From 5e5d21462d1ea7dbaa13bcd9bcf0156cee45b97c Mon Sep 17 00:00:00 2001
From: Manoj Gupta <manojgupta@google.com>
Date: Thu, 22 Sep 2022 13:53:46 -0700
Subject: [PATCH] BareMetal: detect usr/include/c++/v1 path in sysroot

Currently baremetal driver adds <sysroot>/include/c++/v1
for libc++ headers. However on ChromeOS, all include files
are inside <sysroot>/usr/include. So add
<sysroot>/usr/include/c++/v1 if it exists in baremetal driver.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D134478
---
 clang/lib/Driver/ToolChains/BareMetal.cpp | 14 +++++++++++---
 clang/test/Driver/baremetal.cpp           | 16 ++++++++++++++++
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/clang/lib/Driver/ToolChains/BareMetal.cpp b/clang/lib/Driver/ToolChains/BareMetal.cpp
index 7b4b5a35205f..135843463b00 100644
--- a/clang/lib/Driver/ToolChains/BareMetal.cpp
+++ b/clang/lib/Driver/ToolChains/BareMetal.cpp
@@ -217,12 +217,21 @@ void BareMetal::AddClangCXXStdlibIncludeArgs(const ArgList &DriverArgs,
       DriverArgs.hasArg(options::OPT_nostdincxx))
     return;
 
+  const Driver &D = getDriver();
   std::string SysRoot(computeSysRoot());
   if (SysRoot.empty())
     return;
 
   switch (GetCXXStdlibType(DriverArgs)) {
   case ToolChain::CST_Libcxx: {
+    // First check sysroot/usr/include/c++/v1 if it exists.
+    SmallString<128> TargetDir(SysRoot);
+    llvm::sys::path::append(TargetDir, "usr", "include", "c++", "v1");
+    if (D.getVFS().exists(TargetDir)) {
+      addSystemInclude(DriverArgs, CC1Args, TargetDir.str());
+      break;
+    }
+    // Add generic path if nothing else succeeded so far.
     SmallString<128> Dir(SysRoot);
     llvm::sys::path::append(Dir, "include", "c++", "v1");
     addSystemInclude(DriverArgs, CC1Args, Dir.str());
@@ -234,9 +243,8 @@ void BareMetal::AddClangCXXStdlibIncludeArgs(const ArgList &DriverArgs,
     std::error_code EC;
     Generic_GCC::GCCVersion Version = {"", -1, -1, -1, "", "", ""};
     // Walk the subdirs, and find the one with the newest gcc version:
-    for (llvm::vfs::directory_iterator
-             LI = getDriver().getVFS().dir_begin(Dir.str(), EC),
-             LE;
+    for (llvm::vfs::directory_iterator LI = D.getVFS().dir_begin(Dir.str(), EC),
+                                       LE;
          !EC && LI != LE; LI = LI.increment(EC)) {
       StringRef VersionText = llvm::sys::path::filename(LI->path());
       auto CandidateVersion = Generic_GCC::GCCVersion::Parse(VersionText);
diff --git a/clang/test/Driver/baremetal.cpp b/clang/test/Driver/baremetal.cpp
index aded91915609..b5fc45586908 100644
--- a/clang/test/Driver/baremetal.cpp
+++ b/clang/test/Driver/baremetal.cpp
@@ -77,6 +77,22 @@
 // CHECK-V6M-NDL-SAME: "-L{{[^"]*}}{{[/\\]+}}Inputs{{[/\\]+}}baremetal_arm{{[/\\]+}}lib"
 // CHECK-V6M-NDL-SAME: "-L[[RESOURCE_DIR]]{{[/\\]+}}lib{{[/\\]+}}baremetal"
 
+// RUN: rm -rf %T/baremetal_cxx_sysroot
+// RUN: mkdir -p %T/baremetal_cxx_sysroot/usr/include/c++/v1
+// RUN: %clangxx %s -### 2>&1 \
+// RUN:     --target=armv6m-none-eabi \
+// RUN:     --sysroot=%T/baremetal_cxx_sysroot \
+// RUN:     -stdlib=libc++ \
+// RUN:   | FileCheck --check-prefix=CHECK-V6M-LIBCXX-USR %s
+// CHECK-V6M-LIBCXX-USR: "-resource-dir" "[[RESOURCE_DIR:[^"]+]]"
+// CHECK-V6M-LIBCXX-USR-NOT: "-internal-isystem" "{{[^"]+}}baremetal_cxx_sysroot{{[/\\]+}}include{{[/\\]+}}c++{{[/\\]+}}{{[^v].*}}"
+// CHECK-V6M-LIBCXX-USR-SAME: "-internal-isystem" "{{[^"]+}}baremetal_cxx_sysroot{{[/\\]+}}usr{{[/\\]+}}include{{[/\\]+}}c++{{[/\\]+}}v1"
+// CHECK-V6M-LIBCXX-USR: "{{[^"]*}}-Bstatic"
+// CHECK-V6M-LIBCXX-USR-SAME: "-L{{[^"]*}}{{[/\\]+}}baremetal_cxx_sysroot{{[/\\]+}}lib"
+// CHECK-V6M-LIBCXX-USR-SAME: "-L[[RESOURCE_DIR]]{{[/\\]+}}lib{{[/\\]+}}baremetal"
+// CHECK-V6M-LIBCXX-USR-SAME: "-lc++" "-lc++abi" "-lunwind"
+// CHECK-V6M-LIBCXX-USR-SAME: "-lc" "-lm" "-lclang_rt.builtins-armv6m"
+
 // RUN: %clangxx --target=arm-none-eabi -v 2>&1 \
 // RUN:   | FileCheck %s --check-prefix=CHECK-THREAD-MODEL
 // CHECK-THREAD-MODEL: Thread model: posix