[Bug tree-optimization/60510] New: SLP blocks loop vectorization (with reduction)

[kirill.yukhin at intel dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60510

            Bug ID: 60510
           Summary: SLP blocks loop vectorization (with reduction)
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kirill.yukhin at intel dot com

Hello,
This case is not vectorized:
$ cat f2.f
      subroutine foo(a,x,y,n)
      implicit none
      integer n,i

      real*8 y(n),x(n),a

      do i=1,n
         a=a+x(i)*y(i)+x(i)
      enddo

      return
      end

When `+x(i)` removed, vectorization passes.

Compilation: ./build-x86_64-linux/gcc/gfortran -B./build-x86_64-linux/gcc -S
-Ofast -mavx2 f2.f -fno-unroll-loops -fdump-tree-vect-all

vect report says:
f2.f:7:0: note: type of def: 3.
f2.f:7:0: note: vect_is_simple_use: operand _13
f2.f:7:0: note: def_stmt: _13 = _12 + prephitmp_32;

f2.f:7:0: note: type of def: 3.
f2.f:7:0: note: Build SLP for # VUSE <.MEM_2>
_12 = *x_11(D)[_10];

f2.f:7:0: note: Build SLP failed: not grouped load # VUSE <.MEM_2>
_12 = *x_11(D)[_10];