struct Foo

{

  void func3();

  void func4();

  std::vector<float> v;

  float f;

};

​

// will not vectorise

void Foo::func3()

{

  // this->v.end() !!

  for(std::vector<float>::iterator it = v.begin(); it != v.end(); ++it)

  {

    *it *= f;  // this->f !!

  }

}

​

void Foo::func4()

{

  // you need to take a local copy of v.end(), and 'f'.

  const float temp = f;

  for(std::vector<float>::iterator it = v.begin(), e = v.end(); it != e; ++it)

  {

    *it *= temp;

  }

}

#include <vector>

#include <cmath>

​

// fails to vectorise in Visual C++ and /O2

void func1(std::vector<float>& v)

{

  for(size_t i = 0; i < v.size(); ++i)

  {

    v[i] = std::sqrt(v[i]);

  }

}

​

// this will vectorise with sqrtps

void func2(std::vector<float>& v)

{

  for(std::vector<float>::iterator it = v.begin(), e = v.end(); it != e; ++it)

  {

    *it = std::sqrt(*it);

  }

}

-Rpass-missed=loop-vectorize

  -Rpass-analysis=loop-vectorize