512640 - nanojit: refactor Assembler::findRegFor()

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Nicholas Nethercote [inactive]]

Attachment: patch

findRegFor() currently involves a hard-to-follow combination of complex control flow and assignments.  This patch refactors it so it's much easier to follow.  I did the refactoring by carefully making a succession of small, mechanical changes, so I'm fairly confident it's correct.  The logic is certainly clearer, esp. that there are four main cases.

There is some repetition in the new version relating to hint() and the registerAlloc()/addActive() pair, but I don't think that's so bad.  (The registerAlloc()/addActive() cases could be cleaned up by better handling of RegAlloc invariants, as mentioned in bug 512634.)  The source code is a little shorter, the binary code is a little longer, and SunSpider speed hasn't changed.

Comment 1

[Nicholas Nethercote [inactive]]

http://hg.mozilla.org/tracemonkey/rev/6c0862612a4a

Comment 2

[Nicholas Nethercote [inactive]]

Follow-up commit to remove a stray debugging printf():

http://hg.mozilla.org/tracemonkey/rev/430c1f40b6cd

Comment 3

[Blake Kaplan (:mrbkap) (inactive)]

http://hg.mozilla.org/mozilla-central/rev/6c0862612a4a

Comment 4

[Blake Kaplan (:mrbkap) (inactive)]

http://hg.mozilla.org/mozilla-central/rev/430c1f40b6cd

Comment 5

[Robert Sayre]

http://hg.mozilla.org/releases/mozilla-1.9.2/rev/386507096392