Instruction queue scanning using opcode identification

Details Instruction queue scanning using opcode identification Instruction queue scanning using opcode identification

1997-02-04

1999-04-20

Lall, Parshotam S.

395385, 395388, G06F 938

Patent

active

058965181

ABSTRACT:
A superscalar complex instruction set computer ("CISC") processor (100) having a reduced instruction set computer ("RISC") superscalar core (110) includes an instruction cache (104) which identifies and marks raw x86 instruction start and end points and encodes "pre-decode" information, a byte queue (106) which is a queue of aligned instruction and pre-decode information of the "predicted executed" state, and an instruction decoder (108) which generates type, opcode, and operand pointer values for RISC-like operations (ROPs) based on the aligned pre-decoded x86 instructions in the byte queue. The instruction decoder includes in each dispatch position a logic-based conversion path, a memory-based conversion path, and a common conversion path for converting CISC instructions to ROPs. An ROP multiplexer (400) directs x86 instructions from the byte queue to the conversion paths. The ROP multiplexer includes scan logic (690) which rapidly scans the byte queue to generate for each dispatch position an array of bits (ISELx) that identifies the location of the scan logic is segregated into groups of bit processing logic (GP(x,y)) and includes a look-ahead capability (LAG(x)) between groups.

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