Introduce -fmodules-ignore-macro=NNN to ignore a macro when building/loading modules.

The use of this flag enables a modules optimization where a given set
of macros can be labeled as "ignored" by the modules
system. Definitions of those macros will be completely ignored when
building the module hash and will be stripped when actually building
modules. The overall effect is that this flag can be used to
drastically reduce the number of

Eventually, we'll want modules to tell us what set of macros they
respond to (the "configuration macros"), and anything not in that set
will be excluded. However, that requires a lot of per-module
information that must be accurate, whereas this option can be used
more readily.

Fixes the rest of <rdar://problem/13165109>.

llvm-svn: 174560

1 files changed, 22 insertions, 2 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index a4597fd..34496ed 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -813,7 +813,13 @@ static void ParseHeaderSearchArgs(HeaderSearchOptions &Opts, ArgList &Args) {
   Opts.ResourceDir = Args.getLastArgValue(OPT_resource_dir);
   Opts.ModuleCachePath = Args.getLastArgValue(OPT_fmodule_cache_path);
   Opts.DisableModuleHash = Args.hasArg(OPT_fdisable_module_hash);
-  
+
+  for (arg_iterator it = Args.filtered_begin(OPT_fmodules_ignore_macro),
+       ie = Args.filtered_end(); it != ie; ++it) {
+    const Arg *A = *it;
+    Opts.ModulesIgnoreMacros.insert(A->getValue());
+  }
+
   // Add -I..., -F..., and -index-header-map options in order.
   bool IsIndexHeaderMap = false;
   for (arg_iterator it = Args.filtered_begin(OPT_I, OPT_F, 
@@ -1600,6 +1606,7 @@ std::string CompilerInvocation::getModuleHash() const {
 
   // Extend the signature with preprocessor options.
   const PreprocessorOptions &ppOpts = getPreprocessorOpts();
+  const HeaderSearchOptions &hsOpts = getHeaderSearchOpts();
   code = hash_combine(code, ppOpts.UsePredefines, ppOpts.DetailedRecord);
 
   std::vector<StringRef> MacroDefs;
@@ -1607,11 +1614,24 @@ std::string CompilerInvocation::getModuleHash() const {
             I = getPreprocessorOpts().Macros.begin(),
          IEnd = getPreprocessorOpts().Macros.end();
        I != IEnd; ++I) {
+    // If we're supposed to ignore this macro for the purposes of modules,
+    // don't put it into the hash.
+    if (!hsOpts.ModulesIgnoreMacros.empty()) {
+      // Dig out the macro name.
+      StringRef MacroName = I->first;
+      StringRef::size_type EqPos = MacroName.find('=');
+      if (EqPos != StringRef::npos)
+        MacroName = MacroName.substr(0, EqPos);
+
+      // Check whether we're ignoring this macro.
+      if (hsOpts.ModulesIgnoreMacros.count(MacroName))
+        continue;
+    }
+
     code = hash_combine(code, I->first, I->second);
   }
 
   // Extend the signature with the sysroot.
-  const HeaderSearchOptions &hsOpts = getHeaderSearchOpts();
   code = hash_combine(code, hsOpts.Sysroot, hsOpts.UseBuiltinIncludes,
                       hsOpts.UseStandardSystemIncludes,
                       hsOpts.UseStandardCXXIncludes,