[Webkit-unassigned] [Bug 151315] If B3->Air lowering moves a child to the result tmp when using an Inst with a x86-style UseDef operand, then other uses of that child should also use the result tmp
bugzilla-daemon at webkit.org
bugzilla-daemon at webkit.org
Mon Nov 16 12:21:05 PST 2015
https://bugs.webkit.org/show_bug.cgi?id=151315
--- Comment #3 from Filip Pizlo <fpizlo at apple.com> ---
Whoa, our register allocator already does the magically correct thing. This is Ben's comment:
// We do not want the Use() of this move to interfere with the Def(), even if it is live
// after the Move. If we were to add the interference edge, it would be impossible to
// coalesce the Move even if the two Tmp never interfere anywhere.
This is the verbiage in the IRC paper:
Move instructions are given special consideration. It is important not to create
artifical interferences between the source and destination of a move. Consider the
program:
t := s
...
x := ... s ... ...
y := ... t ...
; copy
; use of s
; use of t
After the copy instruction both s and t are live, and an interference edge would be
added between s and t, since t is being defined at a point where s is live. The
solution is to temporarily remove s from the live set and continue.
--
You are receiving this mail because:
You are the assignee for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.webkit.org/pipermail/webkit-unassigned/attachments/20151116/a0db5728/attachment.html>
More information about the webkit-unassigned
mailing list