[clang] [MinGW] Consider the per-target libc++ include directory too

[mstorsjo]

Summary

The existing logic for per-target libc++ include directories only
seem to exist for the Gnu and Fuchsia drivers, added in
ea12d779bc238c387511fe7462020f4ecf4a8246 / D89013.

This is less generic than the corresponding case in the Gnu driver,
but matches the existing level of genericity in the MinGW driver
(and others too).

[phosek]

LGTM

[zero9178]

Any chance this patch could be backported onto the LLVM 13 branch? I have been using a per target runtime builds for a few versions now but the functionality has regressed in LLVM 13, which would force me back into a normal single target layout.

[mstorsjo]

In D107893#2943679, @zero9178 wrote:

Any chance this patch could be backported onto the LLVM 13 branch? I have been using a per target runtime builds for a few versions now but the functionality has regressed in LLVM 13, which would force me back into a normal single target layout.

I presume this should be pretty trivial to backport yes - can you file a bug about it in bugzilla, CC @tstellar and mark it as blocking the 13.0.0 release bug?

In which way was this a regression - I guess clang didn't change here - did libcxx start installing the __config_site file differently during this release?

[mstorsjo]

In D107893#2944193, @mstorsjo wrote:

In D107893#2943679, @zero9178 wrote:

Any chance this patch could be backported onto the LLVM 13 branch? I have been using a per target runtime builds for a few versions now but the functionality has regressed in LLVM 13, which would force me back into a normal single target layout.

I presume this should be pretty trivial to backport yes - can you file a bug about it in bugzilla, CC @tstellar and mark it as blocking the 13.0.0 release bug?

In which way was this a regression - I guess clang didn't change here - did libcxx start installing the __config_site file differently during this release?

Oh, also, do note that this only fixes the issue for the MinGW driver - this needs to be fixed separately for all drivers it seems (or better - refactor them so they'd use one shared codepath for libc++ includes, fixing it all in one place).

[zero9178]

In D107893#2944193, @mstorsjo wrote:

In D107893#2943679, @zero9178 wrote:

Any chance this patch could be backported onto the LLVM 13 branch? I have been using a per target runtime builds for a few versions now but the functionality has regressed in LLVM 13, which would force me back into a normal single target layout.

I presume this should be pretty trivial to backport yes - can you file a bug about it in bugzilla, CC @tstellar and mark it as blocking the 13.0.0 release bug?

In which way was this a regression - I guess clang didn't change here - did libcxx start installing the __config_site file differently during this release?

Since this release libc++ splits what was previously the __config header into __config_site and __config, where __config_site contains all the defines set at configure time by CMake and gets included by __config. Without this patch the include path to __config_sites directory is missing in per target builds and therefore including any file of libc++ causes a compilation error.

clang/lib/Driver/ToolChains/MinGW.cpp

void toolchains::MinGW::AddClangCXXStdlibIncludeArgs(
     const ArgList &DriverArgs, ArgStringList &CC1Args) const {
   if (DriverArgs.hasArg(options::OPT_nostdlibinc) ||
       DriverArgs.hasArg(options::OPT_nostdincxx))
     return;
 
   StringRef Slash = llvm::sys::path::get_separator();
 
   switch (GetCXXStdlibType(DriverArgs)) {
-  case ToolChain::CST_Libcxx:
+  case ToolChain::CST_Libcxx: {
+    std::string TargetDir = (Base + "include" + Slash + getTripleString() +
+                             Slash + "c++" + Slash + "v1")
+                                .str();
+    if (getDriver().getVFS().exists(TargetDir))
+      addSystemInclude(DriverArgs, CC1Args, TargetDir);
     addSystemInclude(DriverArgs, CC1Args, Base + Arch + Slash + "include" +
                                               Slash + "c++" + Slash + "v1");
     addSystemInclude(DriverArgs, CC1Args,
                      Base + "include" + Slash + "c++" + Slash + "v1");
     break;
+  }
 
   case ToolChain::CST_Libstdcxx:
     llvm::SmallVector<llvm::SmallString<1024>, 4> CppIncludeBases;
     CppIncludeBases.emplace_back(Base);
     llvm::sys::path::append(CppIncludeBases[0], Arch, "include", "c++");
     CppIncludeBases.emplace_back(Base);
     llvm::sys::path::append(CppIncludeBases[1], Arch, "include", "c++", Ver);
     CppIncludeBases.emplace_back(Base);

clang/test/Driver/mingw.cpp

 // RUN: %clang -target i686-windows-gnu -rtlib=platform -c -### --sysroot=%S/Inputs/mingw_clang_tree/mingw32 %s 2>&1 | FileCheck -check-prefix=CHECK_MINGW_CLANG_TREE %s
 // CHECK_MINGW_CLANG_TREE: "[[BASE:[^"]+]]/Inputs/mingw_clang_tree/mingw32{{/|\\\\}}i686-w64-mingw32{{/|\\\\}}include"
 // CHECK_MINGW_CLANG_TREE: "[[BASE]]/Inputs/mingw_clang_tree/mingw32{{/|\\\\}}include"
 
 
 // RUN: %clang -target i686-windows-gnu -rtlib=platform -stdlib=libc++ -c -### --sysroot=%S/Inputs/mingw_clang_tree/mingw32 %s 2>&1 | FileCheck -check-prefix=CHECK_MINGW_CLANG_TREE_LIBCXX %s
+// CHECK_MINGW_CLANG_TREE_LIBCXX: "[[BASE:[^"]+]]/Inputs/mingw_clang_tree/mingw32{{/|\\\\}}include{{/|\\\\}}i686-unknown-windows-gnu{{/|\\\\}}c++{{/|\\\\}}v1"
 // CHECK_MINGW_CLANG_TREE_LIBCXX: "[[BASE:[^"]+]]/Inputs/mingw_clang_tree/mingw32{{/|\\\\}}i686-w64-mingw32{{/|\\\\}}include{{/|\\\\}}c++{{/|\\\\}}v1"
 
 
 // RUN: %clang -target i686-pc-windows-gnu -rtlib=platform -stdlib=libstdc++ -c -### --sysroot=%S/Inputs/mingw_mingw_org_tree/mingw %s 2>&1 | FileCheck -check-prefix=CHECK_MINGW_ORG_TREE %s
 // CHECK_MINGW_ORG_TREE: "[[BASE:[^"]+]]/Inputs/mingw_mingw_org_tree/mingw{{/|\\\\}}lib{{/|\\\\}}gcc{{/|\\\\}}mingw32{{/|\\\\}}4.8.1{{/|\\\\}}include{{/|\\\\}}c++"
 // CHECK_MINGW_ORG_TREE: "[[BASE]]/Inputs/mingw_mingw_org_tree/mingw{{/|\\\\}}lib{{/|\\\\}}gcc{{/|\\\\}}mingw32{{/|\\\\}}4.8.1{{/|\\\\}}include{{/|\\\\}}c++{{/|\\\\}}mingw32"
 // CHECK_MINGW_ORG_TREE: "[[BASE]]/Inputs/mingw_mingw_org_tree/mingw{{/|\\\\}}lib{{/|\\\\}}gcc{{/|\\\\}}mingw32{{/|\\\\}}4.8.1{{/|\\\\}}include{{/|\\\\}}c++{{/|\\\\}}backward"
 // CHECK_MINGW_ORG_TREE: "[[BASE]]/Inputs/mingw_mingw_org_tree/mingw{{/|\\\\}}mingw32{{/|\\\\}}include"