RequirementMachine: Add a couple of simple counters

Author: slavapestov

include/swift/AST/RewriteSystem.h

@@ -18,6 +18,7 @@
 #include "swift/AST/LayoutConstraint.h"
 #include "swift/AST/ProtocolGraph.h"
 #include "swift/AST/Types.h"
+#include "swift/Basic/Statistic.h"
 #include "llvm/ADT/FoldingSet.h"
 #include "llvm/ADT/PointerUnion.h"
 #include "llvm/ADT/SmallVector.h"
@@ -352,7 +353,10 @@ class RewriteContext final {
   RewriteContext &operator=(RewriteContext &&) = delete;
 
 public:
-  RewriteContext() {}
+  /// Statistical counters.
+  UnifiedStatsReporter *Stats;
+
+  RewriteContext(UnifiedStatsReporter *stats) : Stats(stats) {}
 
   Term getTermForType(CanType paramType,
                       const ProtocolDecl *proto);
@@ -420,6 +424,7 @@ class Rule final {
 ///
 /// Out-of-line methods are documented in RewriteSystem.cpp.
 class RewriteSystem final {
+  /// Rewrite context for memory allocation.
   RewriteContext &Context;
 
   /// The rules added so far, including rules from our client, as well

include/swift/Basic/Statistics.def

@@ -220,6 +220,14 @@ FRONTEND_STATISTIC(Sema, NumAccessorsSynthesized)
 /// Number of synthesized accessor bodies.
 FRONTEND_STATISTIC(Sema, NumAccessorBodiesSynthesized)
 
+/// Number of requirement machines constructed. Rough proxy for
+/// amount of work the requirement machine does analyzing type signatures.
+FRONTEND_STATISTIC(Sema, NumRequirementMachines)
+
+/// Number of requirement machines constructed. Rough proxy for
+/// amount of work the requirement machine does analyzing type signatures.
+FRONTEND_STATISTIC(Sema, NumRequirementMachineCompletionSteps)
+
 /// Number of generic signature builders constructed. Rough proxy for
 /// amount of work the GSB does analyzing type signatures.
 FRONTEND_STATISTIC(Sema, NumGenericSignatureBuilders)

lib/AST/RequirementMachine.cpp

@@ -207,11 +207,12 @@ struct RequirementMachine::Implementation {
   RewriteSystem System;
   bool Complete = false;
 
-  Implementation() : System(Context) {}
+  Implementation(ASTContext &ctx)
+    : Context(ctx.Stats), System(Context) {}
 };
 
 RequirementMachine::RequirementMachine(ASTContext &ctx) : Context(ctx) {
-  Impl = new Implementation();
+  Impl = new Implementation(ctx);
 }
 
 RequirementMachine::~RequirementMachine() {
@@ -223,6 +224,9 @@ void RequirementMachine::addGenericSignature(CanGenericSignature sig) {
 
   auto *Stats = Context.Stats;
 
+  if (Stats)
+    ++Stats->getFrontendCounters().NumRequirementMachines;
+
   FrontendStatsTracer tracer(Stats, "build-rewrite-system");
 
   if (Context.LangOpts.DebugRequirementMachine) {

lib/AST/RewriteSystem.cpp

@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "swift/AST/RewriteSystem.h"
+#include "swift/Basic/Defer.h"
 #include "llvm/ADT/FoldingSet.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
@@ -815,6 +816,15 @@ void RewriteSystem::processMergedAssociatedTypes() {
 RewriteSystem::CompletionResult
 RewriteSystem::computeConfluentCompletion(unsigned maxIterations,
                                           unsigned maxDepth) {
+  unsigned steps = 0;
+
+  SWIFT_DEFER {
+    if (Context.Stats) {
+      Context.Stats->getFrontendCounters()
+        .NumRequirementMachineCompletionSteps += steps;
+    }
+  };
+
   // The worklist must be processed in first-in-first-out order, to ensure
   // that we resolve all overlaps among the initial set of rules before
   // moving on to overlaps between rules introduced by completion.
@@ -881,7 +891,7 @@ RewriteSystem::computeConfluentCompletion(unsigned maxIterations,
       continue;
 
     // Check if we've already done too much work.
-    if (--maxIterations == 0)
+    if (++steps >= maxIterations)
       return CompletionResult::MaxIterations;
 
     const auto &newRule = Rules[i];