On Fri, 07 Aug 2009 15:44:04 -0700, Sergey Gromov <[email protected]>
wrote:
Fri, 07 Aug 2009 13:47:31 -0700, Robert Jacques wrote:
On Fri, 07 Aug 2009 12:03:43 -0700, Yigal Chripun <[email protected]>
wrote:
regarding the div() function above, I was thinking about using D's
naked
asm feature. From what little I know about this, the compiler doesn't
generate the usual asm code for this sort of function to handle
registers, stack, etc, and you're supposed to do everything yourself in
asm.
IIRC naked asm only works for zero-argument and single arguments of size
1,2 or 4 functions, which div is not.
I don't think your comment above about the function call overhead
applies if div is implemented in such a way but I'm no expert and
someone more knowledgeable can shed more light on this. (Don?)
If you check the D ABI, one of the arguments must be passed on the
stack,
the other in a specific register (EAX).
http://www.digitalmars.com/d/2.0/abi.html
So the backend can't do things like ECX = EBX / EDX. Instead it has to
save/restore whatever's in EAX, ECX and EDX before/after the div call.
Inlined functions become integral part of their outer functions and
therefore are not obliged to follow ABI. They don't have prologues,
epilogues, call overhead, etc.
Yes and no. This is quite true for normal D functions, but throwing manual
asm into the mix does mess up register allocation, etc. Even with naked
asm, a minimum three registers must be saved.
Moreover compiler intrinsics are
functions which compiler recognizes and treats specially, usually by
replacing them with a single processor instruction.
We weren't discussing implementation with intrinsics, but as with a
standard library function.
