Merge pull request #17326 from rudkx/add-option-to-disable-shrink

Add a frontend option to disable the "shrink" part of the solver.

Author: rudkx

include/swift/Basic/LangOptions.h

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -183,6 +183,9 @@ namespace swift {
     /// before termination of the shrink phrase of the constraint solver.
     unsigned SolverShrinkUnsolvedThreshold = 10;
 
+    /// Disable the shrink phase of the expression type checker.
+    bool SolverDisableShrink = false;
+
     /// The maximum depth to which to test decl circularity.
     unsigned MaxCircularityDepth = 500;
 

include/swift/Option/FrontendOptions.td

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -345,6 +345,10 @@ def warn_long_expression_type_checking_EQ : Joined<["-"], "warn-long-expression-
 
 def solver_expression_time_threshold_EQ : Joined<["-"], "solver-expression-time-threshold=">;
 
+def solver_disable_shrink :
+  Flag<["-"], "solver-disable-shrink">,
+  HelpText<"Disable the shrink phase of expression type checking">;
+
 def switch_checking_invocation_threshold_EQ : Joined<["-"],
     "switch-checking-invocation-threshold=">;
 

lib/Frontend/CompilerInvocation.cpp

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -279,6 +279,9 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
     Opts.SolverShrinkUnsolvedThreshold = threshold;
   }
 
+  if (const Arg *A = Args.getLastArg(OPT_solver_disable_shrink))
+    Opts.SolverDisableShrink = true;
+
   if (const Arg *A = Args.getLastArg(OPT_value_recursion_threshold)) {
     unsigned threshold;
     if (StringRef(A->getValue()).getAsInteger(10, threshold)) {

lib/Sema/CSSolver.cpp

@@ -981,6 +981,9 @@ void ConstraintSystem::Candidate::applySolutions(
 }
 
 void ConstraintSystem::shrink(Expr *expr) {
+  if (TC.getLangOpts().SolverDisableShrink)
+    return;
+
   using DomainMap = llvm::SmallDenseMap<Expr *, ArrayRef<ValueDecl *>>;
 
   // A collection of original domains of all of the expressions,