common/memsize.c: Simplify RAM size detection

The case of memory of size 0 is not that different from a memory of any other
size, so we remove the duplicate code and treat the small differences when it
is the case.

Signed-off-by: Eddy Petrișor <eddy.petrisor@gmail.com>

common/memsize.c

@@ -33,38 +33,28 @@ long get_ram_size(long *base, long maxsize)
 	long           size;
 	int            i = 0;
 
-	for (cnt = (maxsize / sizeof(long)) >> 1; cnt > 0; cnt >>= 1) {
+	for (cnt = (maxsize / sizeof(long)) >> 1; cnt >= 0; cnt >>= 1) {
 		addr = base + cnt;	/* pointer arith! */
 		sync();
-		save[i++] = *addr;
+		save[i] = *addr;
 		sync();
-		*addr = ~cnt;
-	}
-
-	addr = base;
-	sync();
-	save[i] = *addr;
-	sync();
-	*addr = 0;
-
-	sync();
-	if ((val = *addr) != 0) {
-		/* Restore the original data before leaving the function. */
-		sync();
-		*addr = save[i];
-		for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {
-			addr  = base + cnt;
-			sync();
-			*addr = save[--i];
+		if (cnt) {
+			i++;
+			*addr = ~cnt;
+		} else {
+			*addr = 0;
 		}
-		return (0);
 	}
 
-	for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {
+	sync();
+	cnt = 0;
+	do {
 		addr = base + cnt;	/* pointer arith! */
 		val = *addr;
-		*addr = save[--i];
-		if (val != ~cnt) {
+		*addr = save[i--];
+		sync();
+		if (((cnt == 0) && (val != 0)) ||
+		    ((cnt != 0) && (val != ~cnt))) {
 			size = cnt * sizeof(long);
 			/*
 			 * Restore the original data
@@ -74,11 +64,16 @@ long get_ram_size(long *base, long maxsize)
 			     cnt < maxsize / sizeof(long);
 			     cnt <<= 1) {
 				addr  = base + cnt;
-				*addr = save[--i];
+				*addr = save[i--];
 			}
 			return (size);
 		}
-	}
+
+		if (cnt)
+			cnt = cnt << 1;
+		else
+			cnt = 1;
+	} while (cnt < maxsize / sizeof(long));
 
 	return (maxsize);
 }