Abstract: Method and system for managing a speculative transaction in a processing unit is provided. The speculative transaction is initiated by dispatching a first instruction indicating start of the speculative transaction. One or more register file (RF) entries are marked as pre-transaction memory (PTM), in response to the initiating. At least one second instruction targeting at least one of the marked RF entries is dispatched, while the transaction is active, wherein the at least one second instruction writes new result data into the at least one RF entry. Previous result data evicted from the at least one RF entry by the new result data, is saved into a history buffer (HB) entry. The HB entry is marked as PTM, in response to the saving, wherein the processing unit, upon detecting a trigger, is rolled back to a state before the initiating the transaction by restoring the previous result data to the at least one RF entry.

Abstract: Mechanisms are provided, in a processor, for executing instructions that are younger than a previously dispatched synchronization (sync) instruction is provided. An instruction sequencer unit of the processor dispatches a sync instruction. The sync instruction is sent to a nest of one or more devices outside of the processor. The instruction sequencer unit dispatches a subsequent instruction after dispatching the sync instruction. The dispatching of the subsequent instruction after dispatching the sync instruction is performed prior to receiving a sync acknowledgement response from the nest. The instruction sequencer unit performs a completion of the subsequent instruction based on whether completion of the subsequent instruction is dependent upon receiving the sync acknowledgement from the nest and completion of the sync instruction.

Abstract: A system and process for managing thread transitions includes providing two data register sets coupled to a processor and using, by the processor, the two register sets as first-level registers for thread execution. A determination is made whether a quantity of the first-level registers needed to execute one or more threads exceeds a quantity of the first-level registers of the two data register sets. Responsive to determining that the quantity of the first-level registers needed to execute the one or more threads exceeds the quantity of the first-level registers of the two data register sets, a portion of main memory or cache memory is assigned as second-level registers where the second-level registers serve as registers of at least one of the two data register sets for executing the one or more threads.

Abstract: Executing system call vectored (SCV) instructions in a multi-slice processor including receiving, by an instruction fetch unit, a SCV instruction, wherein the SCV instruction is a system call from an operating system; sending the SCV instruction to a branch issue queue; determining, by the branch issue queue, that the SCV instruction is next-to-complete; issuing the SCV instruction to a branch resolution unit; and executing the SCV instruction by the branch resolution unit.

Abstract: Method and system for writing a history buffer in a processing unit is provided. At least a first instruction and a second instruction are dispatched in a single processing cycle, targeting a same register file entry. The processing unit includes two or more processing slices, each processing slice comprising a corresponding history buffer and at least a portion of a register file. Upon determining that first result data corresponding to the first instruction is older than second result data corresponding to the second instruction, the first result data is written into a history buffer bypassing the register file entry, in response to the determination. Further, the second result data is written into the register file entry.

Abstract: Mechanisms are provided, in a processor, for executing instructions that are younger than a previously dispatched synchronization (sync) instruction is provided. An instruction sequencer unit of the processor dispatches a sync instruction. The sync instruction is sent to a nest of one or more devices outside of the processor. The instruction sequencer unit dispatches a subsequent instruction after dispatching the sync instruction. The dispatching of the subsequent instruction after dispatching the sync instruction is performed prior to receiving a sync acknowledgement response from the nest. The instruction sequencer unit performs a completion of the subsequent instruction based on whether completion of the subsequent instruction is dependent upon receiving the sync acknowledgement from the nest and completion of the sync instruction.

Abstract: A system and process for managing thread transitions includes determining that a transition is to be made regarding the relative use of two data register sets where the two data register sets are used by a processor as first-level registers for thread execution. Based on the transition determination, a determination is made whether to move thread data in at least one of the first-level registers to second-level registers. Responsive to determining to move the thread data, a portion of main memory or cache memory is assigned as the second-level registers where the second-level registers serve as registers of at least one of the two data register sets for executing a thread. The thread data from the at least one first-level register is moved to the second-level registers based on the move determination.

Abstract: Executing system call vectored (SCV) instructions in a multi-slice processor including receiving, by an instruction fetch unit, a SCV instruction, wherein the SCV instruction is a system call from an operating system; sending the SCV instruction to a branch issue queue; determining, by the branch issue queue, that the SCV instruction is next-to-complete; issuing the SCV instruction to a branch resolution unit; and executing the SCV instruction by the branch resolution unit.

Abstract: A multi-slice processor that includes execution slices, and a history buffer, where the history buffer includes a plurality of entries, where at least one of the entries includes transactional memory state data that corresponds to a transactional memory instruction updating a transaction memory state, and where operation of such a multi-slice processor includes: propagating a flush signal to the plurality of entries of the history buffer; responsive to the flush signal, generating, from an entry of the history buffer, the transactional memory state data; and restoring to a transactional memory state in dependence upon the transactional memory state data.

Abstract: Executing system call vectored (SCV) instructions in a multi-slice processor including receiving, by an instruction fetch unit, a SCV instruction, wherein the SCV instruction is a system call from an operating system; sending the SCV instruction to a branch issue queue; determining, by the branch issue queue, that the SCV instruction is next-to-complete; issuing the SCV instruction to a branch resolution unit; and executing the SCV instruction by the branch resolution unit.

Abstract: A system and process for managing thread transitions includes determining that a transition is to be made regarding the relative use of two data register sets where the two data register sets are used by a processor as first-level registers for thread execution. Based on the transition determination, a determination is made whether to move thread data in at least one of the first-level registers to second-level registers. Responsive to determining to move the thread data, a portion of main memory or cache memory is assigned as the second-level registers where the second-level registers serve as registers of at least one of the two data register sets for executing a thread. The thread data from the at least one first-level register is moved to the second-level registers based on the move determination.

Abstract: A hardware execution unit within a processor core executes a second instruction, which is part of a software thread, and which is executed out of order within the software thread. A sticky bit flip detection hardware device detects a change to a sticky bit in a floating-point status and control register (FPSCR) within the processor core. An instruction issue hardware unit identifies a first instruction that is in the software thread that is capable of reading or clearing the sticky bit. A flushing execution unit flushes all results of instructions from an instruction completion table (ICT) that include and are after the first instruction in the software thread. A hardware dispatch device dispatches all instructions that include and are after the first instruction in the software thread for execution by one or more hardware execution units within the processor core in a next-to-complete (NTC) sequential order.

Abstract: A multi-slice processor that includes execution slices, and a history buffer, where the history buffer includes a plurality of entries, where at least one of the entries includes transactional memory state data that corresponds to a transactional memory instruction updating a transaction memory state, and where operation of such a multi-slice processor includes: propagating a flush signal to the plurality of entries of the history buffer; responsive to the flush signal, generating, from an entry of the history buffer, the transactional memory state data; and restoring to a transactional memory state in dependence upon the transactional memory state data.

Abstract: Various systems, processes, products, and techniques may be used to manage thread transitions. In particular implementations, a system and process for managing thread transitions may include the ability to determine that a transition is to be made regarding the relative use of two data register sets and determine, based on the transition determination, whether to move thread data in at least one of the data register sets to second-level registers. The system and process may also include the ability to move the thread data from at least one data register set to second-level registers based on the move determination.

Abstract: Method and system for restoring data to a register file of a processing unit are provided. A history buffer entry (HBE) is marked for restoration to a register file entry. Result data and control information is sent from the HBE to an Issue Queue (ISQ). The ISQ issues an instruction for loading the result data into the register file entry based on the control information. A write back operation is performed to restore the result data to the register file entry, in response to issuing of the instruction.

Abstract: Method and system for restoring results to a register file of a processing unit is provided. An instruction is dispatched in a processing slice of the processing unit, targeting a register file, wherein the processing unit includes two or more processing slices, each processing slice including a corresponding history buffer and at least a portion of a register file. The processing unit evicts previous result data from the register file entry to a history buffer corresponding to the processing slice, by writing new result data into the register file entry, in response to the instruction. The processing unit detects a trigger condition relating to a rollback of the processing unit to a previous state, and restores the previous result data from the history buffer to the register file entry, in response to the trigger.

Abstract: Method and system for writing a history buffer in a processing unit is provided. At least a first instruction and a second instruction are dispatched in a single processing cycle, targeting a same register file entry. The processing unit includes two or more processing slices, each processing slice comprising a corresponding history buffer and at least a portion of a register file. Upon determining that first result data corresponding to the first instruction is older than second result data corresponding to the second instruction, the first result data is written into a history buffer bypassing the register file entry, in response to the determination. Further, the second result data is written into the register file entry.

Abstract: Method and system for managing a speculative transaction in a processing unit is provided. The speculative transaction is initiated by dispatching a first instruction indicating start of the speculative transaction. One or more register file (RF) entries are marked as pre-transaction memory (PTM), in response to the initiating. At least one second instruction targeting at least one of the marked RF entries is dispatched, while the transaction is active, wherein the at least one second instruction writes new result data into the at least one RF entry. Previous result data evicted from the at least one RF entry by the new result data, is saved into a history buffer (HB) entry. The HB entry is marked as PTM, in response to the saving, wherein the processing unit, upon detecting a trigger, is rolled back to a state before the initiating the transaction by restoring the previous result data to the at least one RF entry.

Abstract: Within a processor, speculative finishes of load instructions only are tracked in a speculative finish table by maintaining an oldest load instruction of a thread in the speculative finish table after data is loaded for the oldest load instruction, wherein a particular queue index tag assigned to the oldest load instruction by an execution unit points to a particular entry in the speculative finish table, wherein the oldest load instruction is waiting to be finished dependent upon an error check code result. Responsive to a flow unit receiving the particular queue index tag with an indicator that the error check code result for data retrieved for the oldest load instruction is good, finishing the oldest load instruction in the particular entry pointed to by the queue index tag and writing an instruction tag stored in the entry for the oldest load instruction out of the speculative finish table for completion.

Abstract: Within a processor, speculative finishes of load instructions only are tracked in a speculative finish table by maintaining an oldest load instruction of a thread in the speculative finish table after data is loaded for the oldest load instruction, wherein a particular queue index tag assigned to the oldest load instruction by an execution unit points to a particular entry in the speculative finish table, wherein the oldest load instruction is waiting to be finished dependent upon an error check code result. Responsive to a flow unit receiving the particular queue index tag with an indicator that the error check code result for data retrieved for the oldest load instruction is good, finishing the oldest load instruction in the particular entry pointed to by the queue index tag and writing an instruction tag stored in the entry for the oldest load instruction out of the speculative finish table for completion.