On Saturday, 13 September 2014 at 19:20:51 UTC, Timon Gehr wrote:
On 09/13/2014 09:07 PM, "Marc =?UTF-8?B?U2Now7x0eiI=?=
<schue...@gmx.net>" wrote:
Wouldn't `const` be enough? AFAICS, `immutable` is mostly
useful for
shared data.
const prevents modification, but does not guarantee that no
modification takes place elsewhere. I.e. it enables fewer
program transformations.
But as it is thread-local, is it really relevant (for
optimization)? I can see two situations where it can potentially
matter: pointer parameter aliasing, and calls to
function/delegate calls that might modify a value referenced by a
pointer.
In practice the latter is probably not so important for
optimizations, because the compiler would most likely have a hard
time caching a value across a function call because of register
pressure, so a reload would be necessary anyway. I don't know
about parameter aliasing, but I guess it only makes a difference
in corner cases. In these cases, it's easy to forbid it by
contract (as slice copying does).
