• Per =?UTF-8?B?Tm9yZGzDtnc=?= (8/8) Oct 19 2018 Now that
• Nathan S. (9/17) Oct 20 2018 I looked and identified low-hanging fruit in
• Stanislav Blinov (6/11) Oct 20 2018 Not unless `mem{set, cpy, move}` etc. are made into compiler
• Per =?UTF-8?B?Tm9yZGzDtnc=?= (4/15) Oct 21 2018 So in which cases is `memset` faster than assignment?
• Nathan S. (4/6) Oct 30 2018 I don't know. My guess would be maybe if the type is large, or

Per =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:

Now that

     https://github.com/dlang/phobos/pull/6411

has been merged and DMD stable soon has the new

     __traits(isZeroInit, T)

found here

     https://dlang.org/changelog/2.083.0.html#isZeroInit

are there more zero-initializations that can be optimized in 
std.experimental.allocator?

Nathan S. <no.public.email example.com> writes:

On Friday, 19 October 2018 at 21:29:42 UTC, Per Nordlöw wrote:
 Now that

     https://github.com/dlang/phobos/pull/6411

 has been merged and DMD stable soon has the new

     __traits(isZeroInit, T)

 found here

     https://dlang.org/changelog/2.083.0.html#isZeroInit

 are there more zero-initializations that can be optimized in 
 std.experimental.allocator?

I looked and identified low-hanging fruit in 
std.mutation.initializeAll & moveEmplace and in 


rely on being able to identify if it's ever more efficient to 
write `memset(&x, 0, typeof(x).sizeof)` instead of `x = 
typeof(x).init` which seems like the kind of optimization that 
belongs in the compiler instead.

Stanislav Blinov <stanislav.blinov gmail.com> writes:

On Saturday, 20 October 2018 at 15:10:38 UTC, Nathan S. wrote:

 Other opportunities  would rely on being able to identify if 
 it's ever more efficient to write `memset(&x, 0, 
 typeof(x).sizeof)` instead of `x = typeof(x).init` which seems 
 like the kind of optimization that belongs in the compiler 
 instead.

Not unless `mem{set, cpy, move}` etc. are made into compiler 
intrinsics. Carrying libc dependencies into low-level sensitive 
code just stinks. If anything, the `memcpy` calls should be 
removed from `moveEmplace`, not `memset` calls added to it.
They're also not CTFE-able.

Per =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:

On Saturday, 20 October 2018 at 15:10:38 UTC, Nathan S. wrote:
 are there more zero-initializations that can be optimized in 
 std.experimental.allocator?

 I looked and identified low-hanging fruit in 
 std.mutation.initializeAll & moveEmplace and in 



What did you search for to find these?

 Other opportunities would rely on being able to identify if 
 it's ever more efficient to write `memset(&x, 0, 
 typeof(x).sizeof)` instead of `x = typeof(x).init` which seems 
 like the kind of optimization that belongs in the compiler 
 instead.

So in which cases is `memset` faster than assignment?

Thanks!

Nathan S. <no.public.email example.com> writes:

On Sunday, 21 October 2018 at 11:09:54 UTC, Per Nordlöw wrote:
 What did you search for to find these?

`typeid` and `.init`.

 So in which cases is `memset` faster than assignment?

I don't know. My guess would be maybe if the type is large, or 
maybe never. Certainly we'd have to benchmark.