[clang] Delay normalization of -fmodules-cache-path

clang/include/clang/Driver/Options.td

@@ -3281,7 +3281,8 @@ defm declspec : BoolOption<"f", "declspec",
 def fmodules_cache_path : Joined<["-"], "fmodules-cache-path=">, Group<i_Group>,
   Flags<[]>, Visibility<[ClangOption, CC1Option]>,
   MetaVarName<"<directory>">,
-  HelpText<"Specify the module cache path">;
+  HelpText<"Specify the module cache path">,
+  MarshallingInfoString<HeaderSearchOpts<"ModuleCachePath">>;
 def fmodules_user_build_path : Separate<["-"], "fmodules-user-build-path">, Group<i_Group>,
   Flags<[]>, Visibility<[ClangOption, CC1Option]>,
   MetaVarName<"<directory>">,

clang/include/clang/Frontend/CompilerInstance.h

@@ -699,6 +699,8 @@ class CompilerInstance : public ModuleLoader {
     GetDependencyDirectives = std::move(Getter);
   }
 
+  static SmallString<256> normalizeModuleCachePath(FileManager &FileMgr,
+                                                   StringRef ModuleCachePath);
   std::string getSpecificModuleCachePath(StringRef ModuleHash);
   std::string getSpecificModuleCachePath() {
     return getSpecificModuleCachePath(getInvocation().getModuleHash());

clang/lib/Frontend/CompilerInstance.cpp

@@ -547,10 +547,25 @@ void CompilerInstance::createPreprocessor(TranslationUnitKind TUKind) {
     PP->setDependencyDirectivesGetter(*GetDependencyDirectives);
 }
 
+SmallString<256>
+CompilerInstance::normalizeModuleCachePath(FileManager &FileMgr,
+                                           StringRef ModuleCachePath) {
+  SmallString<256> NormalizedModuleCachePath(ModuleCachePath);
+  FileMgr.makeAbsolutePath(NormalizedModuleCachePath);
+  llvm::sys::path::remove_dots(NormalizedModuleCachePath);
+  return NormalizedModuleCachePath;
+}
+
 std::string CompilerInstance::getSpecificModuleCachePath(StringRef ModuleHash) {
+  assert(FileMgr && "Specific module cache path requires a FileManager");
+
+  if (getHeaderSearchOpts().ModuleCachePath.empty())
+    return "";
+
   // Set up the module path, including the hash for the module-creation options.
-  SmallString<256> SpecificModuleCache(getHeaderSearchOpts().ModuleCachePath);
-  if (!SpecificModuleCache.empty() && !getHeaderSearchOpts().DisableModuleHash)
+  SmallString<256> SpecificModuleCache =
+      normalizeModuleCachePath(*FileMgr, getHeaderSearchOpts().ModuleCachePath);
+  if (!getHeaderSearchOpts().DisableModuleHash)
     llvm::sys::path::append(SpecificModuleCache, ModuleHash);
   return std::string(SpecificModuleCache);
 }

clang/lib/Frontend/CompilerInvocation.cpp

@@ -3315,9 +3315,6 @@ static void GenerateHeaderSearchArgs(const HeaderSearchOptions &Opts,
   if (Opts.UseLibcxx)
     GenerateArg(Consumer, OPT_stdlib_EQ, "libc++");
 
-  if (!Opts.ModuleCachePath.empty())
-    GenerateArg(Consumer, OPT_fmodules_cache_path, Opts.ModuleCachePath);
-
   for (const auto &File : Opts.PrebuiltModuleFiles)
     GenerateArg(Consumer, OPT_fmodule_file, File.first + "=" + File.second);
 
@@ -3420,8 +3417,7 @@ static void GenerateHeaderSearchArgs(const HeaderSearchOptions &Opts,
 }
 
 static bool ParseHeaderSearchArgs(HeaderSearchOptions &Opts, ArgList &Args,
-                                  DiagnosticsEngine &Diags,
-                                  const std::string &WorkingDir) {
+                                  DiagnosticsEngine &Diags) {
   unsigned NumErrorsBefore = Diags.getNumErrors();
 
   HeaderSearchOptions *HeaderSearchOpts = &Opts;
@@ -3434,17 +3430,6 @@ static bool ParseHeaderSearchArgs(HeaderSearchOptions &Opts, ArgList &Args,
   if (const Arg *A = Args.getLastArg(OPT_stdlib_EQ))
     Opts.UseLibcxx = (strcmp(A->getValue(), "libc++") == 0);
 
-  // Canonicalize -fmodules-cache-path before storing it.
-  SmallString<128> P(Args.getLastArgValue(OPT_fmodules_cache_path));
-  if (!(P.empty() || llvm::sys::path::is_absolute(P))) {
-    if (WorkingDir.empty())
-      llvm::sys::fs::make_absolute(P);
-    else
-      llvm::sys::fs::make_absolute(WorkingDir, P);
-  }
-  llvm::sys::path::remove_dots(P);
-  Opts.ModuleCachePath = std::string(P);
-
   // Only the -fmodule-file=<name>=<file> form.
   for (const auto *A : Args.filtered(OPT_fmodule_file)) {
     StringRef Val = A->getValue();
@@ -5021,8 +5006,7 @@ bool CompilerInvocation::CreateFromArgsImpl(
   InputKind DashX = Res.getFrontendOpts().DashX;
   ParseTargetArgs(Res.getTargetOpts(), Args, Diags);
   llvm::Triple T(Res.getTargetOpts().Triple);
-  ParseHeaderSearchArgs(Res.getHeaderSearchOpts(), Args, Diags,
-                        Res.getFileSystemOpts().WorkingDir);
+  ParseHeaderSearchArgs(Res.getHeaderSearchOpts(), Args, Diags);
   if (Res.getFrontendOpts().GenReducedBMI ||
       Res.getFrontendOpts().ProgramAction ==
           frontend::GenerateReducedModuleInterface ||

clang/lib/Serialization/ASTWriter.cpp

@@ -57,6 +57,7 @@
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Basic/TargetOptions.h"
 #include "clang/Basic/Version.h"
+#include "clang/Frontend/CompilerInstance.h"
 #include "clang/Lex/HeaderSearch.h"
 #include "clang/Lex/HeaderSearchOptions.h"
 #include "clang/Lex/MacroInfo.h"
@@ -1710,9 +1711,12 @@ void ASTWriter::WriteControlBlock(Preprocessor &PP, StringRef isysroot) {
   const HeaderSearchOptions &HSOpts =
       PP.getHeaderSearchInfo().getHeaderSearchOpts();
 
+  auto HSOpts_ModuleCachePath = CompilerInstance::normalizeModuleCachePath(
+      PP.getFileManager(), HSOpts.ModuleCachePath);
+
   AddString(HSOpts.Sysroot, Record);
   AddString(HSOpts.ResourceDir, Record);
-  AddString(HSOpts.ModuleCachePath, Record);
+  AddString(HSOpts_ModuleCachePath, Record);
   AddString(HSOpts.ModuleUserBuildPath, Record);
   Record.push_back(HSOpts.DisableModuleHash);
   Record.push_back(HSOpts.ImplicitModuleMaps);

clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp

@@ -448,9 +448,8 @@ class DependencyScanningAction {
 
     // Use the dependency scanning optimized file system if requested to do so.
     if (DepFS) {
-      StringRef ModulesCachePath =
-          ScanInstance.getHeaderSearchOpts().ModuleCachePath;
-
+      auto ModulesCachePath = CompilerInstance::normalizeModuleCachePath(
+          *FileMgr, ScanInstance.getHeaderSearchOpts().ModuleCachePath);
       DepFS->resetBypassedPathPrefix();
       if (!ModulesCachePath.empty())
         DepFS->setBypassedPathPrefix(ModulesCachePath);

clang/test/Modules/modules-cache-path-canonicalization-output.c

@@ -0,0 +1,18 @@
+// This checks that implicitly-built modules produce identical PCM
+// files regardless of the spelling of the same module cache path.
+
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+
+// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fsyntax-only %t/tu.c \
+// RUN:   -fmodules-cache-path=%t/cache -fdisable-module-hash
+// RUN: mv %t/cache/M.pcm %t/M.pcm
+// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fsyntax-only %t/tu.c \
+// RUN:   -fmodules-cache-path=%t/./cache -fdisable-module-hash
+// RUN: diff %t/./cache/M.pcm %t/M.pcm
+
+//--- tu.c
+#include "M.h"
+//--- M.h
+//--- module.modulemap
+module M { header "M.h" }