[Clang][Lex] Extend HeaderSearch::LookupFile to control OpenFile behavior.

In the case of static compilation the file system is pretty much read-only
and taking a snapshot of it usually is sufficient. In the interactive C++
case the compilation is longer and people can create and include files, etc.
In that case we often do not want to open files or cache failures unless is
absolutely necessary.

This patch extends the original API call by forwarding some optional flags,
so we can continue use it in the previous way with no breakage.
Signed-off-by: Jun Zhang <[email protected]>

Differential Revision: https://reviews.llvm.org/D131241

Author: junaire

clang/include/clang/Lex/DirectoryLookup.h

@@ -186,7 +186,8 @@ class DirectoryLookup {
              SmallVectorImpl<char> *RelativePath, Module *RequestingModule,
              ModuleMap::KnownHeader *SuggestedModule,
              bool &InUserSpecifiedSystemFramework, bool &IsFrameworkFound,
-             bool &IsInHeaderMap, SmallVectorImpl<char> &MappedName) const;
+             bool &IsInHeaderMap, SmallVectorImpl<char> &MappedName,
+             bool OpenFile = true) const;
 
 private:
   Optional<FileEntryRef> DoFrameworkLookup(

clang/include/clang/Lex/HeaderSearch.h

@@ -474,7 +474,8 @@ class HeaderSearch {
       SmallVectorImpl<char> *SearchPath, SmallVectorImpl<char> *RelativePath,
       Module *RequestingModule, ModuleMap::KnownHeader *SuggestedModule,
       bool *IsMapped, bool *IsFrameworkFound, bool SkipCache = false,
-      bool BuildSystemModule = false);
+      bool BuildSystemModule = false, bool OpenFile = true,
+      bool CacheFailures = true);
 
   /// Look up a subframework for the specified \#include file.
   ///
@@ -759,7 +760,8 @@ class HeaderSearch {
   getFileAndSuggestModule(StringRef FileName, SourceLocation IncludeLoc,
                           const DirectoryEntry *Dir, bool IsSystemHeaderDir,
                           Module *RequestingModule,
-                          ModuleMap::KnownHeader *SuggestedModule);
+                          ModuleMap::KnownHeader *SuggestedModule,
+                          bool OpenFile = true, bool CacheFailures = true);
 
   /// Cache the result of a successful lookup at the given include location
   /// using the search path at \c HitIt.

clang/include/clang/Lex/Preprocessor.h

@@ -2228,7 +2228,8 @@ class Preprocessor {
              ConstSearchDirIterator *CurDir, SmallVectorImpl<char> *SearchPath,
              SmallVectorImpl<char> *RelativePath,
              ModuleMap::KnownHeader *SuggestedModule, bool *IsMapped,
-             bool *IsFrameworkFound, bool SkipCache = false);
+             bool *IsFrameworkFound, bool SkipCache = false,
+             bool OpenFile = true, bool CacheFailures = true);
 
   /// Return true if we're in the top-level file, not in a \#include.
   bool isInPrimaryFile() const;

clang/lib/Lex/HeaderSearch.cpp

@@ -398,10 +398,11 @@ StringRef DirectoryLookup::getName() const {
 Optional<FileEntryRef> HeaderSearch::getFileAndSuggestModule(
     StringRef FileName, SourceLocation IncludeLoc, const DirectoryEntry *Dir,
     bool IsSystemHeaderDir, Module *RequestingModule,
-    ModuleMap::KnownHeader *SuggestedModule) {
+    ModuleMap::KnownHeader *SuggestedModule, bool OpenFile /*=true*/,
+    bool CacheFailures /*=true*/) {
   // If we have a module map that might map this header, load it and
   // check whether we'll have a suggestion for a module.
-  auto File = getFileMgr().getFileRef(FileName, /*OpenFile=*/true);
+  auto File = getFileMgr().getFileRef(FileName, OpenFile, CacheFailures);
   if (!File) {
     // For rare, surprising errors (e.g. "out of file handles"), diag the EC
     // message.
@@ -431,7 +432,8 @@ Optional<FileEntryRef> DirectoryLookup::LookupFile(
     SmallVectorImpl<char> *SearchPath, SmallVectorImpl<char> *RelativePath,
     Module *RequestingModule, ModuleMap::KnownHeader *SuggestedModule,
     bool &InUserSpecifiedSystemFramework, bool &IsFrameworkFound,
-    bool &IsInHeaderMap, SmallVectorImpl<char> &MappedName) const {
+    bool &IsInHeaderMap, SmallVectorImpl<char> &MappedName,
+    bool OpenFile) const {
   InUserSpecifiedSystemFramework = false;
   IsInHeaderMap = false;
   MappedName.clear();
@@ -451,9 +453,9 @@ Optional<FileEntryRef> DirectoryLookup::LookupFile(
       RelativePath->append(Filename.begin(), Filename.end());
     }
 
-    return HS.getFileAndSuggestModule(TmpDir, IncludeLoc, getDir(),
-                                      isSystemHeaderDirectory(),
-                                      RequestingModule, SuggestedModule);
+    return HS.getFileAndSuggestModule(
+        TmpDir, IncludeLoc, getDir(), isSystemHeaderDirectory(),
+        RequestingModule, SuggestedModule, OpenFile);
   }
 
   if (isFramework())
@@ -491,7 +493,7 @@ Optional<FileEntryRef> DirectoryLookup::LookupFile(
     Dest = HM->lookupFilename(Filename, Path);
   }
 
-  if (auto Res = HS.getFileMgr().getOptionalFileRef(Dest)) {
+  if (auto Res = HS.getFileMgr().getOptionalFileRef(Dest, OpenFile)) {
     FixupSearchPath();
     return *Res;
   }
@@ -840,7 +842,7 @@ Optional<FileEntryRef> HeaderSearch::LookupFile(
     SmallVectorImpl<char> *SearchPath, SmallVectorImpl<char> *RelativePath,
     Module *RequestingModule, ModuleMap::KnownHeader *SuggestedModule,
     bool *IsMapped, bool *IsFrameworkFound, bool SkipCache,
-    bool BuildSystemModule) {
+    bool BuildSystemModule, bool OpenFile, bool CacheFailures) {
   ConstSearchDirIterator CurDirLocal = nullptr;
   ConstSearchDirIterator &CurDir = CurDirArg ? *CurDirArg : CurDirLocal;
 
@@ -869,8 +871,9 @@ Optional<FileEntryRef> HeaderSearch::LookupFile(
     }
     // Otherwise, just return the file.
     return getFileAndSuggestModule(Filename, IncludeLoc, nullptr,
-                                   /*IsSystemHeaderDir*/false,
-                                   RequestingModule, SuggestedModule);
+                                   /*IsSystemHeaderDir*/ false,
+                                   RequestingModule, SuggestedModule, OpenFile,
+                                   CacheFailures);
   }
 
   // This is the header that MSVC's header search would have found.
@@ -1010,7 +1013,7 @@ Optional<FileEntryRef> HeaderSearch::LookupFile(
     Optional<FileEntryRef> File = It->LookupFile(
         Filename, *this, IncludeLoc, SearchPath, RelativePath, RequestingModule,
         SuggestedModule, InUserSpecifiedSystemFramework, IsFrameworkFoundInDir,
-        IsInHeaderMap, MappedName);
+        IsInHeaderMap, MappedName, OpenFile);
     if (!MappedName.empty()) {
       assert(IsInHeaderMap && "MappedName should come from a header map");
       CacheLookup.MappedName =

clang/lib/Lex/PPDirectives.cpp

@@ -949,7 +949,7 @@ Optional<FileEntryRef> Preprocessor::LookupFile(
     ConstSearchDirIterator *CurDirArg, SmallVectorImpl<char> *SearchPath,
     SmallVectorImpl<char> *RelativePath,
     ModuleMap::KnownHeader *SuggestedModule, bool *IsMapped,
-    bool *IsFrameworkFound, bool SkipCache) {
+    bool *IsFrameworkFound, bool SkipCache, bool OpenFile, bool CacheFailures) {
   ConstSearchDirIterator CurDirLocal = nullptr;
   ConstSearchDirIterator &CurDir = CurDirArg ? *CurDirArg : CurDirLocal;
 
@@ -1028,7 +1028,7 @@ Optional<FileEntryRef> Preprocessor::LookupFile(
   Optional<FileEntryRef> FE = HeaderInfo.LookupFile(
       Filename, FilenameLoc, isAngled, FromDir, &CurDir, Includers, SearchPath,
       RelativePath, RequestingModule, SuggestedModule, IsMapped,
-      IsFrameworkFound, SkipCache, BuildSystemModule);
+      IsFrameworkFound, SkipCache, BuildSystemModule, OpenFile, CacheFailures);
   if (FE) {
     if (SuggestedModule && !LangOpts.AsmPreprocessor)
       HeaderInfo.getModuleMap().diagnoseHeaderInclusion(