Merge pull request #1549 from hvitved/csharp/cfg/loop-unrolling

C#: Loop unrolling for `foreach` statements

Author: calumgrant

change-notes/1.23/analysis-csharp.md

@@ -36,5 +36,6 @@ The following changes in version 1.23 affect C# analysis in all applications.
   picture of the partial flow paths from a given source. The feature is
   disabled by default and can be enabled for individual configurations by
   overriding `int explorationLimit()`.
+* `foreach` statements where the body is guaranteed to be executed at least once, such as `foreach (var x in new string[]{ "a", "b", "c" }) { ... }`, are now recognized by all analyses based on the control flow graph (such as SSA, data flow and taint tracking).
 
 ## Changes to autobuilder

csharp/ql/src/semmle/code/csharp/Assignable.qll

@@ -567,6 +567,7 @@ module AssignableDefinitions {
    * entry point of `p`'s callable to basic block `bb` without passing through
    * any assignments to `p`.
    */
+  pragma[nomagic]
   private predicate parameterReachesWithoutDef(Parameter p, ControlFlow::BasicBlock bb) {
     forall(AssignableDefinition def | basicBlockRefParamDef(bb, p, def) |
       isUncertainRefCall(def.getTargetAccess())

csharp/ql/src/semmle/code/csharp/Implements.qll

@@ -65,6 +65,7 @@ predicate implements(Virtualizable m1, Virtualizable m2, ValueOrRefType t) {
  * `I.M()` is compatible with `A.M()` for types `A` and `B`, but not
  * for type `C`, because `C.M()` conflicts.
  */
+pragma[nomagic]
 private Virtualizable getAnImplementedInterfaceMemberForSubType(Virtualizable m, ValueOrRefType t) {
   result = getACompatibleInterfaceMember(m) and
   t = m.getDeclaringType()
@@ -86,6 +87,7 @@ private predicate hasMemberCompatibleWithInterfaceMember(ValueOrRefType t, Virtu
  * signature, and where `m` can potentially be accessed when
  * the interface member is accessed.
  */
+pragma[nomagic]
 private Virtualizable getACompatibleInterfaceMember(Virtualizable m) {
   result = getACompatibleInterfaceMemberAux(m) and
   (
@@ -97,12 +99,14 @@ private Virtualizable getACompatibleInterfaceMember(Virtualizable m) {
   )
 }
 
+pragma[nomagic]
 private Virtualizable getACompatibleExplicitInterfaceMember(Virtualizable m, ValueOrRefType declType) {
   result = getACompatibleInterfaceMemberAux(m) and
   declType = m.getDeclaringType() and
   m.implementsExplicitInterface()
 }
 
+pragma[nomagic]
 private Virtualizable getACompatibleInterfaceMemberAux(Virtualizable m) {
   result = getACompatibleInterfaceAccessor(m) or
   result = getACompatibleInterfaceIndexer(m) or

csharp/ql/src/semmle/code/csharp/controlflow/ControlFlowElement.qll

@@ -32,19 +32,19 @@ class ControlFlowElement extends ExprOrStmtParent, @control_flow_element {
    * several `ControlFlow::Node`s, for example to represent the continuation
    * flow in a `try/catch/finally` construction.
    */
-  Node getAControlFlowNode() { result.getElement() = this }
+  Nodes::ElementNode getAControlFlowNode() { result.getElement() = this }
 
   /**
    * Gets a first control flow node executed within this element.
    */
-  Node getAControlFlowEntryNode() {
+  Nodes::ElementNode getAControlFlowEntryNode() {
     result = Internal::getAControlFlowEntryNode(this).getAControlFlowNode()
   }
 
   /**
    * Gets a potential last control flow node executed within this element.
    */
-  Node getAControlFlowExitNode() {
+  Nodes::ElementNode getAControlFlowExitNode() {
     result = Internal::getAControlFlowExitNode(this).getAControlFlowNode()
   }
 

csharp/ql/src/semmle/code/csharp/controlflow/ControlFlowGraph.qll

@@ -317,6 +317,8 @@ module ControlFlow {
     class ExceptionHandlerSplit = ExceptionHandlerSplitting::ExceptionHandlerSplitImpl;
 
     class BooleanSplit = BooleanSplitting::BooleanSplitImpl;
+
+    class LoopUnrollingSplit = LoopUnrollingSplitting::LoopUnrollingSplitImpl;
   }
 
   class BasicBlock = BBs::BasicBlock;