Hitachi, Ltd.

Renesas Technology Corp.

Tony Lee Werner

Naohiko Irie

Chih-Jui Peng

Sivaram Krishnan

Margaret Rose Gearty

Jackie Andrew Freeman

Sebastian Haviuj Ziesler

Naohiko Irle

A branch control memory store branch instructions which are adapted for optimizing performance of programs run on electronic processors. Flexible instruction parameter fields permit a variety of new branch control and branch instruction implementations best suited for a particular computing environment. These instructions also have separate prediction bits, which are used to optimize loading of target instruction buffers in advance of program execution, so that a pipeline within the processor achieves superior performance during actual program execution.

Branch control memory

A processor is disclosed utilizing improved branch control and branch instructions for optimizing performance of programs run on such processors. Flexible instruction parameter fields permit a variety of new branch control and branch instruction implementations best suited for a particular computing environment. These instructions also have separate prediction bits, which are used to optize loading of target instruction buffers in advance of program execution, so that a pipeline within the processor achieves superior performance during actual program execution.

Processor architecture and operation for exploiting improved branch control instruction

A processor element, structured to execute a 32-bit fixed length instruction set architecture, is backward compatible for executing a 16-bit fixed length instruction set architecture by translating each of the 16-bit instructions into a sequence of one or more 32-bit instructions. The 32-bit instruction set architecture includes &ldquo;prepare to branch&rdquo; instructions that allow target addresses for branch instructions to be set up in advance of the branch. The 32-bit prepare to branch and branch instructions are combined to execute a 16-bit branch instruction coupled with a 16-bit Delay Slot instruction.

Emulating execution of smaller fixed-length branch/delay slot instructions with a sequence of larger fixed-length instructions

A cache system has a multilevel cache architecture. An L1 cache receives instructions from an external memory. An L0 cache has a first predetermined number L0 of cache lines for receiving instructions from the L1 cache. An assist cache has a victim cache and a prefetch cache. The victim cache stores a second predetermined number VC of cache lines, and the prefetch cache stores a third predetermined number PC of cache lines. The victim cache receives instructions from the L0 cache. The prefetch cache receives instructions from the L1 cache. A victim filter stores a fourth predetermined number VF of addresses wherein VF is a function of L0 and a number of cache writes. The number of cache writes to the L0 and the victim cache is reduced relative to using the L0 cache without the assist cache.

Two-level instruction cache for embedded processors

A processor having an execution pipeline and a cache memory including a plurality of cache blocks with instruction words held in selected ones of the cache blocks. An ICBI address buffer is provided for holding addresses of instruction cache blocks to be invalidated by ICBI instructions pending in the processor's execution pipeline. An instruction cache controller coupled to the cache memory generates cache accesses to invalidate specified cache blocks in response to receiving buffered addresses from the ICBI address buffer. Preferably the cache accesses serve to commit ICBI instructions to the instruction cache asynchronously with respect to the processor's execution pipeline.

Mechanism for invalidating instruction cache blocks in a pipeline processor

A processor is provided with an improved instruction buffer, branch target instruction memory, branch target address memory and instruction decoder adapted for handling branch instructions so as to reduce latencies. A branch operation uses both a program branch control instruction (executed in advance to determine the branch target instruction address) and either a conditional or unconditional branch instruction associated with a conditional/unconditional branch target instruction respectively. The conditional/unconditional branch instruction and the program branch control instruction both include separate prediction indicators used by the instruction decoder for initiating a loading and speculatively pre-loading of instructions for execution in the processor.

Indexing branch target instruction memory using target address generated by branch control instruction to reduce branch latency

An improved preload/prefetching architecture is disclosed for controlling branch target instruction loading in a pipelined processor. Branch target instructions can be speculatively preloaded/prefetched based on a first prediction indicator provided in a branch control instruction, and they also can be actually loaded/fetched based on a second prediction indicator provided in a branch instruction. This mechanism results in reduced cache latency during program execution. The preloading/prefetching of branch target instructions can also be prioritized under software control to optimize instruction execution, based on particular indicators specified for branch target instructions within a branch hint buffer.

Growing community of inventors

Santa Clara, CA, United States of America

Tony Lee Werner