Abstract: An apparatus and a method of data processing system that uses multiply-accumulate instructions. The apparatus for processing data includes, a special register bank of N-bit data processing registers, a general register bank of N-bit data processing registers, a selector, a multiplier and an accumulator. The selector is coupled to the special register bank and the general register bank and is used for selecting one of the special and general register banks and outputting N-bit data from the selected register banks. The outputted N-bit data and the N-bit data held in the general register bank form a 2N-bit addition operand. The multiplier is used for performing multiply operation upon a first operand and a second operand and outputting an 2N-bit result. The accumulator is coupled to the multiplier, the selector and the general register bank and is used for performing accumulate operation upon the 2N-bit result and the 2N-bit addition operand and outputting a 2N-bit accumulated result.

Abstract: According to one embodiment, a method features operations for executing instructions in an instruction window. The first and second instructions are examined to determine their sources and destinations. The written on bit of the first instruction is set to a “written on” state if the destinations of the first and second instructions are the same while a used bit of the first instruction is set to a “used” state if the source of the second instruction is the destination of the first instruction. Thereafter, a priority of the first instruction can be determined from the written on and used bits.

Abstract: A microprocessor is for detecting an interrupt request during execution of a program, saving contextual data elements of the program being executed, sending an interrupt acknowledge signal, and jumping to an interrupt subroutine if the interrupt request is still present after saving the contextual data. Otherwise, the microprocessor resumes execution of the interrupted program.

Abstract: A data processing system is provided with a digital signal processor which has an instruction for conditionally branching based on the contents of a specified test register. Each time a branch is taken, the register is decremented as a side effect of executing the branch instruction. In addition, a predicate register is specified by the instruction. A branch occurs only if both registers meet specified conditions.

Abstract: A processor that efficiently obtains target path instructions in the presence of tight program loops includes at least one execution unit for executing instructions and instruction sequencing logic that supplies instructions to the at least one execution unit for execution. The instruction sequencing logic includes an instruction fetch buffer and a branch prediction unit including a branch target cache. In response to prediction of a branch instruction as taken, the branch target cache causes multiple copies of a target instruction group to be loaded into the instruction fetch buffer under the assumption that the branch instruction is a member of the target instruction group. Thereafter, the branch target cache causes all but one of the multiple copies to be canceled from the instruction fetch buffer prior to dispatch if the branch instruction does not belong to the target instruction group.

Abstract: A processor is provided that is a programmable digital signal processor (DSP) with variable instruction length, offering both high code density and easy programming. Architecture and instruction set are optimized for low power consumption and high efficiency execution of DSP algorithms, such as for wireless telephones, as well as pure control tasks. A coefficient data pointer is provided for accessing coefficient data for use in a multiply-accumulate (MAC) unit. Monitoring circuitry determines when the coefficient data pointer is modified (step 1104). When an instruction is executed (step 1102) that requires a coefficient datum from memory in accordance with the coefficient data pointer, a memory access is inhibited (step 1108) if the coefficient data pointer has not been modified since the last time a memory fetch was made in accordance with the coefficient data pointer and the previously fetched coefficient datum is reused.

Abstract: A method and system for utilizing bits in a collection of illegal op codes in order to enable pre-decoded instructions to be stored in an instruction cache without increasing the number of bits required to represent the pre-decoded instructions. Upon fetching an instruction from memory, the op code is examined for membership in a collection of illegal op codes. If the instruction op code is a member of this collection, the instruction may be re-encoded to use a different, common illegal op code. If the instruction op code is not a member of the collection of illegal op codes, but is instead an instruction to be stored in the instruction cache in a pre-decoded format, the additional pre-decoded information may be stored in the instruction encoding by utilizing the portion of the op code space which has been vacated by the re-encoding of the illegal op codes.

Abstract: A processor supports at least two different state save formats. Each format stores state in the form that the state exists in one or more operating modes of the processor. The operand size of the state save and state restore instructions may be used to indicate which state format is assumed by the processor during execution of the state save and state restore instructions. In one implementation, the processor implements a processor architecture compatible with the x86 architecture with enhancements to support 64 bit addressing and processing. In modes in which 64 bit addressing is supported, segmentation is not used. In 32 bit and 16 bit modes, segmentation is used. Thus, the address of a floating point instruction and/or operand may be indicated by a segment selector or pointer or by a pointer only.

Abstract: The problem identified above is addressed in large part by a microprocessor as disclosed herein. The microprocessor includes a dispatch unit configured to receive a set of instructions from an instruction cache and to forward the set of instructions to an issue queue when the instructions are ready for execution. The dispatch unit may include sampling logic that is configured to select one of the instructions for performance monitoring from the set of instructions. The microprocessor further includes a performance monitor unit enabled to monitor performance characteristics of the selected instruction as it executes. The sampling logic may identify the instruction selected for monitoring as the instruction occupying an eligible position within the set of instructions. The eligible position from which the monitored instruction is selected may vary with each subsequent set of instructions.