Sema: Allow turning off expression timer with -solver-expression-time-threshold=0

Author: slavapestov

include/swift/Sema/ConstraintSystem.h

@@ -250,9 +250,6 @@ class ExpressionTimer {
   bool PrintWarning;
 
 public:
-  /// This constructor sets a default threshold defined for all expressions
-  /// via compiler flag `solver-expression-time-threshold`.
-  ExpressionTimer(AnchorType Anchor, ConstraintSystem &CS);
   ExpressionTimer(AnchorType Anchor, ConstraintSystem &CS,
                   unsigned thresholdInSecs);
 
@@ -5494,7 +5491,9 @@ class ConstraintSystem {
   /// increase the likelihood that a favored constraint will be successfully
   /// resolved before any others.
   void optimizeConstraints(Expr *e);
-  
+
+  void startExpressionTimer(ExpressionTimer::AnchorType anchor);
+
   /// Determine if we've already explored too many paths in an
   /// attempt to solve this expression.
   std::pair<bool, SourceRange> isAlreadyTooComplex = {false, SourceRange()};

lib/Sema/CSSolver.cpp

@@ -822,7 +822,7 @@ bool ConstraintSystem::Candidate::solve(
   ConstraintSystem cs(DC, std::nullopt);
 
   // Set up expression type checker timer for the candidate.
-  cs.Timer.emplace(E, cs);
+  cs.startExpressionTimer(E);
 
   // Generate constraints for the new system.
   if (auto generatedExpr = cs.generateConstraints(E, DC)) {
@@ -1521,7 +1521,7 @@ ConstraintSystem::solveImpl(SyntacticElementTarget &target,
 
   // Set up the expression type checker timer.
   if (Expr *expr = target.getAsExpr())
-    Timer.emplace(expr, *this);
+    startExpressionTimer(expr);
 
   if (generateConstraints(target, allowFreeTypeVariables))
     return SolutionResult::forError();
@@ -1707,7 +1707,7 @@ bool ConstraintSystem::solveForCodeCompletion(
     setContextualInfo(expr, target.getExprContextualTypeInfo());
 
     // Set up the expression type checker timer.
-    Timer.emplace(expr, *this);
+    startExpressionTimer(expr);
 
     shrink(expr);
   }

lib/Sema/CSStep.cpp

@@ -901,7 +901,8 @@ bool ConjunctionStep::attempt(const ConjunctionElement &element) {
   // is important for closures with large number of statements
   // in them.
   if (CS.Timer) {
-    CS.Timer.emplace(element.getLocator(), CS);
+    CS.Timer.reset();
+    CS.startExpressionTimer(element.getLocator());
   }
 
   auto success = element.attempt(CS);

lib/Sema/ConstraintSystem.cpp

@@ -52,11 +52,6 @@ using namespace inference;
 
 #define DEBUG_TYPE "ConstraintSystem"
 
-ExpressionTimer::ExpressionTimer(AnchorType Anchor, ConstraintSystem &CS)
-    : ExpressionTimer(
-          Anchor, CS,
-          CS.getASTContext().TypeCheckerOpts.ExpressionTimeoutThreshold) {}
-
 ExpressionTimer::ExpressionTimer(AnchorType Anchor, ConstraintSystem &CS,
                                  unsigned thresholdInSecs)
     : Anchor(Anchor), Context(CS.getASTContext()),
@@ -139,6 +134,16 @@ ConstraintSystem::~ConstraintSystem() {
   delete &CG;
 }
 
+void ConstraintSystem::startExpressionTimer(ExpressionTimer::AnchorType anchor) {
+  ASSERT(!Timer);
+
+  unsigned timeout = getASTContext().TypeCheckerOpts.ExpressionTimeoutThreshold;
+  if (timeout == 0)
+    return;
+
+  Timer.emplace(anchor, *this, timeout);
+}
+
 void ConstraintSystem::incrementScopeCounter() {
   ++NumSolverScopes;
   if (auto *Stats = getASTContext().Stats)