Method for predictive decoding of a load tagged pointer instruction
View Patent ↗Predictive decoding is achieved by fetching an instruction, accessing a predictor containing predictor information including prior instruction execution characteristics, obtaining predictor information for the fetched instruction from the predictor; and generating a selected one of a plurality of decode operation streams corresponding to the fetched instruction. The decode operation stream is selected based on the predictor information.
1. A method for predictive decoding comprising:
fetching a load tagged pointer instruction, the load tagged pointer instruction comprising an associated pointer, the pointer having an associated tag and an associated indicator;
accessing a predictor containing predictor information for the fetched load tagged pointer instruction including prior instruction execution characteristics;
obtaining the predictor information for the fetched load tagged pointer instruction from the predictor;
determining whether the predictor information indicates a null value or a non-null value for the pointer associated with the load tagged pointer instruction;
analyzing a predictor confidence in response to determining that the predictor information indicates a null value for the pointer associated with the load tagged pointer instruction, wherein analyzing the predictor confidence comprises:
generating a safe decode sequence in response to determining that the predictor confidence is weak; and
generating a fast null decode sequence in response to determining that the predictor confidence is strong; and
generating a fast decode sequence in response to determining that the predictor information indicates a non-null value for the pointer associated with the load tagged pointer instruction.
2. The method of claim 1 , wherein generating the fast null decode sequence in response to determining that the predictor confidence is strong further comprises: executing the fast null decode sequence; determining whether the predictor information indicating a null value for the pointer associated with the load tagged pointer instruction is correct based on the execution, and, in response to determining that the predictor information is incorrect, causing a pipeline flush.
3. The method of claim 1 , wherein generating the fast decode sequence in response to determining that the predictor information indicates a non-null value for the pointer associated with the load tagged pointer instruction further comprises: executing the fast decode sequence; determining whether the predictor information indicating a non-null value for the pointer associated with the load tagged pointer instruction is correct based on the execution, and, in response to determining that the predictor information is incorrect, causing a pipeline flush.