From d882ca7f1f1dee7d812d6b1ae060b5f671ab9ebc Mon Sep 17 00:00:00 2001
From: Dmitry Antipov <dmantipov@yandex.ru>
Date: Wed, 23 Sep 2020 20:21:18 +0300
Subject: [PATCH] [Driver] Check whether Gentoo-specific configuration
 directory exists

Check whether /etc/env.d/gcc exists before trying to read from any
file from there. This saves a few OS calls on a non-Gentoo system.

Differential Revision: https://reviews.llvm.org/D87143
---
 clang/lib/Driver/ToolChains/Gnu.cpp | 7 +++++--
 clang/lib/Driver/ToolChains/Gnu.h   | 3 +++
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Driver/ToolChains/Gnu.cpp b/clang/lib/Driver/ToolChains/Gnu.cpp
index 68a75db..64ae5ac 100644
--- a/clang/lib/Driver/ToolChains/Gnu.cpp
+++ b/clang/lib/Driver/ToolChains/Gnu.cpp
@@ -2535,6 +2535,9 @@ bool Generic_GCC::GCCInstallationDetector::ScanGentooConfigs(
     const llvm::Triple &TargetTriple, const ArgList &Args,
     const SmallVectorImpl<StringRef> &CandidateTriples,
     const SmallVectorImpl<StringRef> &CandidateBiarchTriples) {
+  if (!D.getVFS().exists(D.SysRoot + GentooConfigDir))
+    return false;
+
   for (StringRef CandidateTriple : CandidateTriples) {
     if (ScanGentooGccConfig(TargetTriple, Args, CandidateTriple))
       return true;
@@ -2551,7 +2554,7 @@ bool Generic_GCC::GCCInstallationDetector::ScanGentooGccConfig(
     const llvm::Triple &TargetTriple, const ArgList &Args,
     StringRef CandidateTriple, bool NeedsBiarchSuffix) {
   llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> File =
-      D.getVFS().getBufferForFile(D.SysRoot + "/etc/env.d/gcc/config-" +
+      D.getVFS().getBufferForFile(D.SysRoot + GentooConfigDir + "/config-" +
                                   CandidateTriple.str());
   if (File) {
     SmallVector<StringRef, 2> Lines;
@@ -2563,7 +2566,7 @@ bool Generic_GCC::GCCInstallationDetector::ScanGentooGccConfig(
         continue;
       // Process the config file pointed to by CURRENT.
       llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> ConfigFile =
-          D.getVFS().getBufferForFile(D.SysRoot + "/etc/env.d/gcc/" +
+          D.getVFS().getBufferForFile(D.SysRoot + GentooConfigDir + "/" +
                                       Line.str());
       std::pair<StringRef, StringRef> ActiveVersion = Line.rsplit('-');
       // List of paths to scan for libraries.
diff --git a/clang/lib/Driver/ToolChains/Gnu.h b/clang/lib/Driver/ToolChains/Gnu.h
index 52690ab..5f3d1be 100644
--- a/clang/lib/Driver/ToolChains/Gnu.h
+++ b/clang/lib/Driver/ToolChains/Gnu.h
@@ -212,6 +212,9 @@ public:
     /// The set of multilibs that the detected installation supports.
     MultilibSet Multilibs;
 
+    // Gentoo-specific toolchain configurations are stored here.
+    const std::string GentooConfigDir = "/etc/env.d/gcc";
+
   public:
     explicit GCCInstallationDetector(const Driver &D) : IsValid(false), D(D) {}
     void init(const llvm::Triple &TargetTriple, const llvm::opt::ArgList &Args,
-- 
2.7.4