[Truffle] Implement Fixnum#<<(int) correctly.

* Mostly, there was no case to return an int.
jruby · Oct 30, 2014 · 52de8f1 · 52de8f1
1 parent 816e3e2
commit 52de8f1
Showing 1 changed file with 43 additions and 7 deletions.
diff --git a/core/src/main/java/org/jruby/truffle/nodes/core/FixnumNodes.java b/core/src/main/java/org/jruby/truffle/nodes/core/FixnumNodes.java
@@ -1187,21 +1187,49 @@ public LeftShiftNode(LeftShiftNode prev) {
             fixnumOrBignum = prev.fixnumOrBignum;
         }
 
-        @Specialization
-        public Object leftShift(int a, int b) {
-            return leftShift((long) a, b);
+        @Specialization(guards = "canShiftIntoInt")
+        public int leftShift(int a, int b) {
+            if (b > 0) {
+                bAboveZeroProfile.enter();
+
+                return a << b;
+            } else {
+                bNotAboveZeroProfile.enter();
+                if (-b >= Integer.SIZE) {
+                    return 0;
+                } else {
+                    return a >> -b;
+                }
+            }
+        }
+
+        @Specialization(guards = "canShiftIntoLong")
+        public long leftShift(long a, int b) {
+            if (b > 0) {
+                bAboveZeroProfile.enter();
+
+                return a << b;
+            } else {
+                bNotAboveZeroProfile.enter();
+
+                if (-b >= Long.SIZE) {
+                    return 0;
+                } else {
+                    return a >> -b;
+                }
+            }
         }
 
         @Specialization
-        public Object leftShift(long a, int b) {
+        public Object leftShiftWithOverflow(long a, int b) {
             if (b > 0) {
                 bAboveZeroProfile.enter();
 
-                if (Long.SIZE - Long.numberOfLeadingZeros(a) + b > Long.SIZE - 1) {
+                if (canShiftIntoLong(a, b)) {
+                    return a << b;
+                } else {
                     useBignumProfile.enter();
                     return fixnumOrBignum.fixnumOrBignum(SlowPathBigInteger.shiftLeft(BigInteger.valueOf(a), b));
-                } else {
-                    return a << b;
                 }
             } else {
                 bNotAboveZeroProfile.enter();
@@ -1214,6 +1242,14 @@ public Object leftShift(long a, int b) {
             }
         }
 
+        static boolean canShiftIntoInt(int a, int b) {
+            return Integer.numberOfLeadingZeros(a) - b > 0;
+        }
+
+        static boolean canShiftIntoLong(long a, int b) {
+            return Long.numberOfLeadingZeros(a) - b > 0;
+        }
+
     }
 
     @CoreMethod(names = ">>", required = 1, lowerFixnumParameters = 0)