Abstract: A method and a processor load/store unit (LSU) are described for performing store-to-load forwarding (STLF) from an interlocking store. STLF is performed when a starting address of the store and the load do not match, or when a data size of the store is smaller than a data size of the load. The LSU detects a load that interlocks with a store, and determines whether all or only a portion of data bytes needed by the load can be provided by the interlocking store. If it is determined that only a portion of the data bytes needed by the load can be provided by the interlocking store, then that portion of the data bytes is provided by a store data buffer (SDB) and the remaining portion of the data bytes needed by the load is provided by a data cache (DC). Otherwise, the SDB provides all of the data bytes.

Abstract: A method and microprocessor are described for efficiently executing load instructions out-of-order (speculatively). The microprocessor includes an enhanced load store unit (LSU) and an enhanced instruction decoder. The enhanced LSU receives a plurality of out-of-order value addresses, and sends a resync signal to the enhanced instruction decoder when an execution error associated with a particular load instruction occurs. The enhanced instruction decoder stores a specific address associated with the particular load instruction, and increments a counter value that indicates how many times the resync signal was sent by the resync predictor. When the counter value reaches a predetermined threshold, subsequent load instructions from the specific address are executed in order (non-speculatively).

Abstract: A method and a processor load/store unit (LSU) are described for performing store-to-load forwarding (STLF) from an interlocking store. STLF is performed when a starting address of the store and the load do not match, or when a data size of the store is smaller than a data size of the load. The LSU detects a load that interlocks with a store, and determines whether all or only a portion of data bytes needed by the load can be provided by the interlocking store. If it is determined that only a portion of the data bytes needed by the load can be provided by the interlocking store, then that portion of the data bytes is provided by a store data buffer (SDB) and the remaining portion of the data bytes needed by the load is provided by a data cache (DC). Otherwise, the SDB provides all of the data bytes.

Abstract: A method and microprocessor are described for efficiently executing load instructions out-of-order (speculatively). The microprocessor includes an enhanced load store unit (LSU) and an enhanced instruction decoder. The enhanced LSU receives a plurality of out-of-order value addresses, and sends a resync signal to the enhanced instruction decoder when an execution error associated with a particular load instruction occurs. The enhanced instruction decoder stores a specific address associated with the particular load instruction, and increments a counter value that indicates how many times the resync signal was sent by the resync predictor. When the counter value reaches a predetermined threshold, subsequent load instructions from the specific address are executed in order (non-speculatively).

Abstract: A system and method for data forwarding from a store instruction to a load instruction during out-of-order execution, when the load instruction address matches against multiple older uncommitted store addresses or if the forwarding fails during the first pass due to any other reason. In a first pass, the youngest store instruction in program order of all store instructions older than a load instruction is found and an indication to the store buffer entry holding information of the youngest store instruction is recorded. In a second pass, the recorded indication is used to index the store buffer and the store bypass data is forwarded to the load instruction. Simultaneously, it is verified if no new store, younger than the previously identified store and older than the load has not been issued due to out-of-order execution.

Abstract: A system and method for data forwarding from a store instruction to a load instruction during out-of-order execution, when the load instruction address matches against multiple older uncommitted store addresses or if the forwarding fails during the first pass due to any other reason. In a first pass, the youngest store instruction in program order of all store instructions older than a load instruction is found and an indication to the store buffer entry holding information of the youngest store instruction is recorded. In a second pass, the recorded indication is used to index the store buffer and the store bypass data is forwarded to the load instruction. Simultaneously, it is verified if no new store, younger than the previously identified store and older than the load has not been issued due to out-of-order execution.

Abstract: A system and method for linking speculative results of load operations to register values. A system includes a memory file including an entry configured to store a first addressing pattern and a first tag. The memory file is configured to compare the first addressing pattern to a second addressing pattern of a load operation, and to link a data value identified by the first tag to a speculative result of the load operation if there is a match. The system further includes an execution core coupled to the memory file and configured to access the speculative result when executing a second operation that is dependent on the load operation, and a load store unit coupled to the memory file and configured to verify the link between the data value and the speculative result of the load operation by performing a comparison between one or more addresses.

Abstract: A multimedia execution unit configured to perform vectored floating point and integer instructions. The execution unit may include an add/subtract pipeline having far and close data paths. The far path is configured to handle effective addition operations and effective subtraction operations for operands having an absolute exponent difference greater than one. The close path is configured to handle effective subtraction operations for operands having an absolute exponent difference less than or equal to one. The close path is configured to generate two output values, wherein one output value is the first input operand plus an inverted version of the second input operand, while the second output value is equal to the first output value plus one. Selection of the first or second output value in the close path effectuates the round-to-nearest operation for the output of the adder.

Abstract: A multimedia execution unit configured to perform vectored floating point and integer instructions. The execution unit may include an add/subtract pipeline having far and close data paths. The far path is configured to handle effective addition operations and effective subtraction operations for operands having an absolute exponent difference greater than one. The close path is configured to handle effective subtraction operations for operands having an absolute exponent difference less than or equal to one. The close path is configured to generate two output values, wherein one output value is the first input operand plus an inverted version of the second input operand, while the second output value is equal to the first output value plus one. Selection of the first or second output value in the close path effectuates the round-to-nearest operation for the output of the adder.

Abstract: A multimedia execution unit configured to perform vectored floating point and integer instructions. The execution unit may include an add/subtract pipeline having far and close data paths. The far path is configured to handle effective addition operations and effective subtraction operations for operands having an absolute exponent difference greater than one. The close path is configured to handle effective subtraction operations for operands having an absolute exponent difference less than or equal to one. The close path is configured to generate two output values, wherein one output value is the first input operand plus an inverted version of the second input operand, while the second output value is equal to the first output value plus one. Selection of the first or second output value in the close path effectuates the round-to-nearest operation for the output of the adder.