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<html><head><link rel="stylesheet" href="style.css"></head><body><div class="page">
<h1>20160706 - Low Cost Branching to Factoring Out Loop Exit Check</h1>
<br>
Threading to hide pipeline depth combined with an ISA which makes branching cheep is one goal.
Specifically absolute branching with immediate destination in the opcode word
(single word branch/call, no adder), and instructions which include a return flag (make returns free).
Enables easy computed branches, both for jump tables, and loops.
Can factor out loop check into hierarchical call tree,
<br>
<br><tt>
Do4: Unroll work four times; Return;<br>
Do16: Call Do4; Call Do4; Call Do4; Jump Do4;<br>
Do64: Call Do16; Call Do16; Call Do16; Jump Do16;<br>
... etc ...
</tt><br>
<br>
Can use a computed branch to jump into the tree for other loop counts.
</div></body></html>