Altera example matrix multiply produces Compiler warning: non-vectorized load/stores

I am attempting to compile the matrix multiply example located here: https://www.altera.com/support/support-resources/design-examples/design-software/opencl/matrix-multiplication.html

However when compiling I see the following:

aoc: Running OpenCL parser....
/home/mike/ont_core_cpp/ont_core/basecall_nn/ocl/altera_experiments/matrix_mult/device/matrix_mult.cl:105:34: warning: declaring kernel argument with no 'restrict' may lead to low kernel performance
                 __global float *A,
                                 ^
/home/mike/ont_core_cpp/ont_core/basecall_nn/ocl/altera_experiments/matrix_mult/device/matrix_mult.cl:106:34: warning: declaring kernel argument with no 'restrict' may lead to low kernel performance
                 __global float *B, 
                                 ^
2 warnings generated.
aoc: OpenCL parser completed successfully.
aoc: Compiling....
aoc: Linking with IP library ...
Checking if memory usage is larger than 100%
Compiler Warning: Vectorized kernel contains loads/stores that cannot be vectorized. This might reduce performance.
+--------------------------------------------------------------------+
; Estimated Resource Usage Summary                                   ;
+----------------------------------------+---------------------------+
; Resource                               + Usage                     ;
+----------------------------------------+---------------------------+
; Logic utilization                      ;   33%                     ;
; ALUTs                                  ;   18%                     ;
; Dedicated logic registers              ;   16%                     ;
; Memory blocks                          ;   32%                     ;
; DSP blocks                             ;   23%                     ;
+----------------------------------------+---------------------------;

I am compiling with the following options: -v --report --fpc --fp-relaxed -cl-fast-relaxed-math -cl-finite-math-only

This happens with aoc Version 17.0.0 Build 290 and also with aoc Version 16.1.2 Build 203.

The part of the kernel which causes the error appears to be:

       # pragma unroll
        for (int k = 0; k < BLOCK_SIZE; ++k)
        {
            running_sum += A_local * B_local;
        }

But I cannot understand why this would be a problem.