Hurd: Clean up Debian multiarch /usr/include/<triplet>

[sthibaul]

Summary

This is a follow-up of 35dd6470de84 for the Hurd case, to avoid the
duplication of the i386-gnu path, already provided by
Hurd::getMultiarchTriple.

[MaskRay]

Thanks!

[sthibaul]

FI, I don't have commit access.

[MaskRay]

Does Hurd support non-i386? Ideally this should have a test.

[sthibaul]

No, for now it only supports i686.
This part is actually already being tested by hurd.cpp, /usr/include/i386-gnu wouldn't be getting included otherwise.

[MaskRay]

I see that this makes the code similar to the similar logic in Linux.cpp. Thanks!

[sthibaul]

I try to make Hurd.cpp close to Linux.cpp in general, yes.

clang/lib/Driver/ToolChains/Hurd.cpp

if (CIncludeDirs != "") {
     return;
   }
 
   // Lacking those, try to detect the correct set of system includes for the
   // target triple.
 
   AddMultilibIncludeArgs(DriverArgs, CC1Args);
 
-  if (getTriple().getArch() == llvm::Triple::x86) {
-    std::string Path = SysRoot + "/usr/include/i386-gnu";
-    if (D.getVFS().exists(Path))
-      addExternCSystemInclude(DriverArgs, CC1Args, Path);
-  }
+  // On systems using multiarch, add /usr/include/$triple before
+  // /usr/include.
+  std::string MultiarchIncludeDir = getMultiarchTriple(D, getTriple(), SysRoot);
+  if (!MultiarchIncludeDir.empty() &&
+      D.getVFS().exists(SysRoot + "/usr/include/" + MultiarchIncludeDir))
+    addExternCSystemInclude(DriverArgs, CC1Args,
+                            SysRoot + "/usr/include/" + MultiarchIncludeDir);
 
   // Add an include of '/include' directly. This isn't provided by default by
   // system GCCs, but is often used with cross-compiling GCCs, and harmless to
   // add even when Clang is acting as-if it were a system compiler.
   addExternCSystemInclude(DriverArgs, CC1Args, SysRoot + "/include");
 
   addExternCSystemInclude(DriverArgs, CC1Args, SysRoot + "/usr/include");
 }