Arm Limited

Michael John Gibbs

John Michael Horley

Paul Anthony Gilkerson

Simon John Craske

Michael John Williams

Thomas Christopher Grocutt

François Christopher Jacques Botman

Paul Gilkerson

An apparatus and method are provided for generating and processing a trace stream indicative of instruction execution by processing circuitry. An apparatus has an input interface for receiving instruction execution information from the processing circuitry indicative of a sequence of instructions executed by the processing circuitry, and trace generation circuitry for generating from the instruction execution information a trace stream comprising a plurality of trace elements indicative of execution by the processing circuitry of instruction flow changing instructions within the sequence. The sequence may include a branch behaviour setting instruction that indicates an identified instruction within the sequence, where execution of the branch behaviour setting instruction enables a branch behaviour to be associated with the identified instruction that causes the processing circuitry to branch to a target address identified by the branch behaviour setting instruction when the identified instruction is encountered in the sequence. The trace generation circuitry is further arranged to generate, from the instruction execution information, a trace element indicative of execution behaviour of the branch behaviour setting instruction, and a trace element to indicate that the branch behaviour has been triggered on encountering the identified instruction within the sequence. This enables a very efficient form of trace stream to be used even in situations where the instruction sequence executed by the processing circuitry includes such branch behaviour setting instructions.

Apparatus and method for generating and processing a trace stream indicative of instruction execution by processing circuitry

An apparatus has an input interface for receiving instruction execution information from processing circuitry, and trace generation circuitry for generating from the instruction execution information a trace stream. The instruction sequence from the processing circuitry includes at least one branch-future instruction that effectively turns an instruction identified by the branch-future instruction into a branch, and in particular causes the processing circuitry to branch to a target address identified by the branch-future instruction when that identified instruction is encountered within the instruction sequence. A branch control cache is used to store branch control information derived from the branch-future instruction, and the trace generation circuitry is arranged to detect, based on that branch control information, when the identified instruction has been encountered by the processing circuitry, and upon such detection to then issue within the trace stream a trace element to indicate that a branch to the target address has occurred.

A trace module has monitoring circuitry for monitoring processing of instructions by processing circuitry, and trace output circuitry for outputting a sequence of elements indicative of outcomes of the processing of instructions by the processing circuitry. The trace module supports output of a commit window move element indicating that a commit window, representing a portion of the trace stream comprising at least one speculative element representing at least one speculatively executed instruction, should move while the oldest remaining speculative element of the trace stream remains uncommitted. This can be useful for tracing of transactional memory functionality within program code.

Commit window move element

An apparatus for combining trace data from a plurality of trace sources has an input interface to receive the trace data, and an output interface to output a trace stream. A network of interconnected funnel elements combines the trace data to produce the trace stream. Each funnel element has an output port and a plurality of input ports arranged to receive trace data either from one of the trace sources, or from an output port of another funnel element in the network, and associated control circuitry to control connection of the input ports to the output port. The control circuitry determines control data indicative of a number of trace sources whose trace data is to be routed through each of the input ports of said funnel element, and controls the timing allocation of the associated funnel element's output port to each input port in dependence on the control data.

Apparatus and method for combining trace data from a plurality of trace sources

A processing circuit is responsive to at least one conditional instruction to perform a conditional operation in dependence on a current value of a subset of at least one condition flag. A trace circuit is provided for generating trace data elements indicative of operations performed by the processing circuit. When the processing circuitprocesses at least one selected instruction, then the trace circuit generates a trace data element including a traced condition value indicating at least the subset of condition flags required to determine the outcome of the conditional instruction. A corresponding diagnostic apparatus uses the traced condition value to determine a processing outcome of the at least one conditional instruction.

Processing apparatus, trace unit and diagnostic apparatus

A trace unit, diagnostic apparatus and data processing apparatus are provided for tracing of conditional instructions. The data processing apparatus generates instruction observed indicators indicating execution of conditional instructions and result output indicators indicating output by the data processing apparatus of results of executing respective conditional instructions. The instruction observed indicators and result output indicators are received by a trace unit that is configured to output conditional instruction trace data items and independently output conditional result trace data items enabling separate trace analysis of conditional instructions and corresponding conditional results by a diagnostic apparatus. The instruction observed indicator is received at the trace unit in a first processing cycle of the data processing apparatus while result output indicator is received at in a second different processing cycle.

Tracing of a data processing apparatus

A data processing apparatus is provided with trace circuitry for generating a plurality of trace streams including an instruction trace streamand a data trace stream. The instruction elements within the instruction trace stream and the data elements within the data trace stream are marked with key values KV such that a match may be made between data elements and corresponding instruction elements. When predetermined conditions are met, synchronization markersare inserted in both the instruction trace streamand the data trace streamin order to permit a precise correlation to be made between the instruction elements and the data elements when the data is subsequently analyzed.

Correlating trace data streams

A data processing apparatus is provided comprising prediction circuitry for predicting a response of the data processing circuitry at at least one given execution point to execution of a program instruction; tracing circuitry for tracing operation of the data processing apparatus for outputting a prediction indicator indicating whether or not the predicted response is correct; a data store configured to store information relating to the predicted response of said data processing circuitry at the given execution point for use by at least one of said prediction logic and said tracing circuitry a later execution point; and a history buffer configured to store historical information with regard to one or more entries of the data store at a corresponding execution point previous to the given execution point to enable restoration of said data store to a state corresponding to said previous execution point.

System for efficiently tracing data in a data processing system

A processing circuitis responsive to at least one conditional instruction to perform a conditional operation in dependence on a current value of a subset of at least one condition flag. A trace circuitis provided for generating trace data elements indicative of operations performed by the processing circuit. When the processing circuitprocesses at least one selected instruction, then the trace circuitgenerates a trace data element including a traced condition value indicating at least the subset of condition flagsrequired to determine the outcome of the conditional instruction. A corresponding diagnostic apparatususes the traced condition value to determine a processing outcome of the at least one conditional instruction.

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Stapleford, United Kingdom

Michael John Gibbs