added a test for the algorithm introduced for MTRRs

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@24451 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/tests/system/kernel/mtrr_power_test.c

@@ -0,0 +1,85 @@
+#include <stdio.h>
+#include <stdbool.h>
+
+#define uint64 long long unsigned
+#define int64 long long
+
+static void
+nearest_powers(uint64 value, uint64 *lower, uint64 *upper)
+{
+        uint64 power = 1UL << 12;
+	if (lower)
+	        *lower = power;
+        while (value >= power) {
+		if (lower)
+	             *lower = power;
+             power <<= 1;
+        }
+	if (upper)
+	       *upper = power;
+}
+
+
+int64 sols[5];
+int solCount;
+int64 props[5];
+
+static void
+find_nearest(uint64 value, int iteration)
+{
+	if (iteration > 4 || (iteration + 1) >= solCount)
+		return;
+	uint64 down, up;
+	int i;
+	nearest_powers(value, &down, &up);
+	props[iteration] = down;
+	if (value - down < 0x100000) {
+		for (i=0; i<=iteration; i++)
+			sols[i] = props[i];
+		solCount = iteration + 1;
+		return;
+	}
+	find_nearest(value - down, iteration + 1);
+	props[iteration] = -up;
+	if (up - value < 0x100000) {
+		for (i=0; i<=iteration; i++)
+			sols[i] = props[i];
+		solCount = iteration + 1;
+		return;
+	}
+	find_nearest(up - value, iteration + 1);
+}
+
+int
+main()
+{
+	uint64 length = 0xbfee0000; // 0xdfee0000; // 0x9ffb0000; //0xa7f00000; //0x70000000; //0xbfee0000;
+	uint64 base = 0;
+	solCount = 5;
+	find_nearest(length, 0);
+	printf("sols ");
+	int i;
+	for (i=0; i<solCount; i++) {
+		printf("0x%Lx ", sols[i]);
+	}
+	printf("\n");
+
+	bool nextDown = false;
+	for (i = 0; i < solCount; i++) {
+		if (sols[i] < 0) {
+			if (nextDown)
+				base += sols[i];
+			printf("%Lx %Lx %s\n", base, -sols[i], nextDown ? "UC" : "WB");
+			if (!nextDown)
+				base -= sols[i];
+			nextDown = !nextDown;
+		} else {
+			if (nextDown)
+				base -= sols[i];
+			printf("%Lx %Lx %s\n", base, sols[i], nextDown ? "UC" : "WB");
+			if (!nextDown)
+				base += sols[i];
+		}
+		
+	}
+}