Abstract: A single unified level one instruction cache in which some lines may contain traces and other lines in the same congruence class may contain blocks of instructions consistent with conventional cache lines. Control is exercised over which lines are contained within the cache. This invention avoids inefficiencies in the cache by removing trace lines experiencing early exits from the cache, or trace lines that are short, by maintaining a few bits of information about the accuracy of the control flow in a trace cache line and using that information in addition to the LRU (Least Recently Used) bits that maintain the recency information of a cache line, in order to make a replacement decision.

Abstract: A design structure embodied in a machine readable storage medium for designing, manufacturing, and/or testing a design for a single unified level one instruction(s) cache in which some lines may contain traces and other lines in the same congruence class may contain blocks of instruction(s) consistent with conventional cache lines is provided. Formation of trace lines in the cache is delayed on initial operation of the system to assure quality of the trace lines stored.

Abstract: A design structure embodied in a machine readable storage medium for at least one of designing, manufacturing, and testing a design for a single unified level one instruction cache in which some lines may contain traces and other lines in the same congruence class may contain blocks of instructions consistent with conventional cache lines is provided. Instruction branches are predicted taken or not taken using a highly accurate branch history table (BHT). Branches that are predicted not taken are appended to a trace buffer and the next basic block is constructed from the remaining instructions in the fetch buffer. Branches that are predicted taken flush the remaining fetch buffer and the next address is determined using a Branch Target Address Register (BTAC).

Abstract: A design structure embodied in a machine readable storage medium for at least one of designing, manufacturing, and testing a design for register renaming allows processor hardware to use a larger set of registers than the architected registers visible to the compiler. This larger set of registers is called the physical register file. Thus, dynamically renaming every compiler-suggested architected register to a microarchitecture-specific physical register, allows the processor to overcome name dependencies and the hazards (pipeline slowdowns) induced by name dependencies.

Abstract: A method and apparatus for executing instructions in a pipeline processor. The method decreases the latency between an instruction cache and a pipeline processor when bubbles occur in the processing stream due to an execution of a branch correction, or when an interrupt changes the sequence of an instruction stream. The latency is reduced when a decode stage for detecting branch prediction and a related instruction queue location have invalid data representing a bubble in the processing stream. Instructions for execution are inserted in parallel into the decode stage and instruction queue, thereby reducing by one cycle time the length of the pipeline stage.

Abstract: A processor includes an execution unit and instruction sequencing logic that fetches instructions for execution. The instruction sequencing logic includes a branch target address cache having a branch target buffer containing a plurality of entries each associating at least a portion of a branch instruction address with a predicted branch target address. The branch target address cache accesses the branch target buffer using a branch instruction address to obtain a predicted branch target address for use as an instruction fetch address. The branch target address cache also includes a filter buffer that buffers one or more candidate branch target address predictions. The filter buffer associates a respective confidence indication indicative of predictive accuracy with each candidate branch target address prediction. The branch target address cache promotes candidate branch target address predictions from the filter buffer to the branch target buffer based upon their respective confidence indications.

Abstract: A single unified level one instruction cache in which some lines may contain traces and other lines in the same congruence class may contain blocks of instructions consistent with conventional cache lines. Instruction branches are predicted taken or not taken using a highly accurate branch history table (BHT). Branches that are predicted not taken are appended to a trace buffer and the next basic block is constructed from the remaining instructions in the fetch buffer. Branches that are predicted taken flush the remaining fetch buffer and the next address is determined using a Branch Target Address Register (BTAC).

Abstract: A single unified level one instruction cache in which some lines may contain traces and other lines in the same congruence class may contain blocks of instructions consistent with conventional cache lines. Control is exercised over which lines are contained within the cache. This invention avoids inefficiencies in the cache by removing trace lines experiencing early exits from the cache, or trace lines that are short, by maintaining a few bits of information about the accuracy of the control flow in a trace cache line and using that information in addition to the LRU (Least Recently Used) bits that maintain the recency information of a cache line, in order to make a replacement decision.

Abstract: A single unified level one instruction cache in which some lines may contain traces and other lines in the same congruence class may contain blocks of instructions consistent with conventional cache lines. Power is conserved by guiding access to lines stored in the cache and lowering cache clock speed relative to the central processor clock speed.

Abstract: A single unified level one instruction(s) cache in which some lines may contain traces and other lines in the same congruence class may contain blocks of instruction(s) consistent with conventional cache lines. Formation of trace lines in the cache is delayed on initial operation of the system to assure quality of the trace lines stored.

Abstract: A single unified level one instruction cache in which some lines may contain traces and other lines in the same congruence class may contain blocks of instructions consistent with conventional cache lines. A mechanism is described for indexing into the cache, and selecting the desired line. Control is exercised over which lines are contained within the cache. Provision is made for selection between a trace line and a conventional line when both match during a tag compare step.

Abstract: Register renaming as contemplated by this invention allows processor hardware to use a larger set of registers than the architected registers visible to the compiler. This larger set of registers is called the physical register file. Thus, dynamically renaming every compiler-suggested architected register to a microarchitecture-specific physical register, allows the processor to overcome name dependencies and the hazards (pipeline slowdowns) induced by name dependencies. The invention here described differs from prior renaming techniques in that it extracts significant benefit from renaming with a fraction of the number of physical registers previously used for this process. The invention therefore also simplifies the logic involved in supporting the use of the physical registers.

Abstract: An LRU array and method for tracking the accessing of lines of an associative cache. The most recently accessed lines of the cache are identified in the table, and cache lines can be blocked from being replaced. The LRU array contains a data array having a row of data representing each line of the associative cache, having a common address portion. A first set of data for the cache line identifies the relative age of the cache line for each way with respect to every other way. A second set of data identifies whether a line of one of the ways is not to be replaced. For cache line replacement, the cache controller will select the least recently accessed line using contents of the LRU array, considering the value of the first set of data, as well as the value of the second set of data indicating whether or not a way is locked. Updates to the LRU occur after each pre-fetch or fetch of a line or when it replaces another line in the cache memory.

Abstract: A method and apparatus for executing instructions in a pipeline processor. The method decreases the latency between an instruction cache and a pipeline processor when bubbles occur in the processing stream due to an execution of a branch correction, or when an interrupt changes the sequence of an instruction stream. The latency is reduced when a decode stage for detecting branch prediction and a related instruction queue location have invalid data representing a bubble in the processing stream. Instructions for execution are inserted in parallel into the decode stage and instruction queue, thereby reducing by one cycle time the length of the pipeline stage.

Abstract: A method, apparatus, and article of manufacture for performing thread switch tuning for optimal performance of a program executed by a computer data processing system having a multithreaded processor.