jonathan Thomas

Brian R Konigsburg

Ravi Nair

Dieter F Wendel

Lee Evan Eisen

Petra Leber

Jens Leenstra

Francis Patrick O'Connell

Charles Roberts Moore

Rolf B Hilgendorf

Hartmut R Schwermer

Methods for storing branch information in an address table of a processor are disclosed. A processor of the disclosed embodiments may generally include an instruction fetch unit connected to an instruction cache, a branch execution unit, and an address table being connected to the instruction fetch unit and the branch execution unit. The address table may generally be adapted to store a plurality of entries with each entry of the address table being adapted to store a base address and a base instruction tag. In a further embodiment, the branch execution unit may be adapted to determine the address of a branch instruction having an instruction tag based on the base address and the base instruction tag of an entry of the address table associated with the instruction tag. In some embodiments, the address table may further be adapted to store branch information.

Storing branch information in an address table of a processor

A method and logical apparatus for managing processing system resource use for speculative execution reduces the power and performance burden associated with inefficient speculative execution of program instructions. A measure of the efficiency of speculative execution is used to reduce resources allocated to a thread while the speculation efficiency is low. The resource control applied may be the number of instruction fetches allocated to the thread or the number of execution time slices. Alternatively, or in combination, the size of a prefetch instruction storage allocated to the thread may be limited. The control condition may be comparison of the number of correct or incorrect speculations to a threshold, comparison of the number of correct to incorrect speculations, or a more complex evaluator such as the size of a ratio of incorrect to total speculations.

Method and logical apparatus for managing processing system resource use for speculative execution

Methods and systems for storing branch information in an address table of a processor are disclosed. A processor of the disclosed embodiments may generally include an instruction fetch unit connected to an instruction cache, a branch execution unit, and an address table being connected to the instruction fetch unit and the branch execution unit. The address table may generally be adapted to store a plurality of entries with each entry of the address table being adapted to store a base address and a base instruction tag. In a further embodiment, the branch execution unit may be adapted to determine the address of a branch instruction having an instruction tag based on the base address and the base instruction tag of an entry of the address table associated with the instruction tag. In some embodiments, the address table may further be adapted to store branch information.

Methods and systems for storing branch information in an address table of a processor

A method for operating a processor having an architecture of a larger bitlength with a program comprising instructions compiled to produce instruction results of at least one smaller bitlength having the steps of detecting when in program order a first smaller bitlength instruction is to be dispatched which does not have a target register address as one of its sources, and adding a so_extract_instruction into an instruction stream before the smaller bitlength instruction. The extract instruction includes the steps of dispatching the extract instruction together with the following smaller bitlength instruction from an instruction queue into a Reservation Station, issuing the extract instruction to an Instruction Execution Unit (IEU) as soon as all source operand data is available and an IEU is available according to respective issue scheme, executing the extract instruction by an available IEU, setting an indication that the result of the instruction needs to be written into the result field of the instruction following the extract instruction, and writing the extract instruction result into the result field of the first instruction, and into all fields of operands being dependent of the first instruction.

Method for handling 32 bit results for an out-of-order processor with a 64 bit architecture

A Storage Reference Buffer (SRB) designed as an autonomous unit for all Store operations that transfer data from the execution unit of a processor to the memory hierarchy and Load operations that transfer data from the memory hierarchy to the execution unit of the processor. The SRB partitions up the Load and Store operations into several smaller operations in order to perform them in parallel with other Load and Store requests. System elements are included to determine unambiguously which of these Load and Store operations may be performed without waiting for prior operations to be completed. The SRB also includes system elements to detect whether requests may be satisfied by existing entries in the SRB without having to access the cache. The SRB is operated as a content addressable memory. Load request are simultaneously launched to cache and to the SRB with the Cache request being canceled if the Load request may be satisfied by an SRB entry.

Managing load and store operations using a storage management unit with data flow architecture

A method for addressing internal instructions in an out-of-order processor is proposed, which allows for an efficient register renaming even in case internal instructions are issued to a multitude of window buffers. In this case, it is not clear how internal instructions that stem from one external instruction can be indicated as being 'related'. In the method proposed, a common instruction identifier is assigned to each of the internal instructions of a group of internal instructions representing an external instruction. Furtheron, an offset identifier is assigned to each of said internal instructions in order to be able to unambiguously identify each of said internal instructions. These two identifiers are used as a tag, in order to be able to resolve data dependencies. By use of the invention, exception handling, recovery of mispredicted branches, and committing related instructions corresponding to one external instruction is simplified.

Growing community of inventors

Nufringen, Germany

Wolfram M Sauer