Abstract: Systems and methods are directed to prefetch mechanisms involving non-equal magnitude stride values. A non-equal magnitude functional relationship between successive stride values, may be detected, wherein the stride values are based on distances between target addresses of successive load instructions. At least a next stride value for prefetching data, may be determined, wherein the next stride value is based on the non-equal magnitude functional relationship and a previous stride value. Data prefetch may be from at least one prefetch address calculated based on the next stride value and a previous target address. The non-equal magnitude functional relationship may include a logarithmic relationship corresponding to a binary search algorithm.

Abstract: Systems and methods for managing access to a cache relate to determining one or more execute permissions associated with a write-address of a write-request to the cache. The cache may be a unified cache for storing data as well as instructions. If there is a write-miss in the cache for the write-request, a cache controller may determine whether to implement a write-allocate policy or a write-no-allocate policy for servicing the write-miss, based on the one or more execute permissions. The one or more execute permissions can relate to a privilege level associated with the write-address. Execute permissions of a producing agent which generated the write-request and an execute permission of a consuming agent which can execute from the write-address may be based on the privilege levels of the producing agent and the consuming agent, respectively.

Abstract: Aspects disclosed herein relate to combining instructions to load data from or store data in memory while processing instructions in processors. An exemplary method includes detecting a pattern of pipelined instructions to access memory using a first portion of available bus width and, in response to detecting the pattern, combining the pipelined instructions into a single instruction to access the memory using a second portion of the available bus width that is wider than the first portion. Devices including processors using disclosed aspects may execute currently available software in a more efficient manner without the software being modified.

Abstract: Systems and methods for identifying candidate load instructions for prefetch operations based on at least instruction encoding of the load instructions, include an identifier based on a function of at least one or more fields of a load instruction and optionally, a subset of bits of the PC value of the load instruction, wherein the one or more fields exclude a full address or program counter (PC) value of the load instruction. Prefetch mechanisms, including a prefetch table indexed by the identifier, can determine whether the load instruction is a candidate load instruction for prefetching load data, based on the identifier. The function may be a hash, a concatenation, or a combination thereof, of one or more bits of the one or more fields. The fields include one or more of a base register, a destination register, an immediate offset, an offset register, or other bits of instruction encoding of the load instruction.

Abstract: Predicting memory instruction punts in a computer processor using a punt avoidance table (PAT) are disclosed. In one aspect, an instruction processing circuit accesses a PAT containing entries each comprising an address of a memory instruction. Upon detecting a memory instruction in an instruction stream, the instruction processing circuit determines whether the PAT contains an entry having an address of the memory instruction. If so, the instruction processing circuit prevents the detected memory instruction from taking effect before at least one pending memory instruction older than the detected memory instruction, to preempt a memory instruction punt. In some aspects, the instruction processing circuit may determine, upon execution of a pending memory instruction, whether a hazard associated with the detected memory instruction has occurred. If so, an entry for the detected memory instruction is generated in the PAT.

Abstract: A memory structure compresses a portion of a memory tag using an indexed tag compression structure. A set of higher order bits of the memory tag may be stored in the indexed tag compression structure, where the set of higher order bits are identified by an index value. A tag array stores a set of lower order bits of the memory tag and the index value identifying the entry in the tag compression structure storing the set of higher order bits of the memory tag. The memory tag may comprise at least a portion of a memory address of a data element stored in a data array.

Abstract: Systems and methods for mitigating influence of wrong-path branch instructions in branch prediction include a branch prediction write queue. A first entry of the branch prediction write queue is associated with a first branch instruction based on an order in which the first branch instruction is fetched. Upon speculatively executing the first branch instruction, a correct direction of the first branch instruction is written in the first entry. Prior to committing the first branch instruction, the branch prediction write queue is configured to update one or more branch prediction mechanisms based on the first entry if the first branch instruction was speculatively executed in a correct-path. Updates to the one or more branch prediction mechanisms based on the first entry are prevented if the first branch instruction was speculatively executed in a wrong-path.

Abstract: A memory structure compresses a portion of a memory tag using an indexed tag compression structure. A set of higher order bits of the memory tag may be stored in the indexed tag compression structure, where the set of higher order bits are identified by an index value. A tag array stores a set of lower order bits of the memory tag and the index value identifying the entry in the tag compression structure storing the set of higher order bits of the memory tag. The memory tag may comprise at least a portion of a memory address of a data element stored in a data array.

Abstract: Indexing subroutine entries in a branch target instruction cache (BTIC) using a target address of the subroutine. The instructions returned by the BTIC may be injected into an execution pipeline to remove a cycle bubble in the processing pipeline.

Abstract: Fusing immediate value, write-based instructions in instruction processing circuits, and related processor systems, methods, and computer-readable media are disclosed. In one embodiment, a first instruction indicating an operation writing an immediate value to a register is detected by an instruction processing circuit. The circuit also detects at least one subsequent instruction indicating an operation that overwrites at least one first portion of the register while maintaining a value of a second portion of the register. The at least one subsequent instruction is converted (or replaced) with a fused instruction(s), which indicates an operation writing the at least one first portion and the second portion of the register.

Abstract: The disclosure relates to predicting simple and polymorphic branch instructions. An embodiment of the disclosure detects that a program instruction is a branch instruction, determines whether a program counter for the branch instruction is stored in a program counter filter, and, if the program counter is stored in the program counter filter, prevents the program counter from being stored in a first level predictor.

Abstract: Removing invalid literal load values, and related circuits, methods, and computer-readable media are disclosed. In one aspect, an instruction processing circuit provides a literal load table containing one or more entries comprising an address and a cached literal load value. Upon detecting a literal load instruction in an instruction stream, the instruction processing circuit determines whether the literal load table contains an entry having an address of the literal load instruction. If so, the instruction processing circuit removes the literal load instruction from the instruction stream, and provides the cached literal load value stored in the entry to at least one dependent instruction. The instruction processing circuit further determines whether an invalidity indicator for the literal load table has been received. If so, the instruction processing circuit flushes the literal load table. The invalidity indicator may be generated responsive to modification of a constant table.

Abstract: Establishing a branch target instruction cache (BTIC) entry for subroutine returns to reduce pipeline bubbles, and related systems, methods, and computer-readable media are disclosed. In one embodiment, a method of establishing a BTIC entry includes detecting a subroutine call in an execution pipeline. In response, at least one instruction fetched sequential to the subroutine call is written as a branch target instruction in a BTIC entry for a subroutine return. A next instruction fetch address is calculated, and is written into a next instruction fetch address field in the BTIC entry. In this manner, the BTIC may provide correct branch target instruction and next instruction fetch address data for the subroutine return, even if the subroutine return is encountered for the first time or the subroutine is called from different calling locations.

Abstract: Accelerating constant value generation using a computed constants table, and related circuits, methods, and computer-readable media are disclosed. In one aspect, an instruction processing circuit provides a computed constants table containing one or more entries each comprising an address and a constant value. The instruction processing circuit is configured to detect, in an instruction stream, a constant-generating instruction sequence, and to determine whether an address of the constant-generating instruction sequence is present in an entry of the computed constants table. If the address of the constant-generating instruction sequence is present in the entry of the computed constants table, the instruction processing circuit provides a constant value stored in the entry for execution of at least one dependent instruction on the constant-generating instruction sequence.

Abstract: Propagating constant values using a computed constants table, and related apparatuses and methods are disclosed. In one aspect, an apparatus comprises an instruction processing circuit configured to provide a computed constants table containing one or more entries. Each entry of the computed constants table comprises an attribute and a computed constant value. The instruction processing circuit is configured to detect a deterministic instruction in an instruction stream. Upon detecting the deterministic instruction, the instruction processing circuit determines whether an attribute of the deterministic instruction matches an entry of the computed constants table. If so, the instruction processing circuit provides the computed constant value stored in the entry to at least one dependent instruction. In this manner, a computed constant value may be propagated between instructions without requiring the deterministic instruction to be re-executed.

Abstract: Predicting literal load values using a literal load prediction table, and related circuits, methods, and computer-readable media are disclosed. In one aspect, an instruction processing circuit provides a literal load prediction table containing one or more entries, each comprising an address and a literal load value. Upon detecting a literal load instruction in an instruction stream, the instruction processing circuit determines whether the literal load prediction table contains an entry having an address of the literal load instruction. If so, the instruction processing circuit provides the predicted literal load value stored in the entry to at least one dependent instruction. The instruction processing circuit subsequently determines whether the predicted literal load value matches the actual literal load value loaded by the literal load instruction. If a mismatch exists, the instruction processing circuit initiates a misprediction recovery.

Abstract: Fusing conditional write instructions having opposite conditions in instruction processing circuits and related processor systems, methods, and computer-readable media are disclosed. In one embodiment, a first conditional write instruction writing a first value to a target register based on evaluating a first condition is detected by an instruction processing circuit. The circuit also detects a second conditional write instruction writing a second value to the target register based on evaluating a second condition that is a logical opposite of the first condition. Either the first condition or the second condition is selected as a fused instruction condition, and corresponding values are selected as if-true and if-false values. A fused instruction is generated for selectively writing the if-true value to the target register if the fused instruction condition evaluates to true, and selectively writing the if-false value to the target register if the fused instruction condition evaluates to false.

Abstract: Eliminating redundant masking operations in instruction processing circuits and related processor systems, methods, and computer-readable media are disclosed. In one embodiment, a first instruction in an instruction stream indicating an operation writing a value to a first register is detected by an instruction processing circuit, the value having a value size less than a size of the first register. The circuit also detects a second instruction in the instruction stream indicating a masking operation on the first register. The masking operation is eliminated upon a determination that the masking operation indicates a read operation and a write operation on the first register and has an identity mask size equal to or greater than the value size. In this manner, the elimination of the masking operation avoids potential read-after-write hazards and improves performance of a CPU by removing redundant operations from an execution pipeline.

Abstract: Systems and method for memory management units (MMUs) configured to automatically pre-fill a translation lookaside buffer (TLB) with address translation entries expected to be used in the future, thereby reducing TLB miss rate and improving performance. The TLB may be pre-filled with translation entries, wherein addresses corresponding to the pre-fill may be selected based on predictions. Predictions may be derived from external devices, or based on stride values, wherein the stride values may be a predetermined constant or dynamically altered based on access patterns. Pre-filling the TLB may effectively remove latency involved in determining address translations for TLB misses from the critical path.

Abstract: Techniques for adaptive thread scheduling on a plurality of cores for reducing system energy are described. In one embodiment, a thread scheduler receives leakage current information associated with the plurality of cores. The leakage current information is employed to schedule a thread on one of the plurality of cores to reduce system energy usage. On chip calibration of the sensors is also described.