clang: Exherbo multiarch ajustments

[Keruspe]

Summary

Exherbo multiarch layout being somewhat specific, some adjustments need to be made wrt the lookup paths.

Based in parts on patches by Marvin Schmidt

[Keruspe]

Make Exherbo multiarch integration more similar to the debian one

[Keruspe]

Mark some tests as XFAIL on exherbo because the filesystem layout is different

[compnerd]

The test adjustments are incorrect. They should optionally accept the triple in the path.

clang/lib/Driver/ToolChains/Linux.cpp

360

Could you use llvm::sys::path::stem please?

889

Why not just always construct the path? "/usr/" + getTriple.str() + "/include" is always going to be the path that we have for exherbo

984

Why is this part of the if? This should be part of the code executed conditionally.

[Keruspe]

Will give llvm::sys::path::stem a look and try to drop the x86_64 part from the include dir selection

clang/lib/Driver/ToolChains/Linux.cpp

360

This was just a copy of the code that as already there, with a different path, but I sure can give that a look

889

That's what we had at first, but then e.g. clang -m32 didn't work as it was searching inside of i383 and not i686, and wrt x86_64 it was using unknown at some point instead of pc.
The x86_64 part might have been because it was in another environment but the x86 part definitely is still relevant

984

It just matches the if from below, with the distro check added. Not familiar with the llvm codebase so I'm trying to just stick to the similar code that's just next to it

clang/lib/Driver/ToolChains/Linux.cpp

     //
     // Note that this matches the GCC behavior. See the below comment for where
     // Clang diverges from GCC's behavior.
-    addPathIfExists(D, LibPath + "/../" + GCCTriple.str() + "/lib/../" +
-                           OSLibDir + SelectedMultilib.osSuffix(),
-                    Paths);
+    //
+    // On Exherbo, the GCC installation will reside in e.g.
+    //   /usr/x86_64-pc-linux-gnu/lib/gcc/armv7-unknown-linux-gnueabihf/9.2.0
+    // while the matching lib path is
+    //   /usr/armv7-unknown-linux-gnueabihf/lib
+    if (Distro == Distro::Exherbo)
+      addPathIfExists(D,
+                      LibPath + "/../../" + GCCTriple.str() + "/lib/../" +
+                          OSLibDir + SelectedMultilib.osSuffix(),
+                      Paths);
+    else
+      addPathIfExists(D,
+                      LibPath + "/../" + GCCTriple.str() + "/lib/../" +
+                          OSLibDir + SelectedMultilib.osSuffix(),
+                      Paths);
 
     // If the GCC installation we found is inside of the sysroot, we want to
     // prefer libraries installed in the parent prefix of the GCC installation.

   if (getTriple().isAndroid())
     MultiarchIncludeDirs = AndroidMultiarchIncludeDirs;
 
+  // Exherbo's multiarch layout is /usr/<triple>/include and not
+  // /usr/include/<triple>
+  const Distro Distro(D.getVFS());
+  const StringRef ExherboMultiarchIncludeDirs[] = {"/usr/" + getTriple().str() +
+                                                   "/include"};
+  const StringRef ExherboX86_64MuslMultiarchIncludeDirs[] = {
+      "/usr/x86_64-pc-linux-musl/include"};
+  const StringRef ExherboX86_64MultiarchIncludeDirs[] = {
+      "/usr/x86_64-pc-linux-gnu/include"};
+  const StringRef ExherboI686MuslMultiarchIncludeDirs[] = {
+      "/usr/i686-pc-linux-musl/include"};
+  const StringRef ExherboI686MultiarchIncludeDirs[] = {
+      "/usr/i686-pc-linux-gnu/include"};
+  if (Distro == Distro::Exherbo) {
+    switch (getTriple().getArch()) {
+    case llvm::Triple::x86_64:
+      if (getTriple().isMusl())
+        MultiarchIncludeDirs = ExherboX86_64MuslMultiarchIncludeDirs;
+      else
+        MultiarchIncludeDirs = ExherboX86_64MultiarchIncludeDirs;
+      break;
+    case llvm::Triple::x86:
+      if (getTriple().isMusl())
+        MultiarchIncludeDirs = ExherboI686MuslMultiarchIncludeDirs;
+      else
+        MultiarchIncludeDirs = ExherboI686MultiarchIncludeDirs;
+      break;
+    default:
+      MultiarchIncludeDirs = ExherboMultiarchIncludeDirs;
+      break;
+    }
+  }
+
   for (StringRef Dir : MultiarchIncludeDirs) {
     if (D.getVFS().exists(SysRoot + Dir)) {
       addExternCSystemInclude(DriverArgs, CC1Args, SysRoot + Dir);

   StringRef LibDir = GCCInstallation.getParentLibPath();
   StringRef InstallDir = GCCInstallation.getInstallPath();
   StringRef TripleStr = GCCInstallation.getTriple().str();
+  const Driver &D = getDriver();
   const Multilib &Multilib = GCCInstallation.getMultilib();
-  const std::string GCCMultiarchTriple = getMultiarchTriple(
-      getDriver(), GCCInstallation.getTriple(), getDriver().SysRoot);
+  const std::string GCCMultiarchTriple =
+      getMultiarchTriple(D, GCCInstallation.getTriple(), D.SysRoot);
   const std::string TargetMultiarchTriple =
-      getMultiarchTriple(getDriver(), getTriple(), getDriver().SysRoot);
+      getMultiarchTriple(D, getTriple(), D.SysRoot);
   const GCCVersion &Version = GCCInstallation.getVersion();
+  const Distro Distro(D.getVFS());
+
+  // On Exherbo the consecutive addLibStdCXXIncludePaths call would evaluate to:
+  //   LibDir = /usr/lib/gcc/<triple>/9.2.0/../../..
+  //          = /usr/lib/
+  //   LibDir + "/../include" = /usr/include
+  // addLibStdCXXIncludePaths would then check if "/usr/include/c++/<version>"
+  // exists, and add that as include path when what we want is
+  // "/usr/<triple>/include/c++/<version>"
+  // Note that "/../../" is needed and not just "/../" as /usr/include points to
+  // /usr/host/include
+  if (Distro == Distro::Exherbo &&
+      addLibStdCXXIncludePaths(
+          LibDir.str() + "/../../" + TripleStr + "/include",
+          "/c++/" + Version.Text, TripleStr, GCCMultiarchTriple,
+          TargetMultiarchTriple, Multilib.includeSuffix(), DriverArgs, CC1Args))
+    return;
 
   // The primary search for libstdc++ supports multiarch variants.
   if (addLibStdCXXIncludePaths(LibDir.str() + "/../include",