On Thu, 14 Apr 2011 13:36:07 -0400, Timon Gehr <timon.g...@gmx.ch> wrote:
Andrei Mitrovic:
Can the compiler optimize the second case and convert b.front to just
do one field access?
In simple cases, obviously yes:
import std.range;
import std.stdio;
void main(){
int[] a=new int[1000];
auto b=retro(retro(a));
writeln(b.front);
}
Produces:
.text:08094B64 public _Dmain
.text:08094B64 _Dmain proc near ; CODE XREF:
_D2rt6dmain24mainUiPPaZi7runMainMFZv+15%19p
.text:08094B64 push ebp
.text:08094B65 mov ebp, esp
.text:08094B67 mov eax, offset
_D11TypeInfo_Ai6__initZ
.text:08094B6C push 3E8h
.text:08094B71 push eax
.text:08094B72 call _d_newarrayT
.text:08094B77 add esp, 8
.text:08094B7A mov eax, offset
_D3std5stdio6stdoutS3std5stdio4File
.text:08094B7F push dword ptr [edx]
.text:08094B81 push 0Ah
.text:08094B83 call
_D3std5stdio4File14__T5writeTiTaZ5writeMFiaZv
.text:08094B88 xor eax, eax
.text:08094B8A pop ebp
.text:08094B8B retn
.text:08094B8B _Dmain endp ; sp = -8
DMD even recognizes the fact, that edx contains the pointer to the first
element of b.
I do not know about more complex cases, I think it depends on DMD's
inlining caps,
which are (naturally) somewhat poorer than gcc's at the moment.
Nah, it's simpler than that:
assert(is(typeof(b) == int[]));
which is done by retro (it detects if you're retro-ing a retro range, and
just returns the original).
-Steve
