[lld] r276323 - [ELF] - Basic support of linkerscript commands: DATA_SEGMENT_ALIGN, DATA_SEGMENT_END, CONSTANT

[Rafael Espíndola via llvm-commits]

> +  // Documentations says there are two ways to compute
> +  // the value of DATA_SEGMENT_ALIGN command, depending on whether the second
> +  // uses fewer COMMONPAGESIZE sized pages for the data segment(area between the
> +  // result of this expression and `DATA_SEGMENT_END') than the first or not.
> +  // That is possible optimization, that we do not support, so we compute that
> +  // function always as (ALIGN(MAXPAGESIZE) + (. & (MAXPAGESIZE - 1))) now.
> +  if (Tok == "DATA_SEGMENT_ALIGN") {
> +    expect("(");
> +    uint64_t L = parseExpr();
> +    expect(",");
> +    parseExpr();
> +    expect(")");
> +    return alignTo(Dot, L) + (Dot & (L - 1));
> +  }

I would suggest using the other expression.

(ALIGN(maxpagesize)
           + ((. + commonpagesize - 1) & (maxpagesize - commonpagesize)))

simplifies to just ALIGN(maxpagesize) with just one page size, which
is exactly what we do on the non script case: Immediately align the
address, possibly wasting disk space, but using the smallest number of
run time pages.

Cheers,
Rafael