memcpy from one blob to another using enoki about enoki

[wjakob]

I took a look. Basically we are at the whims of GCC here, which can generate any kind of code to realize this assignment (in contrast to most other Enoki ops, assignment does not involve an intrinsic). You may be able to do something more explicit by getting pointers and using enoki::store. Note that (as I've often found to be the case) Clang fares better.

[wjakob]

It's indeed odd. Is this on MSVC, and do you specify /AVX2?

[skgbanga]

This is gcc on rhel7 at O3 on a skylake machine. I have verified that is supports AVX2.

[wjakob]

What compiler options did you use to generate this binary?

[skgbanga]

Hi @wjakob

This is the program that I am running:

#include "enoki/dynamic.h"
#include <cassert>

void bar(const char* src, int src_size, char* dst, int dst_size) {
  assert(src_size == dst_size);
  (void)dst_size;

  for (int i = 0; i < src_size; ++i) {
    *dst++ = *src++;
  }
}

void foo(const char* src, int src_size, char* dst, int dst_size) {
  using Array = enoki::Array<int, 16>;

  auto es = enoki::DynamicArray<Array>::map(src, src_size);
  auto ed = enoki::DynamicArray<Array>::map(dst, dst_size);
  for (int i = 0; i < (int)es.packets(); ++i) {
    const auto& pkt = es.packet(i);
    auto& dst_pkt = ed.packet(i);
    dst_pkt = pkt;
  }
}

int main() {}

I compile this via:

g++ -std=c++17 -I contrib/enoki/include/ -O3 -march=skylake main.cpp

I am on a broadwell machine. (checked via

gcc -march=native --help=target -Q | grep arch

)