[Bug tree-optimization/55213] New: vectorizer ignores __restrict__

[vincenzo.innocente at cern dot ch]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55213



             Bug #: 55213

           Summary: vectorizer ignores __restrict__

    Classification: Unclassified

           Product: gcc

           Version: 4.8.0

            Status: UNCONFIRMED

          Severity: enhancement

          Priority: P3

         Component: tree-optimization

        AssignedTo: unassig...@gcc.gnu.org

        ReportedBy: vincenzo.innoce...@cern.ch





I raised this issue before, still I think that with vectorization becoming more

and more common aliasing starts to become an issue for both code-size and

speed.



for all the loops below the compiler emits alias checks.

My desire would be that foo produces optimal code (possibly with much less

__restrict__ in the code than what I used below), 

still even in the others functions __restrict__ is ignored



compiled as

c++ -Ofast -c soa.cc -std=gnu++11 -ftree-vectorizer-verbose=1 -Wall

-march=corei7

with gcc version 4.8.0 20121028 (experimental) [trunk revision 192889] (GCC) 



#include<cstdint>

struct Soa {



  uint32_t * mem;

  uint32_t ns;

  uint32_t cp;

  int const * __restrict__   i() const  __restrict__ { return (int const*

__restrict__)(mem);}

  float const * __restrict__ f() const  __restrict__ { return (float const*

__restrict__)(mem+cp);}

  float const * __restrict__ g() const  __restrict__ { return (float const*

__restrict__)(mem+2*cp);}



};





void foo(Soa const &  __restrict__  soa, float * __restrict__ res) {

  for(std::size_t i=0; i!=soa.ns; ++i)

    res[i] = soa.f()[i]+soa.g()[i];

}



void bar(Soa const & __restrict__ soa, float * __restrict__ res) {

  float const * __restrict__ f = soa.f(); float const * __restrict__ g =

soa.g();

  int n = soa.ns; for(int i=0; i!=n; ++i)

    res[i] = f[i]+g[i];

}





inline

void add(float const * __restrict__ f, float const * __restrict__ g,float *

__restrict__ res,int n) {

  for(int i=0; i!=n; ++i)

    res[i] = f[i]+g[i];

}



void add(Soa const & __restrict__ soa, float * __restrict__ res) {

   add(soa.f(),soa.g(),res,soa.ns);

}