Processor with improved history file mechanism for restoring processor state after an exception
AssigneeInternational Business Machines Corporation
InventorsBrian King Flacks, Harm Peter Hofstee, Osamu Takahashi
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Abstract
A pipelined processor and method are disclosed including an improved history file unit. The pipelined processor processes a plurality of instructions in order. A register file is included which includes a different read port coupled to each register field in an instruction buffer for reading data from the register file. A history file unit is included and is coupled to each of the read ports of the register file for receiving a copy of all data read from the register file.
Claims13
A processor for processing a plurality of instructions, said processor comprising:
- a register file including a different read port coupled to each register field in an instruction buffer for reading data from said register file;
- and
- a history file unit coupled to each of said read ports of said register file for receiving a copy of all data read from said register file, wherein said history file comprises:
- a first level forwarding multiplexer and a second level forwarding multiplexer for forwarding data to a file storage unit;
- and
- a latch coupled between said first level forwarding multiplexer and said second level forwarding multiplexer, wherein said latch receives as its input an output of said first level forwarding multiplexer, and said latch provides an output that is received as an input to said second level forwarding multiplexer.
A method in a pipelined processor for providing an efficient response to an exception, said method comprising:
- reading data stored in a register file at the time an instruction is being stored in an instruction buffer, said register file including a different read port coupled to each register field in said instruction buffer;
- storing said data in a storage unit of a history file unit that is coupled to each of said read ports of said register file, wherein said history file unit comprises:
- said storage unit;
- a first level forwarding multiplexer and a second level forwarding multiplexer for forwarding data to a file storage unit;
- and
- a latch coupled between said first level forwarding multiplexer and said second level forwarding multiplexer, wherein said latch receives as its input an output of said first level forwarding multiplexer, and said latch provides an output that is received as an input to said second level forwarding multiplexer;
- and
- when an exception occurs within the processor, forwarding said data stored in said storage unit of said history file to said register file.
Dependencies are inferred from the claim text.