[6.0][Caching] Add fast swift instance setup for cache replay

include/swift/Frontend/Frontend.h

@@ -691,6 +691,10 @@ class CompilerInstance {
  bool setup(const CompilerInvocation &Invocation, std::string &Error,
  ArrayRef<const char *> Args = {});
 
+ /// The fast setup function for cache replay.
+ bool setupForReplay(const CompilerInvocation &Invocation, std::string &Error,
+ ArrayRef<const char *> Args = {});
+
  const CompilerInvocation &getInvocation() const { return Invocation; }
 
  /// If a IDE inspection buffer has been set, returns the corresponding source

lib/Frontend/Frontend.cpp

@@ -562,6 +562,23 @@ bool CompilerInstance::setup(const CompilerInvocation &Invoke,
  return false;
 }
 
+bool CompilerInstance::setupForReplay(const CompilerInvocation &Invoke,
+ std::string &Error,
+ ArrayRef<const char *> Args) {
+ // This is the fast path for setup an instance for replay but cannot run
+ // regular compilation.
+ Invocation = Invoke;
+
+ if (setupCASIfNeeded(Args)) {
+ Error = "Setting up CAS failed";
+ return true;
+ }
+
+ setupOutputBackend();
+ setupCachingDiagnosticsProcessorIfNeeded();
+ return false;
+}
+
 bool CompilerInstance::setUpVirtualFileSystemOverlays() {
  if (Invocation.getCASOptions().requireCASFS()) {
  const auto &Opts = getInvocation().getCASOptions();

tools/libSwiftScan/SwiftCaching.cpp

@@ -932,7 +932,8 @@ static llvm::Error replayCompilation(SwiftScanReplayInstance &Instance,
  Invocation.getDiagnosticOptions().EmitMacroExpansionFiles);
 
  std::string InstanceSetupError;
- if (Inst.setup(Instance.Invocation, InstanceSetupError, Instance.Args))
+ if (Inst.setupForReplay(Instance.Invocation, InstanceSetupError,
+ Instance.Args))
  return createStringError(inconvertibleErrorCode(), InstanceSetupError);
 
  auto *CDP = Inst.getCachingDiagnosticsProcessor();