Merge pull request github#4730 from MathiasVP/definitionHasPhiNode-join-order-fix

C++: Fix join order in definitionHasPhiNode

Author: jbj

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/SSAConstruction.qll

@@ -404,17 +404,28 @@ private import PhiInsertion
  */
 private module PhiInsertion {
   /**
-   * Holds if a `Phi` instruction needs to be inserted for ___location `defLocation` at the beginning of block `phiBlock`.
+   * Holds if `phiBlock` is a block in the dominance frontier of a block that has a definition of the
+   * memory ___location `defLocation`.
    */
-  predicate definitionHasPhiNode(Alias::MemoryLocation defLocation, OldBlock phiBlock) {
+  pragma[noinline]
+  private predicate dominanceFrontierOfDefinition(
+    Alias::MemoryLocation defLocation, OldBlock phiBlock
+  ) {
     exists(OldBlock defBlock |
       phiBlock = Dominance::getDominanceFrontier(defBlock) and
-      definitionHasDefinitionInBlock(defLocation, defBlock) and
-      /* We can also eliminate those nodes where the definition is not live on any incoming edge */
-      definitionLiveOnEntryToBlock(defLocation, phiBlock)
+      definitionHasDefinitionInBlock(defLocation, defBlock)
     )
   }
 
+  /**
+   * Holds if a `Phi` instruction needs to be inserted for ___location `defLocation` at the beginning of block `phiBlock`.
+   */
+  predicate definitionHasPhiNode(Alias::MemoryLocation defLocation, OldBlock phiBlock) {
+    dominanceFrontierOfDefinition(defLocation, phiBlock) and
+    /* We can also eliminate those nodes where the definition is not live on any incoming edge */
+    definitionLiveOnEntryToBlock(defLocation, phiBlock)
+  }
+
   /**
    * Holds if the memory ___location `defLocation` has a definition in block `block`, either because of an existing
    * instruction, a `Phi` node, or a `Chi` node.

cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/SSAConstruction.qll

@@ -404,17 +404,28 @@ private import PhiInsertion
  */
 private module PhiInsertion {
   /**
-   * Holds if a `Phi` instruction needs to be inserted for ___location `defLocation` at the beginning of block `phiBlock`.
+   * Holds if `phiBlock` is a block in the dominance frontier of a block that has a definition of the
+   * memory ___location `defLocation`.
    */
-  predicate definitionHasPhiNode(Alias::MemoryLocation defLocation, OldBlock phiBlock) {
+  pragma[noinline]
+  private predicate dominanceFrontierOfDefinition(
+    Alias::MemoryLocation defLocation, OldBlock phiBlock
+  ) {
     exists(OldBlock defBlock |
       phiBlock = Dominance::getDominanceFrontier(defBlock) and
-      definitionHasDefinitionInBlock(defLocation, defBlock) and
-      /* We can also eliminate those nodes where the definition is not live on any incoming edge */
-      definitionLiveOnEntryToBlock(defLocation, phiBlock)
+      definitionHasDefinitionInBlock(defLocation, defBlock)
     )
   }
 
+  /**
+   * Holds if a `Phi` instruction needs to be inserted for ___location `defLocation` at the beginning of block `phiBlock`.
+   */
+  predicate definitionHasPhiNode(Alias::MemoryLocation defLocation, OldBlock phiBlock) {
+    dominanceFrontierOfDefinition(defLocation, phiBlock) and
+    /* We can also eliminate those nodes where the definition is not live on any incoming edge */
+    definitionLiveOnEntryToBlock(defLocation, phiBlock)
+  }
+
   /**
    * Holds if the memory ___location `defLocation` has a definition in block `block`, either because of an existing
    * instruction, a `Phi` node, or a `Chi` node.

csharp/ql/src/experimental/ir/implementation/unaliased_ssa/internal/SSAConstruction.qll

@@ -404,17 +404,28 @@ private import PhiInsertion
  */
 private module PhiInsertion {
   /**
-   * Holds if a `Phi` instruction needs to be inserted for ___location `defLocation` at the beginning of block `phiBlock`.
+   * Holds if `phiBlock` is a block in the dominance frontier of a block that has a definition of the
+   * memory ___location `defLocation`.
    */
-  predicate definitionHasPhiNode(Alias::MemoryLocation defLocation, OldBlock phiBlock) {
+  pragma[noinline]
+  private predicate dominanceFrontierOfDefinition(
+    Alias::MemoryLocation defLocation, OldBlock phiBlock
+  ) {
     exists(OldBlock defBlock |
       phiBlock = Dominance::getDominanceFrontier(defBlock) and
-      definitionHasDefinitionInBlock(defLocation, defBlock) and
-      /* We can also eliminate those nodes where the definition is not live on any incoming edge */
-      definitionLiveOnEntryToBlock(defLocation, phiBlock)
+      definitionHasDefinitionInBlock(defLocation, defBlock)
     )
   }
 
+  /**
+   * Holds if a `Phi` instruction needs to be inserted for ___location `defLocation` at the beginning of block `phiBlock`.
+   */
+  predicate definitionHasPhiNode(Alias::MemoryLocation defLocation, OldBlock phiBlock) {
+    dominanceFrontierOfDefinition(defLocation, phiBlock) and
+    /* We can also eliminate those nodes where the definition is not live on any incoming edge */
+    definitionLiveOnEntryToBlock(defLocation, phiBlock)
+  }
+
   /**
    * Holds if the memory ___location `defLocation` has a definition in block `block`, either because of an existing
    * instruction, a `Phi` node, or a `Chi` node.