BCS:
> IIRC DMD doesn't always do the constant folding (Decent has a post processed
> view that shows this in some cases) For instance, IIRC it only does left
> most so this:
> char[] foo = "foo";
> char[] bar = foo ~ "bar" ~ "baz"
> doesn't get folded. And even if DMD were to start doing that one, there is
> no requirement that another compiler also do it.
If there are guarantees that "abc" "def" are folded at compile time, then the
same guarantees can be specified for "abc" ~ "def". I can't see a problem.
I have also compiled this code with DMD:
void main() {
string foo = "foo";
string bar = foo ~ "bar" ~ "baz";
}
Resulting asm, no optimizations:
L0: push EBP
mov EBP,ESP
mov EDX,FLAT:_DATA[0Ch]
mov EAX,FLAT:_DATA[08h]
push dword ptr FLAT:_DATA[01Ch]
push dword ptr FLAT:_DATA[018h]
push dword ptr FLAT:_DATA[02Ch]
push dword ptr FLAT:_DATA[028h]
push EDX
push EAX
push 3
mov ECX,offset FLAT:_D11TypeInfo_Aa6__initZ
push ECX
call near ptr __d_arraycatnT
xor EAX,EAX
add ESP,020h
pop EBP
ret
Resulting asm, with optimizations:
L0: sub ESP,0Ch
mov EAX,offset FLAT:_D11TypeInfo_Aa6__initZ
push dword ptr FLAT:_DATA[01Ch]
push dword ptr FLAT:_DATA[018h]
push dword ptr FLAT:_DATA[02Ch]
push dword ptr FLAT:_DATA[028h]
push dword ptr FLAT:_DATA[0Ch]
push dword ptr FLAT:_DATA[08h]
push 3
push EAX
call near ptr __d_arraycatnT
add ESP,020h
add ESP,0Ch
xor EAX,EAX
ret
I can see just one arraycatn, so the two string literals are folded at compile
time, I think.
Bye,
bearophile
