Threaded code: Difference between revisions

Revision as of 18:18, 20 May 2021

Revision as of 05:33, 4 August 2021

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==Branches==

In all interpreters, a branch simply changes the thread pointer (<code>ip</code> above) to a different address in the thread. A conditional jump-if-zero branch, tothat jumpjumps only if the top-of-stack value is zero, mightcould be encodedimplemented as followsshown below. NoteThis thatexample uses the embedded parameter version of direct threading so the <code>&thread[123]</code> line is the ___locationdestination toof whichwhere to jump, notif the addresscondition ofis atrue, handler. So,so it must be skipped (<code>ip++</code>) regardlessover of whetherif the branch is not taken.

<syntaxhighlight lang="c">

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...

brz:

when_true_ip = *ip++ // Get destination address for branch

tmp = ip++

if (*--sp == 0) // Pop/Consume top of stack and check if it's zero

if (*sp++ == 0)

ip = tmpwhen_true_ip

jump *ip++

</syntaxhighlight>