[clang] Unconditionally add autolink hints for frameworks.

[ributzka]

Summary

Clang infers framework autolink hints when parsing a modulemap. In order to do
so, it checks if the module is a framework and if there is a framework binary
or TBD file in the SDK. Only when Clang finds the filei, then the autolink hint
is added to the module metadata.

During a project build many clang processes perform this check, which causes
many stat calls - even for modules/frameworks that are not even used.

The linker is already resilient to non-existing framework links that come from
the autolink metadata, so there is no need for Clang to do this check.

Instead the autolink hints are now added unconditionally and the linker only
needs to do the check once. This reduces the overall number of stat calls.

This fixes rdar://106578342.

[pete]

LGTM

[Bigcheese]

lgtm

[ributzka]

Thanks for the prompt reviews

clang/lib/Lex/ModuleMap.cpp

Module *ModuleMap::createHeaderUnit(SourceLocation Loc, StringRef Name,
   Result->Kind = Module::ModuleHeaderUnit;
   Modules[Name] = SourceModule = Result;
   addHeader(Result, H, NormalHeader);
   return Result;
 }
 
 /// For a framework module, infer the framework against which we
 /// should link.
-static void inferFrameworkLink(Module *Mod, const DirectoryEntry *FrameworkDir,
-                               FileManager &FileMgr) {
+static void inferFrameworkLink(Module *Mod) {
   assert(Mod->IsFramework && "Can only infer linking for framework modules");
   assert(!Mod->isSubFramework() &&
          "Can only infer linking for top-level frameworks");
 
-  SmallString<128> LibName;
-  LibName += FrameworkDir->getName();
-  llvm::sys::path::append(LibName, Mod->Name);
-
-  // The library name of a framework has more than one possible extension since
-  // the introduction of the text-based dynamic library format. We need to check
-  // for both before we give up.
-  for (const char *extension : {"", ".tbd"}) {
-    llvm::sys::path::replace_extension(LibName, extension);
-    if (FileMgr.getFile(LibName)) {
-      Mod->LinkLibraries.push_back(Module::LinkLibrary(Mod->Name,
-                                                       /*IsFramework=*/true));
-      return;
-    }
-  }
 }
 
 Module *ModuleMap::inferFrameworkModule(const DirectoryEntry *FrameworkDir,
                                         bool IsSystem, Module *Parent) {
   Attributes Attrs;
   Attrs.IsSystem = IsSystem;
   return inferFrameworkModule(FrameworkDir, Attrs, Parent);
 }
if (auto SubframeworkDir =
 
       // FIXME: Do we want to warn about subframeworks without umbrella headers?
       inferFrameworkModule(*SubframeworkDir, Attrs, Result);
     }
   }
 
   // If the module is a top-level framework, automatically link against the
   // framework.
-  if (!Result->isSubFramework()) {
-    inferFrameworkLink(Result, FrameworkDir, FileMgr);
-  }
+  if (!Result->isSubFramework())
+    inferFrameworkLink(Result);
 
   return Result;
 }
 
 Module *ModuleMap::createShadowedModule(StringRef Name, bool IsFramework,
                                         Module *ShadowingModule) {
 
   // Create a new module with this name.
else {
     Diags.Report(Tok.getLocation(), diag::err_mmap_expected_rbrace);
     Diags.Report(LBraceLoc, diag::note_mmap_lbrace_match);
     HadError = true;
   }
 
   // If the active module is a top-level framework, and there are no link
   // libraries, automatically link against the framework.
   if (ActiveModule->IsFramework && !ActiveModule->isSubFramework() &&
-      ActiveModule->LinkLibraries.empty()) {
-    inferFrameworkLink(ActiveModule, Directory, SourceMgr.getFileManager());
-  }
+      ActiveModule->LinkLibraries.empty())
+    inferFrameworkLink(ActiveModule);
 
   // If the module meets all requirements but is still unavailable, mark the
   // whole tree as unavailable to prevent it from building.
   if (!ActiveModule->IsAvailable && !ActiveModule->IsUnimportable &&
       ActiveModule->Parent) {
     ActiveModule->getTopLevelModule()->markUnavailable(/*Unimportable=*/false);
     ActiveModule->getTopLevelModule()->MissingHeaders.append(
       ActiveModule->MissingHeaders.begin(), ActiveModule->MissingHeaders.end());

clang/test/Modules/use-exportas-for-link.m

 // RUN: %clang_cc1 -emit-llvm -o - -fmodules-cache-path=%t -DD -fmodules -fimplicit-module-maps -F %S/Inputs/exportas-link %s | FileCheck --check-prefix=CHECK_D %s
 // CHECK_D: !llvm.linker.options = !{![[MODULE:[0-9]+]]}
 // CHECK_D: ![[MODULE]] = !{!"-framework", !"SomeKit"}
 #ifdef D
 @import SomeKit;
 #endif
 
 // RUN: %clang_cc1 -emit-llvm -o - -fmodules-cache-path=%t -DE -fmodules -fimplicit-module-maps -F %S/Inputs/exportas-link %s | FileCheck --check-prefix=CHECK_E %s
-// CHECK_E: !llvm.linker.options = !{![[MODULE:[0-9]+]]}
-// CHECK_E: ![[MODULE]] = !{!"-framework", !"SomeKitCore"}
+// CHECK_E: !llvm.linker.options = !{![[MODULE1:[0-9]+]], ![[MODULE2:[0-9]+]]}
+// CHECK_E: ![[MODULE1]] = !{!"-framework", !"OtherKit"}
+// CHECK_E: ![[MODULE2]] = !{!"-framework", !"SomeKitCore"}
 #ifdef E
 @import OtherKit;
 #endif
 
 // RUN: %clang_cc1 -emit-llvm -o - -fmodules-cache-path=%t -DF -fmodules -fimplicit-module-maps -F %S/Inputs/exportas-link %s | FileCheck --check-prefix=CHECK_F %s
-// CHECK_F: !llvm.linker.options = !{![[MODULE:[0-9]+]]}
-// CHECK_F: ![[MODULE]] = !{!"-framework", !"SomeKit"}
+// CHECK_F: !llvm.linker.options = !{![[MODULE1:[0-9]+]], ![[MODULE2:[0-9]+]]}
+// CHECK_F: ![[MODULE1]] = !{!"-framework", !"OtherKit"}
+// CHECK_F: ![[MODULE2]] = !{!"-framework", !"SomeKit"}
 #ifdef F
 @import OtherKit;
 #endif