DataFlow/C++: Get rid of the dataflow hook to modify the 'join' and '…

…branch' metrics in dataflow. These should no longer be needed now that we have second-level scopes.

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DataFlowImplSpecific.qll

@@ -20,8 +20,6 @@ module CppDataFlow implements InputSig<Location> {
 
  Node exprNode(DataFlowExpr e) { result = Public::exprNode(e) }
 
- predicate getAdditionalFlowIntoCallNodeTerm = Private::getAdditionalFlowIntoCallNodeTerm/2;
-
  predicate getSecondLevelScope = Private::getSecondLevelScope/1;
 
  predicate validParameterAliasStep = Private::validParameterAliasStep/2;

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll

@@ -36,28 +36,6 @@ private module Cached {
  not Ssa::ignoreOperand(op) and exists(Ssa::getIRRepresentationOfOperand(op))
  }
  }
-
- /**
- * Gets an additional term that is added to the `join` and `branch` computations to reflect
- * an additional forward or backwards branching factor that is not taken into account
- * when calculating the (virtual) dispatch cost.
- *
- * Argument `arg` is part of a path from a source to a sink, and `p` is the target parameter.
- */
- pragma[nomagic]
- cached
- int getAdditionalFlowIntoCallNodeTerm(ArgumentNode arg, ParameterNode p) {
- DataFlowImplCommon::forceCachingInSameStage() and
- exists(
- ParameterNode switchee, SwitchInstruction switch, ConditionOperand op, DataFlowCall call
- |
- DataFlowImplCommon::viableParamArg(call, p, arg) and
- DataFlowImplCommon::viableParamArg(call, switchee, _) and
- switch.getExpressionOperand() = op and
- getAdditionalFlowIntoCallNodeTermStep+(switchee, operandNode(op)) and
- result = countNumberOfBranchesUsingParameter(switch, p)
- )
- }
 }
 
 import Cached
@@ -1433,78 +1411,6 @@ private predicate localStepsToSwitch(Node node) {
  )
 }
 
-/**
- * Holds if `node` is part of a path from a `ParameterNode` to an operand
- * of a `SwitchInstruction`.
- */
-private predicate localStepsFromParameterToSwitch(Node node) {
- localStepsToSwitch(node) and
- (
- node instanceof ParameterNode
- or
- exists(Node prev |
- localStepsFromParameterToSwitch(prev) and
- localFlowStepWithSummaries(prev, node)
- )
- )
-}
-
-/**
- * The local flow relation `localFlowStepWithSummaries` pruned to only
- * include steps that are part of a path from a `ParameterNode` to an
- * operand of a `SwitchInstruction`.
- */
-private predicate getAdditionalFlowIntoCallNodeTermStep(Node node1, Node node2) {
- localStepsFromParameterToSwitch(node1) and
- localStepsFromParameterToSwitch(node2) and
- localFlowStepWithSummaries(node1, node2)
-}
-
-/** Gets the `IRVariable` associated with the parameter node `p`. */
-pragma[nomagic]
-private IRVariable getIRVariableForParameterNode(ParameterNode p) {
- result = p.(InstructionDirectParameterNode).getIRVariable()
- or
- result.getAst() = p.(IndirectParameterNode).getParameter()
-}
-
-/** Holds if `v` is the source variable corresponding to the parameter represented by `p`. */
-pragma[nomagic]
-private predicate parameterNodeHasSourceVariable(ParameterNode p, Ssa::SourceVariable v) {
- v.getIRVariable() = getIRVariableForParameterNode(p) and
- exists(Position pos | p.isParameterOf(_, pos) |
- pos instanceof DirectPosition and
- v.getIndirection() = 1
- or
- pos.(IndirectionPosition).getIndirectionIndex() + 1 = v.getIndirection()
- )
-}
-
-private EdgeKind caseOrDefaultEdge() {
- result instanceof CaseEdge or
- result instanceof DefaultEdge
-}
-
-/**
- * Gets the number of switch branches that that read from (or write to) the parameter `p`.
- */
-private int countNumberOfBranchesUsingParameter(SwitchInstruction switch, ParameterNode p) {
- exists(Ssa::SourceVariable sv |
- parameterNodeHasSourceVariable(p, sv) and
- // Count the number of cases that use the parameter. We do this by finding the phi node
- // that merges the uses/defs of the parameter. There might be multiple such phi nodes, so
- // we pick the one with the highest edge count.
- result =
- max(SsaPhiNode phi |
- switch.getSuccessor(caseOrDefaultEdge()).getBlock().dominanceFrontier() =
- phi.getBasicBlock() and
- phi.getSourceVariable() = sv
- |
- strictcount(phi.getAnInput())
- )
- )
-}
-
 pragma[nomagic]
 private predicate isInputOutput(
  DF::DataFlowFunction target, Node node1, Node node2, IO::FunctionInput input,

shared/dataflow/codeql/dataflow/DataFlow.qll

@@ -299,15 +299,6 @@ signature module InputSig<LocationSig Location> {
  */
  default predicate neverSkipInPathGraph(Node n) { none() }
 
- /**
- * Gets an additional term that is added to the `join` and `branch` computations to reflect
- * an additional forward or backwards branching factor that is not taken into account
- * when calculating the (virtual) dispatch cost.
- *
- * Argument `arg` is part of a path from a source to a sink, and `p` is the target parameter.
- */
- default int getAdditionalFlowIntoCallNodeTerm(ArgumentNode arg, ParameterNode p) { none() }
-
  /**
  * A second-level control-flow scope in a callable.
  *

shared/dataflow/codeql/dataflow/internal/DataFlowImpl.qll

@@ -1102,17 +1102,6 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
  not inBarrier(p)
  }
 
- /**
- * Gets an additional term that is added to `branch` and `join` when deciding whether
- * the amount of forward or backward branching is within the limit specified by the
- * configuration.
- */
- pragma[nomagic]
- private int getLanguageSpecificFlowIntoCallNodeCand1(ArgNodeEx arg, ParamNodeEx p) {
- flowIntoCallNodeCand1(_, arg, p) and
- result = getAdditionalFlowIntoCallNodeTerm(arg.projectToNode(), p.projectToNode())
- }
-
  private module SndLevelScopeOption = Option<DataFlowSecondLevelScope>;
 
  private class SndLevelScopeOption = SndLevelScopeOption::Option;
@@ -1177,11 +1166,11 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
  private int branch(ArgNodeEx n1) {
  result =
  strictcount(DataFlowCallable c |
-  exists(NodeEx n |
-  flowIntoCallNodeCand1(_, n1, n) and
-  c = n.getEnclosingCallable()
-  )
-  ) + sum(ParamNodeEx p1 | | getLanguageSpecificFlowIntoCallNodeCand1(n1, p1))
+ exists(NodeEx n |
+ flowIntoCallNodeCand1(_, n1, n) and
+ c = n.getEnclosingCallable()
+ )
+ )
  }
 
  /**
@@ -1193,11 +1182,11 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
  private int join(ParamNodeEx n2) {
  result =
  strictcount(DataFlowCallable c |
-  exists(NodeEx n |
-  flowIntoCallNodeCand1(_, n, n2) and
-  c = n.getEnclosingCallable()
-  )
-  ) + sum(ArgNodeEx arg2 | | getLanguageSpecificFlowIntoCallNodeCand1(arg2, n2))
+ exists(NodeEx n |
+ flowIntoCallNodeCand1(_, n, n2) and
+ c = n.getEnclosingCallable()
+ )
+ )
  }
 
  /**