From 1abd4c94d7575e4cd288e0024c1ec79f17b048a9 Mon Sep 17 00:00:00 2001
From: Alexandre Ganea <alexandre.ganea@ubisoft.com>
Date: Thu, 28 Nov 2019 15:56:00 -0500
Subject: [Clang] Bypass distro detection on non-Linux hosts

Skip distro detection when we're not running on Linux, or when the target triple is not Linux. This saves a few OS calls for each invocation of clang.exe.

Differential Revision: https://reviews.llvm.org/D70467
---
 clang/lib/Driver/Distro.cpp           | 22 ++++++++++++++++++++--
 clang/lib/Driver/ToolChains/Clang.cpp |  2 +-
 clang/lib/Driver/ToolChains/Cuda.cpp  |  3 ++-
 clang/lib/Driver/ToolChains/Linux.cpp |  4 ++--
 4 files changed, 25 insertions(+), 6 deletions(-)

(limited to 'clang/lib/Driver')

diff --git a/clang/lib/Driver/Distro.cpp b/clang/lib/Driver/Distro.cpp
index 92e04108a7e..06707fefc9d 100644
--- a/clang/lib/Driver/Distro.cpp
+++ b/clang/lib/Driver/Distro.cpp
@@ -13,11 +13,28 @@
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/ErrorOr.h"
 #include "llvm/Support/MemoryBuffer.h"
+#include "llvm/ADT/Triple.h"
 
 using namespace clang::driver;
 using namespace clang;
 
-static Distro::DistroType DetectDistro(llvm::vfs::FileSystem &VFS) {
+static Distro::DistroType DetectDistro(llvm::vfs::FileSystem &VFS,
+                                       const llvm::Triple &TargetOrHost) {
+  // If we don't target Linux, no need to check the distro. This saves a few
+  // OS calls.
+  if (!TargetOrHost.isOSLinux())
+    return Distro::UnknownDistro;
+
+  // If the host is not running Linux, and we're backed by a real file system,
+  // no need to check the distro. This is the case where someone is
+  // cross-compiling from BSD or Windows to Linux, and it would be meaningless
+  // to try to figure out the "distro" of the non-Linux host.
+  IntrusiveRefCntPtr<llvm::vfs::FileSystem> RealFS =
+      llvm::vfs::getRealFileSystem();
+  llvm::Triple HostTriple(llvm::sys::getProcessTriple());
+  if (!HostTriple.isOSLinux() && &VFS == RealFS.get())
+    return Distro::UnknownDistro;
+
   llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> File =
       VFS.getBufferForFile("/etc/lsb-release");
   if (File) {
@@ -149,4 +166,5 @@ static Distro::DistroType DetectDistro(llvm::vfs::FileSystem &VFS) {
   return Distro::UnknownDistro;
 }
 
-Distro::Distro(llvm::vfs::FileSystem &VFS) : DistroVal(DetectDistro(VFS)) {}
+Distro::Distro(llvm::vfs::FileSystem &VFS, const llvm::Triple &TargetOrHost)
+    : DistroVal(DetectDistro(VFS, TargetOrHost)) {}
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 26d13c71467..03a6de81204 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -5619,7 +5619,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
                     TC.getTriple().isOSBinFormatCOFF()) &&
                       !TC.getTriple().isPS4() &&
                       !TC.getTriple().isOSNetBSD() &&
-                      !Distro(D.getVFS()).IsGentoo() &&
+                      !Distro(D.getVFS(), TC.getTriple()).IsGentoo() &&
                       !TC.getTriple().isAndroid() &&
                        TC.useIntegratedAs()))
     CmdArgs.push_back("-faddrsig");
diff --git a/clang/lib/Driver/ToolChains/Cuda.cpp b/clang/lib/Driver/ToolChains/Cuda.cpp
index 8c704a3078a..02871d2ce41 100644
--- a/clang/lib/Driver/ToolChains/Cuda.cpp
+++ b/clang/lib/Driver/ToolChains/Cuda.cpp
@@ -115,7 +115,8 @@ CudaInstallationDetector::CudaInstallationDetector(
     for (const char *Ver : Versions)
       Candidates.emplace_back(D.SysRoot + "/usr/local/cuda-" + Ver);
 
-    if (Distro(D.getVFS()).IsDebian() || Distro(D.getVFS()).IsUbuntu())
+    Distro Dist(D.getVFS(), llvm::Triple(llvm::sys::getProcessTriple()));
+    if (Dist.IsDebian() || Dist.IsUbuntu())
       // Special case for Debian to have nvidia-cuda-toolkit work
       // out of the box. More info on http://bugs.debian.org/882505
       Candidates.emplace_back(D.SysRoot + "/usr/lib/cuda");
diff --git a/clang/lib/Driver/ToolChains/Linux.cpp b/clang/lib/Driver/ToolChains/Linux.cpp
index 087783875ff..736a2d435ca 100644
--- a/clang/lib/Driver/ToolChains/Linux.cpp
+++ b/clang/lib/Driver/ToolChains/Linux.cpp
@@ -240,7 +240,7 @@ Linux::Linux(const Driver &D, const llvm::Triple &Triple, const ArgList &Args)
                          .str());
   }
 
-  Distro Distro(D.getVFS());
+  Distro Distro(D.getVFS(), Triple);
 
   if (Distro.IsAlpineLinux() || Triple.isAndroid()) {
     ExtraOpts.push_back("-z");
@@ -511,7 +511,7 @@ std::string Linux::getDynamicLinker(const ArgList &Args) const {
   const llvm::Triple::ArchType Arch = getArch();
   const llvm::Triple &Triple = getTriple();
 
-  const Distro Distro(getDriver().getVFS());
+  const Distro Distro(getDriver().getVFS(), Triple);
 
   if (Triple.isAndroid())
     return Triple.isArch64Bit() ? "/system/bin/linker64" : "/system/bin/linker";
-- 
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