Brodes/seh flow phase2 splitting seh edges

cpp/ql/lib/semmle/code/cpp/ir/implementation/EdgeKind.qll

@@ -3,13 +3,13 @@
  */
 
 private import internal.EdgeKindInternal
-private import codeql.util.Boolean
 
 private newtype TEdgeKind =
   TGotoEdge() or // Single successor (including fall-through)
   TTrueEdge() or // 'true' edge of conditional branch
   TFalseEdge() or // 'false' edge of conditional branch
-  TExceptionEdge(Boolean isSeh) or // Thrown exception, true for SEH exceptions, false otherwise
+  TCppExceptionEdge() or // Thrown C++ exception
+  TSehExceptionEdge() or // Thrown C++ exception
   TDefaultEdge() or // 'default' label of switch
   TCaseEdge(string minValue, string maxValue) {
     // Case label of switch
@@ -52,23 +52,33 @@ class FalseEdge extends EdgeKindImpl, TFalseEdge {
   final override string toString() { result = "False" }
 }
 
+abstract private class ExceptionEdgeImpl extends EdgeKindImpl { }
+
 /**
  * An "exception" edge, representing the successor of an instruction when that
  * instruction's evaluation throws an exception.
+ *
+ * Exception edges are expclitly sublcassed to
+ * `CppExceptionEdge` and `SehExceptionEdge` only.
+ * Further sublcasses, if required, should be added privately
+ * here for IR efficiency.
  */
-class ExceptionEdge extends EdgeKind, TExceptionEdge {
-  Boolean isSeh; //true for Structured Exception Handling, false for C++ exceptions
-
-  ExceptionEdge() { this = TExceptionEdge(isSeh) }
+final class ExceptionEdge = ExceptionEdgeImpl;
 
-  /**
-   * Holds if the exception is a Structured Exception Handling (SEH) exception.
-   */
-  final predicate isSeh() { isSeh = true }
+/**
+ * An "exception" edge, representing the successor of an instruction when that
+ * instruction's evaluation throws an exception for C++ exceptions
+ */
+class CppExceptionEdge extends ExceptionEdgeImpl, TCppExceptionEdge {
+  final override string toString() { result = "C++ Exception" }
+}
 
-  final override string toString() {
-    if isSeh = true then result = "SEH Exception" else result = "C++ Exception"
-  }
+/**
+ * An "exception" edge, representing the successor of an instruction when that
+ * instruction's evaluation throws an exception for SEH exceptions
+ */
+class SehExceptionEdge extends ExceptionEdgeImpl, TSehExceptionEdge {
+  final override string toString() { result = "SEH Exception" }
 }
 
 /**
@@ -135,11 +145,22 @@ module EdgeKind {
   FalseEdge falseEdge() { result = TFalseEdge() }
 
   /**
-   * Gets the single instance of the `ExceptionEdge` class.
-   * Gets the instance of the `ExceptionEdge` class.
-   * `isSeh` is true if the exception is an SEH exception, and false for a C++ edge.
+   * Gets an instance of the `CppExceptionEdge` class.
+   */
+  CppExceptionEdge cppExceptionEdge() { result = TCppExceptionEdge() }
+
+  /**
+   * Gets an instance of the `SehExceptionEdge` class.
    */
-  ExceptionEdge exceptionEdge(Boolean isSeh) { result = TExceptionEdge(isSeh) }
+  SehExceptionEdge sehExceptionEdge() { result = TSehExceptionEdge() }
+
+  /**
+   * Gets an instance of the `ExceptionEdge` class.
+   */
+  ExceptionEdge exceptionEdge() {
+    result = cppExceptionEdge() or
+    result = sehExceptionEdge()
+  }
 
   /**
    * Gets the single instance of the `DefaultEdge` class.

cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/TranslatedCall.qll

@@ -88,7 +88,7 @@ abstract class TranslatedCall extends TranslatedExpr {
       result = this.getParent().getChildSuccessor(this, kind)
       or
       this.mayThrowException() and
-      kind = EdgeKind::exceptionEdge(false) and
+      kind instanceof CppExceptionEdge and
       result = this.getParent().getExceptionSuccessorInstruction(any(GotoEdge edge))
     )
   }

cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/TranslatedExpr.qll

@@ -3039,7 +3039,7 @@ class TranslatedDestructorsAfterThrow extends TranslatedElement, TTranslatedDest
       or
       // And otherwise, exit this element with an exceptional edge
       not exists(this.getChild(id + 1)) and
-      kind = EdgeKind::exceptionEdge(false) and
+      kind instanceof CppExceptionEdge and
       result = this.getParent().getExceptionSuccessorInstruction(any(GotoEdge edge))
     )
   }
@@ -3078,7 +3078,7 @@ abstract class TranslatedThrowExpr extends TranslatedNonConstantExpr {
       result = this.getDestructors().getFirstInstruction(kind)
       or
       not exists(this.getDestructors()) and
-      kind = EdgeKind::exceptionEdge(false) and
+      kind instanceof CppExceptionEdge and
       result = this.getParent().getExceptionSuccessorInstruction(any(GotoEdge edge))
     )
   }

cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/TranslatedStmt.qll

@@ -932,7 +932,7 @@ class TranslatedCatchByTypeHandler extends TranslatedHandler {
       kind instanceof GotoEdge and
       result = this.getParameter().getFirstInstruction(kind)
       or
-      kind = EdgeKind::exceptionEdge(false) and
+      kind instanceof CppExceptionEdge and
       if exists(this.getDestructors())
       then result = this.getDestructors().getFirstInstruction(any(GotoEdge edge))
       else result = this.getParent().(TranslatedTryStmt).getNextHandler(this, any(GotoEdge edge))