[vm/compiler] Avoid undefined behavior in range analysis shift operation

Change-Id: I232f86b58c71746ea6ccb479f28d812c29027938
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/127141
Reviewed-by: Vyacheslav Egorov <vegorov@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>

Author: mkustermann

runtime/vm/compiler/backend/range_analysis.cc

@@ -1814,10 +1814,12 @@ RangeBoundary RangeBoundary::Shl(const RangeBoundary& value_boundary,
   int64_t limit = 64 - shift_count;
   int64_t value = value_boundary.ConstantValue();
 
-  if ((value == 0) || (shift_count == 0) ||
-      ((limit > 0) && Utils::IsInt(static_cast<int>(limit), value))) {
+  if (value == 0) {
+    return RangeBoundary(0);
+  } else if (shift_count == 0 ||
+             (limit > 0 && Utils::IsInt(static_cast<int>(limit), value))) {
     // Result stays in 64 bit range.
-    int64_t result = value << shift_count;
+    const int64_t result = value << shift_count;
     return RangeBoundary(result);
   }