D: vector operation vs manual loop

ldc-O3-release-inline.s

...
movl  $239, %edi
movq	%r14, %rsi
movl	$1, %edx
callq	_arrayExpSliceAddass_k

...

LBB0_14:
    xorl	%eax, %eax
	.align	16, 0x90
.LBB0_15:
	incl	64(%rsp,%rax,4)
	incq	%rax
	cmpq	$239, %rax
	jne	.LBB0_15

test.d

import std.datetime;
import std.stdio;

void main() {

    StopWatch sw;
    uint[1024] array;

    for (size_t k = 0; k < 15; k++)
    {
        array[] = 0;
        sw.start();
        for (size_t i = 0; i < 1000; i++)
            array[0 .. 239] += 1;

        sw.stop();

        write(sw.peek().usecs, "\t");

        array[] = 0;
        sw.reset();
        sw.start();
        for (size_t i = 0; i < 1000; i++)
            for (size_t j = 0; j < 239; j++)
                array[j] += 1;
        sw.stop();

        writeln(sw.peek().usecs);
    }
}