Multilib support for libraries with exceptions (#75031)

For better multilib matching explicitly match -fno-rtti and -fno-exceptions

Author: pwprzybyla

clang/include/clang/Driver/ToolChain.h

@@ -120,6 +120,11 @@ class ToolChain {
     RM_Disabled,
   };
 
+  enum ExceptionsMode {
+    EM_Enabled,
+    EM_Disabled,
+  };
+
   struct BitCodeLibraryInfo {
     std::string Path;
     bool ShouldInternalize;
@@ -141,6 +146,8 @@ class ToolChain {
 
   const RTTIMode CachedRTTIMode;
 
+  const ExceptionsMode CachedExceptionsMode;
+
   /// The list of toolchain specific path prefixes to search for libraries.
   path_list LibraryPaths;
 
@@ -318,6 +325,9 @@ class ToolChain {
   // Returns the RTTIMode for the toolchain with the current arguments.
   RTTIMode getRTTIMode() const { return CachedRTTIMode; }
 
+  // Returns the ExceptionsMode for the toolchain with the current arguments.
+  ExceptionsMode getExceptionsMode() const { return CachedExceptionsMode; }
+
   /// Return any implicit target and/or mode flag for an invocation of
   /// the compiler driver as `ProgName`.
   ///

clang/lib/Driver/ToolChain.cpp

@@ -77,10 +77,19 @@ static ToolChain::RTTIMode CalculateRTTIMode(const ArgList &Args,
   return NoRTTI ? ToolChain::RM_Disabled : ToolChain::RM_Enabled;
 }
 
+static ToolChain::ExceptionsMode CalculateExceptionsMode(const ArgList &Args) {
+  if (Args.hasFlag(options::OPT_fexceptions, options::OPT_fno_exceptions,
+                   true)) {
+    return ToolChain::EM_Enabled;
+  }
+  return ToolChain::EM_Disabled;
+}
+
 ToolChain::ToolChain(const Driver &D, const llvm::Triple &T,
                      const ArgList &Args)
     : D(D), Triple(T), Args(Args), CachedRTTIArg(GetRTTIArgument(Args)),
-      CachedRTTIMode(CalculateRTTIMode(Args, Triple, CachedRTTIArg)) {
+      CachedRTTIMode(CalculateRTTIMode(Args, Triple, CachedRTTIArg)),
+      CachedExceptionsMode(CalculateExceptionsMode(Args)) {
   auto addIfExists = [this](path_list &List, const std::string &Path) {
     if (getVFS().exists(Path))
       List.push_back(Path);
@@ -264,6 +273,18 @@ ToolChain::getMultilibFlags(const llvm::opt::ArgList &Args) const {
     break;
   }
 
+  // Include fno-exceptions and fno-rtti
+  // to improve multilib selection
+  if (getRTTIMode() == ToolChain::RTTIMode::RM_Disabled)
+    Result.push_back("-fno-rtti");
+  else
+    Result.push_back("-frtti");
+
+  if (getExceptionsMode() == ToolChain::ExceptionsMode::EM_Disabled)
+    Result.push_back("-fno-exceptions");
+  else
+    Result.push_back("-fexceptions");
+
   // Sort and remove duplicates.
   std::sort(Result.begin(), Result.end());
   Result.erase(std::unique(Result.begin(), Result.end()), Result.end());