DMD is faster than LDC and GDC

[Daniel Kozak via Digitalmars-d]

code:

import std.stdio;

auto fmttable(immutable(string[][]) table) {

     import std.array : appender, uninitializedArray;
     import std.range : take, repeat;
     import std.exception : assumeUnique;

     auto res = appender(uninitializedArray!(char[])(128));
     res.clear();

     if (table.length == 0) return "";
     // column widths
     auto widths = new int[](table[0].length);

     foreach (rownum, row; table) {
         foreach (colnum, cell; row) {
             if (cell.length > widths[colnum])
                 widths[colnum] = cast(int)cell.length;
         }
     }

     foreach (row; table) {
         res ~= "|";
         foreach (colnum, cell; row) {
             int l = widths[colnum] - cast(int)cell.length;
             res ~= cell;
             if (l)
                 res ~= ' '.repeat().take(l);
             res ~= "|";
         }
         res.put("\n");
     }

      return res.data.assumeUnique();
}

void main() {

     immutable table = [
         ["row1.1", "row1.2  ", "row1.3"],
         ["row2.1", "row2.2", "row2.3"],
         ["row3.1", "row3.2", "row3.3  "],
         ["row4.1", "row4.2", "row4.3"],
         ["row5.1", "row5.2", "row5.3"],
     ];

     writeln(fmttable(table));
     int i;
     for (i=0; i < 1000000; ++i) {
         fmttable(table);
     }
     writeln(i);
}

timings:

DMD (-O -release -inline -boundscheck=off):
real	0m0.003s
user	0m0.000s
sys	0m0.000s

LDMD2-ldc2 (-O -release -inline -boundscheck=off):
real	0m1.071s
user	0m1.067s
sys	0m0.000s


GDC (-O3 -finline -frelease -fno-bounds-check):
real	0m0.724s
user	0m0.720s
sys	0m0.003s