On Sun, 27 Mar 2011 09:37:47 -0400, bearophile <bearophileh...@lycos.com>
wrote:
I have compiled this little D2 program:
int[] foo() {
return [];
}
int[] bar() {
return null;
}
void main() {}
Using DMD 2.052, dmd -O -release -inline test2.d
This is the asm of the two functions:
_D5test23fooFZAi comdat
L0: push EAX
mov EAX,offset FLAT:_D11TypeInfo_Ai6__initZ
push 0
push EAX
call near ptr __d_arrayliteralT
mov EDX,EAX
add ESP,8
pop ECX
xor EAX,EAX
ret
_D5test23barFZAi comdat
xor EAX,EAX
xor EDX,EDX
ret
Is this expected and desired? Isn't it better to compile the foo() as
bar()?
Probably. The runtime that allocates an array looks like this (irrelevant
parts collapsed):
extern (C) void* _d_arrayliteralT(TypeInfo ti, size_t length, ...)
{
auto sizeelem = ti.next.tsize(); // array element size
void* result;
...
if (length == 0 || sizeelem == 0)
result = null;
else
{
...
}
return result;
}
So essentially, you are getting the same thing, but using [] is slower.
-Steve