Abstract: Methods and apparatus relating to branch prefetch mechanisms for mitigating front-end branch resteers are described. In an embodiment, predecodes an entry in a cache to generate a predecoded branch operation. The entry is associated with a cold branch operation, where the cold branch operation corresponds to an operation that is detected for a first time after storage in an instruction cache and wherein the cold branch operation remains undecoded since it is stored at a location in a cache line prior to a subsequent location of a branch operation in the cache line. The predecoded branch operation is stored in a Branch Prefetch Buffer (BPB) in response to a cache line fill operation of the cold branch operation in an instruction cache. Other embodiments are also disclosed and claimed.

Abstract: In an embodiment, a processor includes a branch prediction circuit and a plurality of processing engines. The branch prediction circuit is to: detect a coherence operation associated with a first memory address; identify a first branch instruction associated with the first memory address; and predict a direction for the identified branch instruction based on the detected coherence operation. Other embodiments are described and claimed.

Abstract: Techniques for selective disable of history-based predictors on mode transitions are described. An example apparatus comprises first circuitry to provide a history-based prediction, and second circuitry coupled to the first circuitry to selectively block and unblock a prediction from the first circuitry after a mode transition. Other examples are disclosed and claimed.

Abstract: Techniques and mechanisms for a processor to determine an execution of instructions based on a prediction of a taken branch. In an embodiment, a first prediction unit generates each of multiple branch predictions in one cycle of successive branch prediction cycles. An indication of the branch predictions is provided to an execution pipeline, which prepares to execute an instruction based on the indication. Where a first one of the branch predictions is determined to be of a low confidence type, said first branch prediction is further indicated to a second prediction unit, which performs a second branch prediction based on the same branch instruction for which the first branch prediction was made. In another embodiment, the second prediction unit signals that a state of the execution pipeline is to be cleared, based on a determination that the first and second branch predictions are inconsistent with each other.

Abstract: An apparatus and method for a speculative conditional move instruction. A processor comprising: a decoder to decode a first speculative conditional move instruction; a prediction storage to store prediction data related to previously executed speculative conditional move instructions; and execution circuitry to read first prediction data associated with the speculative conditional move instruction and to execute the speculative conditional move instruction either speculatively or non-speculatively based on the first prediction data.

Abstract: Disclosed embodiments relate to systems and methods structured to predict a loop exit. In one example, a processor includes a branch prediction unit to determine a loop exit predictor start corresponding to a finite consistent loop, and an instruction decoder queue to: receive an iteration of the finite consistent loop corresponding to a loop exit predictor and an iteration count, replay one or more instructions of the iteration based on the iteration count, and switch to post-loop instructions responsive to a determination that a number of iterations of the finite consistent loop is equal to the iteration count.

Abstract: Disclosed embodiments relate to the usage of a branch prediction unit in service of performance sensitive microcode flows. In one example, a processor includes a branch prediction unit (BPU) and a pipeline including a fetch stage to fetch an instruction specifying an opcode, an operand, and a loop condition based on the operand, wherein the BPU is to generate a hint reflecting a predicted result of the loop condition, a decode stage to generate either a first or a second micro-operation flow as per the hint, the pipeline to begin executing the generated micro-operation flow; a read stage to read the operand and resolve the loop condition; and execution circuitry to continue the generated micro-operation flow if the prediction was correct, and, otherwise, to flush the pipeline, update the prediction, and switch from the generated micro-operation flow to the other of the first and second micro-operation flows.

Abstract: In one embodiment, an apparatus includes a context-based prediction circuit to receive an instruction address for a branch instruction and a plurality of predictions associated with the branch instruction from a global prediction circuit. The context-based prediction circuit may include: a table having a plurality of entries each to store a context prediction value for a corresponding branch instruction; and a control circuit to generate, for the branch instruction, an index value to index into the table, the control circuit to generate the index value based at least in part on at least some of the plurality of predictions associated with the branch instruction and the instruction address for the branch instruction. Other embodiments are described and claimed.

Abstract: Disclosed embodiments relate to the usage of a branch prediction unit in service of performance sensitive microcode flows. In one example, a processor includes a branch prediction unit (BPU) and a pipeline including a fetch stage to fetch an instruction specifying an opcode, an operand, and a loop condition based on the operand, wherein the BPU is to generate a hint reflecting a predicted result of the loop condition, a decode stage to generate either a first or a second micro-operation flow as per the hint, the pipeline to begin executing the generated micro-operation flow; a read stage to read the operand and resolve the loop condition; and execution circuitry to continue the generated micro-operation flow if the prediction was correct, and, otherwise, to flush the pipeline, update the prediction, and switch from the generated micro-operation flow to the other of the first and second micro-operation flows.

Abstract: An apparatus and method for a speculative conditional move instruction. A processor comprising: a decoder to decode a first speculative conditional move instruction; a prediction storage to store prediction data related to previously executed speculative conditional move instructions; and execution circuitry to read first prediction data associated with the speculative conditional move instruction and to execute the speculative conditional move instruction either speculatively or non-speculatively based on the first prediction data.

Abstract: In one embodiment, an apparatus includes a context-based prediction circuit to receive an instruction address for a branch instruction and a plurality of predictions associated with the branch instruction from a global prediction circuit. The context-based prediction circuit may include: a table having a plurality of entries each to store a context prediction value for a corresponding branch instruction; and a control circuit to generate, for the branch instruction, an index value to index into the table, the control circuit to generate the index value based at least in part on at least some of the plurality of predictions associated with the branch instruction and the instruction address for the branch instruction. Other embodiments are described and claimed.

Abstract: An apparatus and method for a speculative conditional move instruction. A processor comprising: a decoder to decode a first speculative conditional move instruction; a prediction storage to store prediction data related to previously executed speculative conditional move instructions; and execution circuitry to read first prediction data associated with the speculative conditional move instruction and to execute the speculative conditional move instruction either speculatively or non-speculatively based on the first prediction data.

Abstract: In an embodiment, a processor includes a branch prediction circuit and a plurality of processing engines. The branch prediction circuit is to: detect a coherence operation associated with a first memory address; identify a first branch instruction associated with the first memory address; and predict a direction for the identified branch instruction based on the detected coherence operation. Other embodiments are described and claimed.

Abstract: A processor includes a processor core and a micro-op cache communicably coupled to the processor core. The micro-op cache includes a micro-op tag array, wherein tag array entries in the micro-op tag array are indexed according to set and way of set-associative cache, and a micro-op data array to store multiple micro-ops. The data array entries in the micro-op data array are indexed according to bank number of a plurality of cache banks and to a set within one cache bank of the plurality of cache banks.

Abstract: In an embodiment, a processor includes a branch prediction circuit and a plurality of processing engines. The branch prediction circuit is to: detect a coherence operation associated with a first memory address; identify a first branch instruction associated with the first memory address; and predict a direction for the identified branch instruction based on the detected coherence operation. Other embodiments are described and claimed.

Abstract: An apparatus and method for a speculative conditional move instruction. A processor comprising: a decoder to decode a first speculative conditional move instruction; a prediction storage to store prediction data related to previously executed speculative conditional move instructions; and execution circuitry to read first prediction data associated with the speculative conditional move instruction and to execute the speculative conditional move instruction either speculatively or non-speculatively based on the first prediction data.

Abstract: In an embodiment, a processor includes a branch prediction circuit and a plurality of processing engines. The branch prediction circuit is to: detect a coherence operation associated with a first memory address; identify a first branch instruction associated with the first memory address; and predict a direction for the identified branch instruction based on the detected coherence operation. Other embodiments are described and claimed.

Abstract: A processor includes a processor core and a micro-op cache communicably coupled to the processor core. The micro-op cache includes a micro-op tag array, wherein tag array entries in the micro-op tag array are indexed according to set and way of set-associative cache, and a micro-op data array to store multiple micro-ops. The data array entries in the micro-op data array are indexed according to bank number of a plurality of cache banks and to a set within one cache bank of the plurality of cache banks.

Abstract: In one embodiment, a processor comprises a branch predictor to generate, in association with a program loop, a frozen history vector comprising a snapshot of a branch history vector; track a current iteration of the program loop; and provide a prediction for a branch instruction associated with the program loop, the prediction based on the frozen history vector and the current iteration of the program loop.