International Business Machines Corporation

Daniel Lipetz

James J Bonanno

Adam B Collura

Brian Robert Prasky

Michael J Cadigan, Jr

Anthony Saporito

Steven R Carlough

Matthias D Heizmann

Silvia Melitta Mueller

Petra Leber

Patrick James Meaney

Bruce Martin Fleischer

Craig Raymond Walters

Steven J Hnatko

Joshua M Weinberg

Christian Jacobi

Eric M Schwarz

Ashutosh Misra

Mark Alan Erle

A system includes a branch predictor and a processing circuit configured to perform a plurality of operations including storing a skip-over offset value in the branch predictor. The skip-over offset value defines a number of search addresses of the branch predictor to be skipped. The operations further include searching the branch predictor for a branch prediction. Responsive to finding the branch prediction, the searching of the branch predictor is re-indexed based on the skip-over offset value associated with the branch prediction.

Skip-over offset branch prediction

A computer system includes a branch detection module and a branch predictor module. The branch detection module determines that a first program branch is a possible call branch having a next sequential instruction address (NSIA), and determines that a first routine branch is a possible return capable branch having the first routine instruction address that is a detected as being offset. The branch predictor module determines that a second program branch is a possible call branch having a next sequential instruction address (NSIA), and determines that a second routine branch is a predicted return branch having a predicted target instruction address based on the NSIA of the second program branch and the predicted offset.

Call/return stack branch target predictor to multiple next sequential instruction addresses

In an approach for protecting recoding logic in a computing environment, a processor obtains an operand of an instruction in a first data format. A processor converts the operand from the first data format to a second data format. A processor generates a predicted residue of the operand in the second data format, wherein generating the predicted residue of the operand in the second data format comprises: generating a residue of the operand from the first data format.

Residue prediction of packed data

Examples of techniques for distance-based branch prediction are disclosed. In one example implementation according to aspects of the present disclosure, a computer-implemented method includes: determining, by a processing system, a potential return instruction address (IA) by determining whether a relationship is satisfied between a first target IA and a first branch IA; storing a second branch IA as a return when a target IA of a second branch matches a potential return IA for the second branch; and applying the potential return IA for the second branch as a predicted target IA of a predicted branch IA stored as a return.

Distance based branch prediction and detection of potential call and potential return instructions

Embodiments are directed to a method for optimizing performance of a microprocessor. The method includes monitoring the performance of the microprocessor in each of a plurality of performance modes. The method further includes choosing a performance mode based on the monitoring. Thereafter, using the performance mode for a predetermined amount of time. Each of the plurality of performance modes is a branch prediction mode.

Heuristic method to control fetching of metadata from a cache hierarchy

Embodiments relate to branch prediction using a pattern history table (PHT) that is indexed using a global path vector (GPV). An aspect includes receiving a search address by a branch prediction logic that is in communication with the PHT and the GPV. Another aspect includes starting with the search address, simultaneously determining a plurality of branch predictions by the branch prediction logic based on the PHT, wherein the plurality of branch predictions comprises one of: (i) at least one not taken prediction and a single taken prediction, and (ii) a plurality of not taken predictions. Another aspect includes updating the GPV by shifting an instruction identifier of a branch instruction associated with a taken prediction into the GPV, wherein the GPV is not updated based on any not taken prediction.

Branch prediction using multi-way pattern history table (PHT) and global path vector (GPV)

A method, system, and computer program product of utilizing branch prediction logic in a system that processes instructions that include a branch are described. The method includes identifying the branch as conventionally predictable or not conventionally predictable, and based on the branch being identified as not conventionally predictable according to the identifying, either foregoing branch prediction and reallocating, using a processor, the branch prediction logic to another thread of the instructions or performing, using the processor, the branch prediction and speculative execution of one or more of the instructions following the branch to obtain prediction information. Based on the performing the branch prediction and the speculative execution, the method also includes verifying a match between a branch end according to the instructions and a branch end according to the branch prediction prior to providing the prediction information to a second processor processing the instructions.

Silent mode and resource reassignment in branch prediction logic

A computer-implemented method for predicting a taken branch that ends an instruction stream in a pipelined high frequency microprocessor includes receiving, by a processor, a first instruction within a first instruction stream, the first instruction including a first instruction address. The computer-implemented method further includes searching, by the processor, a stream-based index accelerator predictor one time for the stream; determining, by the processor, a prediction for a branch ending the branch stream; influencing, by the processor, a metadata prediction engine based on the prediction; and updating, by the processor, a stream-based index accelerator predictor with information indicative of the prediction.

Stream based branch prediction index accelerator with power prediction

A computer-implemented method for predicting a taken branch that ends an instruction stream in a pipelined high frequency microprocessor includes receiving, by a processor, a first instruction within a first instruction stream, the first instruction comprising a first instruction address; searching, by the processor, an index accelerator predictor one time for the stream; determining, by the processor, a prediction for a taken branch ending the branch stream; influencing, by the processor, a metadata prediction engine based on the prediction; observing a plurality of taken branches from the exit accelerator predictor; maintaining frequency information based on the observed taken branches; determining, based on the frequency information, an updated prediction of the observed plurality of taken branches; and updating, by the processor, the index accelerator predictor with the updated prediction.

Stream based branch prediction index accelerator for multiple stream exits

A computer-implemented method for predicting a taken branch that ends an instruction stream in a pipelined high frequency microprocessor includes receiving, by a processor, a first instruction within a first instruction stream, the first instruction comprising a first instruction address; searching, by the processor, an index accelerator predictor one time for the stream; determining, by the processor, a prediction for a taken branch ending the branch stream; influencing, by the processor, a metadata prediction engine based on the prediction; observing a plurality of taken branches from the exit accelerator predictor; maintaining frequency information based on the observed taken branches; determining, based on the frequency information, an updated prediction of the observed plurality of taken branches; and updating, by the processor, the index accelerator predictor with the the updated prediction.

A computer-implemented method includes determining, by a stream-based index accelerator predictor of a processor, a predicted stream length between an instruction address and a taken branch ending an instruction stream. A first-level branch predictor of a hierarchical asynchronous lookahead branch predictor of the processor is searched for a branch prediction in one or more entries in a search range bounded by the instruction address and the predicted stream length. A search of a second-level branch predictor of the hierarchical asynchronous lookahead branch predictor is triggered based on failing to locate the branch prediction in the search range.

Branch predictor search qualification using stream length prediction

Scheduling memory accesses in a memory system having a multiple ranks of memory, at most r ranks of which may be powered up concurrently, in which r is less than the number of ranks. If fewer than r ranks are powered up, a subset of requested powered down ranks is powered up, such that at r ranks are powered up, the subset of requested powered down ranks to be powered up including the most frequently accessed requested powered down ranks. Then, if fewer than r ranks are powered up, a subset of unrequested powered down ranks is powered up, such that a total of at most r ranks is powered up concurrently, the subset of unrequested powered down ranks to be powered up including the most frequently accessed unrequested powered down ranks.

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Linden, NJ, United States of America

Daniel Lipetz