On Wednesday, 13 April 2016 at 22:13:27 UTC, Walter Bright wrote:
On 4/12/2016 5:06 AM, Andrei Alexandrescu wrote:
Interesting: http://blog.regehr.org/archives/1384 -- Andrei
Curiously never mentioned is the following optimization:
return a+b*2+27;
becomes:
LEA EAX,27[ESI][EDI*2]
To overflow check:
ADD EDI,EDI
JO overflow
ADD EDI,27
JO overflow
MOV EAX,ESI
ADD EAX,EDI
JO overflow
I don't see efficiency there, even with the JO's being free.
It is clearly not as optimal, but still pretty good. The article
doesn't pretend it all come for free, just that it comes for much
cheaper than before.