C++: Use or instead of if

The proposition in the true branch implied the condition, so `or` is more appropriate. Also eliminated an existentially quantified variable.

cpp/ql/lib/semmle/code/cpp/rangeanalysis/SimpleRangeAnalysis.qll

@@ -111,25 +111,24 @@ float widenUpperBound(Type type, float ub) {
  * compilation units, which doesn't necessarily have a getValue() result from the extractor.
  */
 private string getValue(Expr e) {
-  if exists(e.getValue())
+  result = e.getValue()
-  then result = e.getValue()
+  or
-  else
+  not exists(e.getValue()) and
-    /*
+  /*
-     * It should be safe to propagate the initialization value to a variable if:
+   * It should be safe to propagate the initialization value to a variable if:
-     * The type of v is const, and
+   * The type of v is const, and
-     * The type of v is not volatile, and
+   * The type of v is not volatile, and
-     * Either:
+   * Either:
-     *   v is a local/global variable, or
+   *   v is a local/global variable, or
-     *   v is a static member variable
+   *   v is a static member variable
-     */
+   */
 
-    exists(VariableAccess access, StaticStorageDurationVariable v |
+  exists(StaticStorageDurationVariable v |
-      not v.getUnderlyingType().isVolatile() and
+    not v.getUnderlyingType().isVolatile() and
-      v.getUnderlyingType().isConst() and
+    v.getUnderlyingType().isConst() and
-      e = access and
+    v = e.(VariableAccess).getTarget() and
-      v = access.getTarget() and
+    result = getValue(v.getAnAssignedValue())
-      result = getValue(v.getAnAssignedValue())
+  )
-    )
 }
 
 /**