Add 'smemcoherence' kernel

tests/opencl/smemcoherence/kernel.cl

@@ -0,0 +1,33 @@
+__kernel void smemcoherence (__global volatile const int *src,
+        __global volatile int *dst,
+        __local volatile int *smem,
+		int n)
+{
+    __local volatile int *markers = (__local int *)((__local unsigned char *)smem + 0x1000);
+    int gid = get_global_id(0);
+
+    // assumes total store ordering on smem
+    markers[gid] = 0;
+    smem[gid] = gid;
+    markers[gid] = 1;
+
+    // 0-th thread checks if all threads finished writing
+    if (gid == 0) {
+        int gridsize = get_global_size(0);
+		int retry = 0;
+		for (;; retry++) {
+			for (int i = 0; i < gridsize; i++) {
+				if (markers[i] != 1) {
+					goto try_again;
+				}
+			}
+			break;
+		try_again:;
+		}
+
+		for (int i = 0; i < n; i++) {
+			dst[i] = smem[i];
+		}
+		dst[n] = retry;
+    }
+}