compute trip countd with overflow

Author: davleopo

compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/loop/CountedLoopInfo.java

@@ -696,7 +696,7 @@ public boolean ivCanNeverOverflow(InductionVariable iv) {
             if (iv.isConstantInit() && isConstantMaxTripCount() && iv.isConstantStride()) {
                 try {
                     final int bits = IntegerStamp.getBits(iv.valueNode().stamp(NodeView.DEFAULT));
-                    long tripCountMinus1 = LoopUtility.subtractExact(bits, maxTripCountNode().asJavaConstant().asLong(), 1);
+                    long tripCountMinus1 = LoopUtility.subtractExact(bits, LoopUtility.tripCountSignedExact(this), 1);
                     long stripTimesTripCount = LoopUtility.multiplyExact(bits, iv.constantStride(), tripCountMinus1);
                     @SuppressWarnings("unused")
                     long extremum = LoopUtility.addExact(bits, stripTimesTripCount, iv.initNode().asJavaConstant().asLong());

compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/phases/common/util/LoopUtility.java

@@ -53,6 +53,7 @@
 import jdk.graal.compiler.nodes.cfg.HIRBlock;
 import jdk.graal.compiler.nodes.extended.OpaqueValueNode;
 import jdk.graal.compiler.nodes.loop.BasicInductionVariable;
+import jdk.graal.compiler.nodes.loop.CountedLoopInfo;
 import jdk.graal.compiler.nodes.loop.InductionVariable;
 import jdk.graal.compiler.nodes.loop.Loop;
 import jdk.graal.compiler.nodes.loop.LoopsData;
@@ -61,6 +62,15 @@
 
 public class LoopUtility {
 
+    public static long tripCountSignedExact(CountedLoopInfo loop) {
+        ValueNode maxTripCountNode = loop.maxTripCountNode();
+        final long maxTripCountAsSigned = maxTripCountNode.asJavaConstant().asLong();
+        if (maxTripCountAsSigned < 0) {
+            throw new ArithmeticException("Unsigned value " + maxTripCountAsSigned + " overflows signed range");
+        }
+        return maxTripCountAsSigned;
+    }
+
     public static long addExact(int bits, long a, long b) {
         if (bits == 8) {
             byte ba = NumUtil.safeToByteAE(a);