int[2][]'s sort are slow with default comparator

[dlangBugzillaToGithub]

Kohei Morita (@yosupo06) reported this on 2016-12-28T15:25:11Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=17039

Description

when I want to sort int[2][], I noticed that if I use my comparator, I can sort more faster.

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import std.stdio, std.array, std.datetime, std.random, std.algorithm;

void main() {
    //make random array
    int[2][] base = new int[2][1000000];
    Random gen = Random(unpredictableSeed);
    foreach (ref d; base) {
        d[0] = uniform(0, 1_000_000_000, gen);
        d[1] = uniform(0, 1_000_000_000, gen);
    }

    //1: simple
    auto b = base.dup;
    StopWatch sw;
    writeln("START");
    sw.start;
    sort(b);
    sw.stop;
    writeln("END ", sw.peek.msecs, "ms (type 1)");
    sw.reset;
    
    //2: my comparator
    auto c = base.dup;
    writeln("START");
    sw.start;
    sort!((l, r){
        foreach (i; 0..2) {
            if (l[i] != r[i]) return l[i] < r[i];
        }
        return false;
    })(c);
    sw.stop;
    writeln("END ", sw.peek.msecs, "ms (type 2)");
    sw.reset;
    
    assert(equal(b, c));
}
------------------------------------------

This code output

START
END 520ms (type 1)
START
END 330ms (type 2)

with dmd(v2.072.1) -O -release source.d

It seem slower about x1.5, is this a bug?