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Non-intrusive software breakpoints in a processor instruction execution pipeline

  • US 6,016,555 A
  • Filed: 11/19/1997
  • Issued: 01/18/2000
  • Est. Priority Date: 11/19/1997
  • Status: Expired due to Term
First Claim
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1. A method for debugging a processor within a data processing system, the processor having an instruction execution pipeline with at least a first pipeline phase followed by a second pipeline phase, comprising the steps of:

  • forming a software breakpoint instruction within a sequence of instructions by replacing a field within an operational instruction with a predetermined breakpoint code;

    fetching and executing a portion of the sequence of instructions in the processor instruction execution pipeline in a normal operational manner to initiate a plurality of overlapping operations in the instruction pipeline;

    fetching and partially executing the software breakpoint instruction in the first pipeline phase of the instruction pipeline;

    halting the normal operation of the instruction pipeline in response to decoding the breakpoint code in the second pipeline phase of the instruction pipeline;

    performing a debug function in response to decoding the breakpoint code; and

    restarting the normal operation of the instruction pipeline after the step of performing a debug function without refetching the operational instruction which was replaced by the software breakpoint instruction in a manner such that the operational instruction is executed as if the field within the operational instruction had not been replaced with the predetermined breakpoint code.

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