On Tuesday, 20 May 2014 at 09:45:12 UTC, Dominikus Dittes Scherkl
wrote:
On Sunday, 18 May 2014 at 21:58:54 UTC, bearophile wrote:
I presume some ways to improve it are to add to core.bitop
some D standard intrinsics to detect overflows and carry, to
increase run-time performance to sufficient levels. If they
are not fast, people will be less willing to used them.
I'm implementing a "safeSigned" type (which uses the bad
asymmetric min value of signed types as "NaN"), but one
side-product is a somewhat useful function to check for
overflow (it doesn't throw, instead the result will be T.max
for unsigned arguments or T.min for signed arguments). It
doesn't create much overhead and is very easy to do:
T saveOp(string op, T)(T x, T y) pure @save @nogc
if(isIntegral!T && (op=="+" || op=="-" || op=="<<" || op=="*"))
{
mixin("x "~op~"= y");
static if(isSigned!T)
{
static if(op == "*")
{
asm naked { jnc opok; }
}
else
{
asm naked { jno opok; }
}
x = T.min;
}
else // unsigned
{
asm naked { jnc opok; }
x = T.max;
}
opok:
return x;
}
Interesting.
You have a typo: @save instead of @safe
You should also guard the use of asm to x86 architectures only
with version.
