Method and apparatus for annotating operands in a computer system with source instruction identifiers

In a computer system having an instruction store for storing instructions and instruction execution means for executing the instructions, instruction processing means for fetching instructions from the instruction store for execution comprising:

• means for processing a source instruction for updating an output operand, means for processing an instruction loop including,
• a target instruction which uses the output operand,
• a loop-back branch instruction for branching so that said target instruction is executed for each iteration of the loop,
• annotation store means for storing annotations associated with said output operand, each annotation including a source instruction identifier for said source instruction, said annotation including a history of executions of branch instructions, including a history of taken branches and not-taken branches taken after said output operand was last updated, said branch instructions including said loop-back branch instruction,
• updating means operating for each update of said output operand to update the source instruction identifier in the annotation and operating for each execution of said branch instructions to update said branch history,
• means for establishing flows for mapping associations between said target instruction, said output operand and said source instruction,
• means for establishing a conditional flow from said loop-back branch instruction to said target instruction if the history in the annotation store means indicates that the last execution of a branch instruction was said loop-back branch instruction in which the branch was taken after said output operand was last updated.

In a computer system having an instruction store for storing instructions and instruction execution means for executing the instructions, instruction processing means for fetching instructions from the instruction store for execution comprising:

• means for processing a source instruction for updating an output operand,
• means for processing an instruction loop including,
• one or more loop instructions,
• a loop-back branch instruction for branching so that said loop instructions are executed for each iteration of the loop,
• means for processing a target instruction which uses the output operand,
• annotation store means for storing annotations associated with said output operand, each annotation including a source instruction identifier for said source instruction, said annotation including a history of executions of branch instructions, including a history of taken branches and not-taken branches taken after said output operand was last updated, said branch instructions including said loop-back branch instruction,
• updating means operating for each update of said output operand to update the source instruction identifier in the annotation and operating for each execution of said branch instructions to update said branch history,
• means for establishing flows for mapping associations between said target instruction, said output operand and said source instruction,
• means for establishing a flow from said source instruction to said target instruction if the history in the annotation store means indicates that the last execution of a branch instruction was said loop-back branch instruction in which the branch was not-taken after said output operand was last updated and if said loop-back branch instruction branches to a branch-to instruction that is after said source instruction.

In a computer system having an instruction store for storing instructions, instruction fetching means for fetching instructions from the instruction store, and instruction execution means for executing the instructions, an instruction processing means comprising:

• means for processing a source instruction for updating an output operand,
• means for processing one or more intervening instructions,
• means for processing a branch-forward branch instruction for branching so that said intervening instructions are conditionally bypassed,
• means for processing a target instruction which uses said output operand,
• annotation store means for storing annotations associated with said output operand, each annotation including a source instruction identifier for said source instruction, said annotation including a history of executions of branch instructions, including a history of taken branches and not-taken branches taken after said output operand was last updated, said branch instructions including said branch-forward branch instruction,
• updating means operating for each update of said output operand to update the source instruction identifier in the annotation and operating for each execution of said branch instructions to update said branch history,
• means for establishing flows for mapping associations between said target instruction, said output operand and said source instruction,
• means for establishing a flow from said source instruction to said target instruction if the history in the annotation store means indicates that the last execution of a branch instruction was said branch-forward branch instruction in which the branch was not-taken after said output operand was last updated and if said branch-forward branch instruction branches to a branch-to instruction that is said target instruction or is before said target instruction.

In a computer system having an instruction store for storing instructions and instruction execution means for executing the instructions, instruction processing means for fetching instructions from the instruction store for execution comprising:

• means for processing a source instruction for updating an output operand,
• means for processing a target instruction which uses said output operand,
• means for processing a branch-forward branch instruction for branching so that said target instruction is conditionally bypassed,
• annotation store means for storing annotations associated with said output operand, each annotation including a source instruction identifier for said source instruction, said annotation including a history of executions of branch instructions, including a history of taken branches and not-taken branches taken after said output operand was last updated, said branch instructions including said branch-forward branch instruction,
• updating means operating for each update of said output operand to update the source instruction identifier in the annotation and operating for each execution of said branch instructions to update said branch history,
• means for establishing flows for mapping associations between said target instruction, said output operand and said source instruction,
• means for establishing a conditional flow from said source instruction to said target instruction if the history in the annotation store means indicates that the last execution of a branch instruction was said branch-forward branch instruction in which the branch was not-taken after said output operand was last updated and if said branch-forward branch instruction branches to a branch-to instruction that is after said target instruction.