Support to keep bounds derived on implicit integer casts.

Author: criemen

cpp/ql/src/semmle/code/cpp/rangeanalysis/RangeAnalysis.qll

@@ -187,6 +187,13 @@ private predicate boundFlowStepSsa(
     guard.controls(op2.getUse().getBlock(), testIsTrue) and
     reason = TCondReason(guard)
   )
+  or
+  exists(IRGuardCondition guard, boolean testIsTrue, SafeCastInstruction cast |
+    valueNumberOfOperand(op2) = valueNumber(cast.getUnary()) and
+    guard = boundFlowCond(valueNumber(cast), op1, delta, upper, testIsTrue) and
+    guard.controls(op2.getUse().getBlock(), testIsTrue) and
+    reason = TCondReason(guard)
+  )
 }
 
 /**

cpp/ql/test/library-tests/rangeanalysis/rangeanalysis/test.cpp

@@ -192,3 +192,19 @@ int test16(int i) {
   long l;
   l = i;
 }
+
+// implicit integer casts
+void test17(int i, long l) {
+  if (i < l) {
+    sink(i);
+  }
+  if (i < l - 2) {
+    sink (i);
+  }
+}
+
+void test18(int x, int y) {
+  if (x < y - 2) {
+    sink(x);
+  }
+}