# HG changeset patch
# User Lukas Stadler <lukas.stadler@oracle.com>
# Date 1404993892 -7200
# Node ID 41906973537e07fc4b894fd830c961796110b86a
# Parent  394b949fec5afb8f3a49d54a2df25ad6a3977b49
better stamps for left shifts with fixed shift amount

diff -r 394b949fec5a -r 41906973537e graal/com.oracle.graal.nodes.test/src/com/oracle/graal/nodes/test/IntegerStampTest.java
--- a/graal/com.oracle.graal.nodes.test/src/com/oracle/graal/nodes/test/IntegerStampTest.java	Thu Jul 10 14:04:16 2014 +0200
+++ b/graal/com.oracle.graal.nodes.test/src/com/oracle/graal/nodes/test/IntegerStampTest.java	Thu Jul 10 14:04:52 2014 +0200
@@ -299,4 +299,16 @@
         assertFalse(new IntegerStamp(32, 0, 0xff00, 0, 0xff00).join(new IntegerStamp(32, 1, 0xff, 0x00, 0xff)).isLegal());
         assertFalse(new IntegerStamp(32, 0x100, 0xff00, 0, 0xff00).join(new IntegerStamp(32, 0, 0xff, 0x00, 0xff)).isLegal());
     }
+
+    @Test
+    public void testShiftLeft() {
+        assertEquals(new IntegerStamp(32, 0, 0x1ff, 0, 0x1ff), StampTool.leftShift(new IntegerStamp(32, 0, 0xff, 0, 0xff), new IntegerStamp(32, 0, 1, 0, 1)));
+        assertEquals(new IntegerStamp(32, 0, 0x1fe0, 0, 0x1fe0), StampTool.leftShift(new IntegerStamp(32, 0, 0xff, 0, 0xff), new IntegerStamp(32, 5, 5, 5, 5)));
+        assertEquals(new IntegerStamp(32, 0x1e0, 0x1fe0, 0, 0x1fe0), StampTool.leftShift(new IntegerStamp(32, 0xf, 0xff, 0, 0xff), new IntegerStamp(32, 5, 5, 5, 5)));
+
+        assertEquals(new IntegerStamp(64, 0, 0x1ff, 0, 0x1ff), StampTool.leftShift(new IntegerStamp(64, 0, 0xff, 0, 0xff), new IntegerStamp(32, 0, 1, 0, 1)));
+        assertEquals(new IntegerStamp(64, 0, 0x1fe0, 0, 0x1fe0), StampTool.leftShift(new IntegerStamp(64, 0, 0xff, 0, 0xff), new IntegerStamp(32, 5, 5, 5, 5)));
+        assertEquals(new IntegerStamp(64, 0x1e0, 0x1fe0, 0, 0x1fe0), StampTool.leftShift(new IntegerStamp(64, 0xf, 0xff, 0, 0xff), new IntegerStamp(32, 5, 5, 5, 5)));
+
+    }
 }
diff -r 394b949fec5a -r 41906973537e graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/type/StampTool.java
--- a/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/type/StampTool.java	Thu Jul 10 14:04:16 2014 +0200
+++ b/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/type/StampTool.java	Thu Jul 10 14:04:52 2014 +0200
@@ -298,6 +298,18 @@
         }
         int shiftBits = bits > 32 ? 6 : 5;
         long shiftMask = bits > 32 ? 0x3FL : 0x1FL;
+        if (shift.lowerBound() == shift.upperBound()) {
+            int shiftAmount = (int) (shift.lowerBound() & shiftMask);
+            if (shiftAmount == 0) {
+                return value;
+            }
+            // the mask of bits that will be lost or shifted into the sign bit
+            long removedBits = -1L << (bits - shiftAmount - 1);
+            if ((value.lowerBound() & removedBits) == 0 && (value.upperBound() & removedBits) == 0) {
+                // use a better stamp if neither lower nor upper bound can lose bits
+                return new IntegerStamp(bits, value.lowerBound() << shiftAmount, value.upperBound() << shiftAmount, value.downMask() << shiftAmount, value.upMask() << shiftAmount);
+            }
+        }
         if ((shift.lowerBound() >>> shiftBits) == (shift.upperBound() >>> shiftBits)) {
             long downMask = defaultMask;
             long upMask = 0;