Patent application number | Description | Published |
20080229069 | System, Method And Software To Preload Instructions From An Instruction Set Other Than One Currently Executing - An instruction preload instruction executed in a first processor instruction set operating mode is operative to correctly preload instructions in a different, second instruction set. The instructions are pre-decoded according to the second instruction set encoding in response to an instruction set preload indicator (ISPI). In various embodiments, the ISPI may be set prior to executing the preload instruction, or may comprise part of the preload instruction or the preload target address. | 09-18-2008 |
20080250229 | System, Method and Software to Preload Instructions from a Variable-Length Instruction Set with Proper Pre-Decoding - In a processor executing instructions from a variable-length instruction set, a preload instruction is operative to retrieve from memory a data block corresponding to an instruction cache line, pre-decode instructions from a variable-length instruction set in the data block, and load the instructions and pre-decode information into the instruction cache. An instruction execution unit indicates to a pre-decoder the position within the data block of a first valid instruction. The pre-decoder successively determines the length of each instruction and hence the instruction boundaries. An instruction cache line offset indicator that identifies the position of the first valid instruction may be generated and provided to the pre-decoder in a variety of ways. | 10-09-2008 |
20080288753 | Methods and Apparatus for Emulating the Branch Prediction Behavior of an Explicit Subroutine Call - An apparatus for emulating the branch prediction behavior of an explicit subroutine call is disclosed. The apparatus includes a first input which is configured to receive an instruction address and a second input. The second input is configured to receive predecode information which describes the instruction address as being related to an implicit subroutine call to a subroutine. In response to the predecode information, the apparatus also includes an adder configured to add a constant to the instruction address defining a return address, causing the return address to be stored to an explicit subroutine resource, thus, facilitating subsequent branch prediction of a return call instruction. | 11-20-2008 |
20090094444 | Link Stack Repair of Erroneous Speculative Update - Whenever a link address is written to the link stack, the prior value of the link stack entry is saved, and is restored to the link stack after a link stack push operation is speculatively executed following a mispredicted branch. This condition is detected by maintaining a count of the total number of uncommitted link stack write instructions in the pipeline, and a count of the number of uncommitted link stack write instructions ahead of each branch instruction. When a branch is evaluated and determined to have been mispredicted, the count associated with it is compared to the total count. A discrepancy indicates a link stack write instruction was speculatively issued into the pipeline after the mispredicted branch instruction, and pushed a link address onto the link stack. The prior link address is restored to the link stack from the link stack restore buffer. | 04-09-2009 |
20090119485 | Predecode Repair Cache For Instructions That Cross An Instruction Cache Line - A predecode repair cache is described in a processor capable of fetching and executing variable length instructions having instructions of at least two lengths which may be mixed in a program. An instruction cache is operable to store in an instruction cache line instructions having at least a first length and a second length, the second length longer than the first length. A predecoder is operable to predecode instructions fetched from the instruction cache that have invalid predecode information to form repaired predecode information. A predecode repair cache is operable to store the repaired predecode information associated with instructions of the second length that span across two cache lines in the instruction cache. Methods for filling the predecode repair cache and for executing an instruction that spans across two cache lines are also described. | 05-07-2009 |
20100023696 | Methods and System for Resolving Simultaneous Predicted Branch Instructions - A method of resolving simultaneous branch predictions prior to validation of the predicted branch instruction is disclosed. The method includes processing two or more predicted branch instructions, with each predicted branch instruction having a predicted state and a corrected state. The method further includes selecting one of the corrected states. Should one of the predicted branch instructions be mispredicted, the selected corrected state is used to direct future instruction fetches. | 01-28-2010 |
20100036987 | Apparatus and Methods for Speculative Interrupt Vector Prefetching - Techniques for interrupt processing are described. An exceptional condition is detected in one or more stages of an instruction pipeline in a processor. In response to the detected exceptional condition and prior to the processor accepting an interrupt in response to the detected exceptional condition, an instruction cache is checked for the presence of an instruction at a starting address of an interrupt handler. The instruction at the starting address of the interrupt vector table is prefetched from storage above the instruction cache when the instruction is not present in the instruction cache to load the instruction in the instruction cache, whereby the instruction is made available in the instruction cache by the time the processor accepts the interrupt in response to the detected exceptional condition. | 02-11-2010 |
20100058032 | Effective Use of a BHT in Processor Having Variable Length Instruction Set Execution Modes - In a processor executing instructions in at least a first instruction set execution mode having a first minimum instruction length and a second instruction set execution mode having a smaller, second minimum instruction length, line and counter index addresses are formed that access every counter in a branch history table (BHT), and reduce the number of index address bits that are multiplexed based on the current instruction set execution mode. In one embodiment, counters within a BHT line are arranged and indexed in such a manner that half of the BHT can be powered down for each access in one instruction set execution mode. | 03-04-2010 |
20100169615 | Preloading Instructions from an Instruction Set Other than a Currently Executing Instruction Set - A preload instruction in a first instruction set is executed at a processor. The preload instruction causes the processor to preload one or more instructions into an instruction cache. The pre-loaded instructions are pre-decoded according to a second instruction set that is different from the first instruction set. The preloaded instructions are pre-decoded according to the second instruction set in response to an instruction set preload indicator (ISPI). | 07-01-2010 |
20110219220 | Link Stack Repair of Erroneous Speculative Update - Whenever a link address is written to the link stack, the prior value of the link stack entry is saved, and is restored to the link stack after a link stack push operation is speculatively executed following a mispredicted branch. This condition is detected by maintaining a count of the total number of uncommitted link stack write instructions in the pipeline, and a count of the number of uncommitted link stack write instructions ahead of each branch instruction. When a branch is evaluated and determined to have been mispredicted, the count associated with it is compared to the total count. A discrepancy indicates a link stack write instruction was speculatively issued into the pipeline after the mispredicted branch instruction, and pushed a link address onto the link stack. The prior link address is restored to the link stack from the link stack restore buffer. | 09-08-2011 |
20110320790 | Link Stack Repair of Erroneous Speculative Update - Whenever a link address is written to the link stack, the prior value of the link stack entry is saved, and is restored to the link stack after a link stack push operation is speculatively executed following a mispredicted branch. This condition is detected by maintaining an incrementing tag register which is incremented by each link stack write instruction entering the pipeline, and a snapshot of the incrementing tag register, associated with each branch instruction. When a branch is evaluated and determined to have been mispredicted, the snapshot associated with it is compared to the incrementing tag register. A discrepancy indicates a link stack write instruction was speculatively issued into the pipeline after the mispredicted branch instruction, and pushed a link address onto the link stack, thus corrupting the link stack. The prior link address is restored to the link stack from the link stack restore buffer. | 12-29-2011 |
20130290683 | Eliminating Redundant Masking Operations Instruction Processing Circuits, And Related Processor Systems, Methods, And Computer-Readable Media - 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. | 10-31-2013 |
20130304993 | Method and Apparatus for Tracking Extra Data Permissions in an Instruction Cache - Systems and methods are disclosed for maintaining an instruction cache including extended cache lines and page attributes for main cache line portions of the extended cache lines and, at least for one or more predefined potential page-crossing instruction locations, additional page attributes for extra data portions of the corresponding extended cache lines. In addition, systems and methods are disclosed for processing page-crossing instructions fetched from an instruction cache having extended cache lines. | 11-14-2013 |
20130311754 | FUSING CONDITIONAL WRITE INSTRUCTIONS HAVING OPPOSITE CONDITIONS IN INSTRUCTION PROCESSING CIRCUITS, AND RELATED PROCESSOR SYSTEMS, METHODS, AND COMPUTER-READABLE MEDIA - 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. | 11-21-2013 |
20130311760 | Multi Level Indirect Predictor using Confidence Counter and Program Counter Address Filter Scheme - 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. | 11-21-2013 |
20130326195 | PREVENTING EXECUTION OF PARITY-ERROR-INDUCED UNPREDICTABLE INSTRUCTIONS, AND RELATED PROCESSOR SYSTEMS, METHODS, AND COMPUTER-READABLE MEDIA - Preventing execution of parity-error-induced unpredictable instructions, and related processor systems, methods, and computer-readable media are disclosed. In this regard, a method for processing instructions in a central processing unit (CPU) is provided. The method comprises decoding an instruction comprising a plurality of bits, and generating a parity error indicator indicating whether a parity error exists in the plurality of bits prior to execution of the instruction. If the parity error indicator indicates that the parity error exists in the plurality of bits, one or more of the plurality of bits are modified to indicate a no execution operation (NOP), without effecting a roll back of a program counter of the CPU and without re-decoding the instruction. In this manner, the possibility of the parity error causing an inadvertent execution of an unpredictable instruction is reduced. | 12-05-2013 |
20140006752 | Qualifying Software Branch-Target Hints with Hardware-Based Predictions | 01-02-2014 |
20140047221 | FUSING FLAG-PRODUCING AND FLAG-CONSUMING INSTRUCTIONS IN INSTRUCTION PROCESSING CIRCUITS, AND RELATED PROCESSOR SYSTEMS, METHODS, AND COMPUTER-READABLE MEDIA - Fusing flag-producing and flag-consuming instructions in instruction processing circuits and related processor systems, methods, and computer-readable media are disclosed. In one embodiment, a flag-producing instruction indicating a first operation generating a first flag result is detected in an instruction stream by an instruction processing circuit. The instruction processing circuit also detects a flag-consuming instruction in the instruction stream indicating a second operation consuming the first flag result as an input. The instruction processing circuit generates a fused instruction indicating the first operation generating the first flag result and indicating the second operation consuming the first flag result as the input. In this manner, as a non-limiting example, the fused instruction eliminates a potential for a read-after-write hazard between the flag-producing instruction and the flag-consuming instruction. | 02-13-2014 |
20140089598 | METHODS AND APPARATUS FOR MANAGING PAGE CROSSING INSTRUCTIONS WITH DIFFERENT CACHEABILITY - An instruction in an instruction cache line having a first portion that is cacheable, a second portion that is from a page that is non-cacheable, and crosses a cache line is prevented from executing from the instruction cache. An attribute associated with the non-cacheable second portion is tracked separately from the attributes of the rest of the instructions in the cache line. If the page crossing instruction is reached for execution, the page crossing instruction and instructions following are flushed and a non-cacheable request is made to memory for at least the second portion. Once the second portion is received, the whole page crossing instruction is reconstructed from the first portion saved in the previous fetch group. The page crossing instruction or portion thereof is returned with the proper attribute for a non-cached fetched instruction and the reconstructed instruction can be executed without being cached. | 03-27-2014 |
20140149722 | Fusing Immediate Value, Write-Based Instructions in Instruction Processing Circuits, and Related Processor Systems, Methods, and Computer-Readable Media - 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. In this manner, conversion of multiple instructions for generating a constant into the fused instruction(s) removes the potential for a read-after-write hazard and associated consequences caused by dependencies between certain instructions, while reducing a number of clock cycles required to process the instructions. | 05-29-2014 |
20140149726 | ESTABLISHING A BRANCH TARGET INSTRUCTION CACHE (BTIC) ENTRY FOR SUBROUTINE RETURNS TO REDUCE EXECUTION PIPELINE BUBBLES, AND RELATED SYSTEMS, METHODS, AND COMPUTER-READABLE MEDIA - 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. | 05-29-2014 |
20140281391 | METHOD AND APPARATUS FOR FORWARDING LITERAL GENERATED DATA TO DEPENDENT INSTRUCTIONS MORE EFFICIENTLY USING A CONSTANT CACHE - A processor to a store constant value (immediate or literal) in a cache upon decoding a move immediate instruction in which the immediate is to be moved (copied or written) to an architected register. The constant value is stored in an entry in the cache. Each entry in the cache includes a field to indicate whether its stored constant value is valid, and a field to associate the entry with an architected register. Once a constant value is stored in the cache, it is immediately available for forwarding to a processor pipeline where a decoded instruction may need the constant value as an operand. | 09-18-2014 |
20140281394 | METHOD TO IMPROVE SPEED OF EXECUTING RETURN BRANCH INSTRUCTIONS IN A PROCESSOR - An apparatus and method for executing call branch and return branch instructions in a processor by utilizing a link register stack. The processor includes a branch counter that is initialized to zero, and is set to zero each time the processor decodes a link register manipulating instruction other than a call branch instruction. The branch counter is incremented by one each time a call branch instruction is decoded and an address is pushed onto the link register stack. In response to decoding a return branch instruction and provided the branch counter is not zero, a target address for the decoded return branch instruction is popped off the link register stack, the branch counter is decremented, and there is no need to check the target address for correctness. | 09-18-2014 |
20140281405 | OPTIMIZING PERFORMANCE FOR CONTEXT-DEPENDENT INSTRUCTIONS - A processor includes a queue for storing instructions processed within the context of a current value of a register field, where for some embodiments the instruction is undefined or defined, depending upon the register field at time of processing. After a write instruction (an instruction that writes to the register field) executes, the queue is searched for any entries that contain instructions that depend upon the executed write instruction. Each such entry stores the value of the register field at the time the instruction in the entry was processed. If such an entry is found in the queue and its stored value of the register field does not match the value that the write instruction wrote to the register field, then the processor flushes the pipeline and restarts at a state so as to correctly execute the instruction. | 09-18-2014 |
20140281429 | ELIMINATING REDUNDANT SYNCHRONIZATION BARRIERS IN INSTRUCTION PROCESSING CIRCUITS, AND RELATED PROCESSOR SYSTEMS, METHODS, AND COMPUTER-READABLE MEDIA - Embodiments disclosed herein include eliminating redundant synchronization barriers from execution pipelines in instruction processing circuits. Related processor systems, methods, and computer-readable media are also disclosed. By tracking the occurrence of synchronization events, unnecessary software synchronization operations may be identified and eliminated, thus improving performance of a central processing unit (CPU). In one embodiment, a method for eliminating redundant synchronization barriers in an instruction stream is provided. The method comprises determining whether a next instruction comprises a synchronization barrier of a type corresponding to a first synchronization event. The method also comprises eliminating the next instruction from the instruction stream, responsive to determining that the next instruction comprises a synchronization barrier of a type corresponding to the first synchronization event. In this manner, the average number of instructions executed during each CPU clock cycle may be increased by avoiding unnecessary synchronization operations. | 09-18-2014 |