Add vector registers to clobber list to prevent compiler optimization.

SME based SGEMMDIRECT kernel uses the vector registers (z) and adding
    clobber list informs compiler not to optimize these registers.

kernel/arm64/sgemm_direct_arm64_sme1.c

@@ -7,7 +7,6 @@
 #include <stdlib.h>
 #include <inttypes.h>
 #include <math.h>
-
 #if defined(HAVE_SME)
 
 /* Function prototypes */
@@ -44,7 +43,17 @@ void CNAME (BLASLONG M, BLASLONG N, BLASLONG K, float * __restrict A,\
         m_mod = ceil((double)M/(double)vl_elms) * vl_elms;
 
         float *A_mod = (float *) malloc(m_mod*K*sizeof(float));
-		
+	    
+	    /* Prevent compiler optimization by reading from memory instead
+	     * of reading directly from vector (z) registers.
+	     * */
+        asm volatile("" : : :"p0", "p1", "p2", "p3", "p4", "p5", "p6", "p7",
+                         "p8", "p9", "p10", "p11", "p12", "p13", "p14", "p15",
+                         "z0", "z1", "z2", "z3", "z4", "z5", "z6", "z7",
+                         "z8", "z9", "z10", "z11", "z12", "z13", "z14", "z15",
+                         "z16", "z17", "z18", "z19", "z20", "z21", "z22", "z23",
+                         "z24", "z25", "z26", "z27", "z28", "z29", "z30", "z31");
+      
         /* Pre-process the left matrix to make it suitable for 
            matrix sum of outer-product calculation
          */
@@ -52,7 +61,13 @@ void CNAME (BLASLONG M, BLASLONG N, BLASLONG K, float * __restrict A,\
         
         /* Calculate C = A*B */
         sgemm_direct_sme1_2VLx2VL(M, K, N, A_mod, B, R);
-        
+       
+        asm volatile("" : : :"p0", "p1", "p2", "p3", "p4", "p5", "p6", "p7",
+                         "p8", "p9", "p10", "p11", "p12", "p13", "p14", "p15",
+                         "z0", "z1", "z2", "z3", "z4", "z5", "z6", "z7",
+                         "z8", "z9", "z10", "z11", "z12", "z13", "z14", "z15",
+                         "z16", "z17", "z18", "z19", "z20", "z21", "z22", "z23",
+                         "z24", "z25", "z26", "z27", "z28", "z29", "z30", "z31");
         free(A_mod);
 }