System for processing shift, mask, and merge operations in one instruction

In a data processing system having stored instructions, a local store memory, instruction selection, decoding, and execution circuitry, and addressable storage for storing instructions and operands, a method for processing programmably selectable shift, mask, and merge operations on selected operands specified by one computer instruction, the instruction containing a shift count and a shift direction, said method comprising the steps of:

• a) fetching the instruction from the addressable storage for processing;
• b) decoding a shift/mask/merge command embedded in the fetched instruction;
• c) loading a first operand with data obtained from a first local store memory location specified by the fetched instruction;
• d) loading a mask/merge register with programmably selectable mask and merge indicators obtained from a second local store memory location specified by the fetched instruction, said programmably selectable mask indicators including a plurality of one-bit flags controlling masking of two-bit portions of a mask operand, said programmably selectable merge indicators including a plurality of one-bit flags controlling merging of two-bit portions of merge operands;
• e) selecting one of said first operand or a second operand to be shifted and masked;
• f) shifting said selected operand according to the shift count and the shift direction;
• g) masking the shifted portion of said selected operand according to said programmably selectable mask indicators;
• and
• h) merging the shifted and masked portion of said selected operand, according to said programmably selectable merge indicators, with the unselected operand to produce a merge result.

A system for selectively executing shift, mask, and merge operations on two operands specified by one computer instruction according to a programmably selectable shift count, a programmably selectable shift direction, and programmably selectable mask and merge conditions, comprising:

• a random access local store memory to hold operands for the shift, mask, and merge operations and to hold mask and merge indicators representing the programmably selectable mask and merge conditions, said mask indicators including a plurality of one-bit flags controlling masking of two-bit portions of a mask operand, said merge indicators including a plurality of one-bit flags controlling merging of two-bit portions of merge operands;
• a first register connected to said random access local store memory to hold at least temporarily a first operand to be manipulated, said first operand being selected from said random access local store memory by the computer instruction;
• a second register to hold at least temporarily a second operand to be manipulated;
• an internal communications bus connected to said second register, said internal communications bus providing input data signals to said second register;
• selection circuitry, coupled to said first and said second registers, to alternatively select one of said first and said second registers to be shifted and masked, and then merged with the other register, according to the computer instruction;
• shift circuitry, connected to said selection circuitry, to selectively shift said selected one of said first and said second registers according to the programmably selectable shift count and shift direction;
• a mask/merge register connected to said random access local store memory to hold said mask and merge indicators;
• mask circuitry, connected to said shift circuitry and said mask/merge register, to select a portion of said shifted selected one of said first and said second registers to be merged, by masking said shifted selected one of said first and said second registers according to said mask indicators;
• and
• merge circuitry, connected to said selection circuitry, said mask circuitry and said mask/merge register, to merge said selected portion of said shifted selected one of said first and said second registers with the other register, according to said merge indicators, to produce a merged result.