_Simd [_Safelen(constant-expression)][_Reduction (reduction-identifier : list)] 

for _Simd (int i=0; i<10; i++){
  // loop body
}

Omission of the
private
and
lastprivate
clauses of the
simd
pragma construct because C and C++ already have variable-scoping rules that allow a programmer to cleanly declare a private variable within the scope of a loop iteration
The
linear
clause is omitted because the ability to increment multiple variables makes it unnecessary. See the following example:

float add_floats(float *a, float *b, int n){
  int i=0;
  int j=0;
  float sum=0;

  for _Simd _Reduction(+:sum) (i=0; i<n; i++, j+=2){
    a[i] = a[i] + b[j];
    sum += a[i];
  } 
  return sum;
}

The countable loop for the _Simd keyword has to conform to the for-loop style of an OpenMP* canonical loop form except that multiple variables may be incremented in the incr-expr (See the OpenMP* specification at www.openmp.org).
The loop control variable must be a signed integer type.
The vector values should be signed 8-, 16-, 32-, or 64-bit integers, single or double-precision floating point numbers, or single or double-precision complex numbers.
You cannot use any control constructs to jump into or out of a SIMD loop. That includes the
break
,
return
,
goto
, and
throw
constructs.
A SIMD loop may contain another loop (
for
,
while
,
do
-
while
) in it, but
goto
out of such inner loops is not supported. You may use
break
and
continue
with the inner loop.
A SIMD loop performs memory references unconditionally. Therefore, all address computations must result in valid memory addresses, even though such locations may not be accessed if the loop is executed sequentially