Methods, apparatus, and processors for packing multiple iterations of loop in a loop buffer

A processor comprising:

• a fetch unit configured to identify and mark a start and an end of a loop in an instruction stream;
• a loop buffer comprising a plurality of rows, each of said rows comprising a plurality of entries;
• and
• a loop buffer control unit coupled to the loop buffer, wherein the loop buffer control unit is configured to detect a loop in an instruction stream;
• wherein the loop buffer is configured to:
• store an iteration of the loop, whereby a first entry of a row of the loop buffer is selected to store a start of the loop;
• in response to determining a last operation of a loop iteration has been written to the loop buffer:
• store another iteration of the loop in the loop buffer, in response to determining the loop buffer is not at least halfway full;
• discontinue storing iterations of the loop in the loop buffer even though a remaining capacity of the loop buffer is adequate to store one or more additional iterations of the loop, in response to determining the loop buffer is at least halfway full;
• store an end of the loop in an entry of a given row of the loop buffer;
• stall after detecting the end of the loop, such that one or more entries of the given row remain unfilled;
• and
• dispatch instructions of the multiple iterations of the loop responsive to the processor entering a loop buffer mode.

A method comprising:

• detecting a loop candidate in an instruction stream;
• determining the loop candidate meets the criteria for buffering in a loop buffer, the loop buffer comprising a plurality of rows, each of said rows comprising a plurality of entries;
• writing a first iteration of the loop candidate to the loop buffer;
• storing a given instruction in a rightmost entry of a row;
• determining whether the given instruction is a backward taken branch;
• in response to determining the given instruction is not a backward taken branch and the loop buffer is not at least halfway full, cause one or more additional iterations of the loop to be written to the loop buffer;
• in response to determining the given instruction is a backward taken branch, prevent additional iterations of the loop from being written to the loop buffer;
• and
• dispatching all entries in a given row of the buffer concurrently.