On Tuesday, 17 December 2013 at 00:53:07 UTC, Walter Bright wrote:
It definitely is a good idea for the compiler to recognize:
if (s == "foo" || s == "bar" || s == "baz")
and generate special code for it.
I guess that would work in this case if among() is inlined since
the integer is then used as a boolean and can be reduced to the
same value (true). If it isn't inlined you would deal with
(pseudo):
r=0;
if(s=="foo"){ r=1; goto e;}
if(s=="bar"){ r=2; goto e;}
if(s=="baz"){ r=3; goto e;}
e:
return r
So it would be more general to optimize conditionals that test
the same (unchanged) variable into a switch() and then if
possible reduce that to a table lookup if each basic block in the
switch sets the same variables to a constant value…
I guess a fast bool variation could be something like (pseudo):
// skip the length test if s[2] on an empty string doesn't
core-dump.
if(s.length<3) return false;
return lut[ (s[2]-'o') & MASK] == s;
(the NNTP server or the web-interface seemed to be dead for 12
hours?)
