dmantipov created this revision.
dmantipov added reviewers: mgorny, aganea.
dmantipov added a project: clang.
Herald added a subscriber: cfe-commits.
dmantipov requested review of this revision.
When running regular ('clang++ foo.cc') native compilation on Linux target in a
typical configuration, an attempt to detect distribution type is performed 4
times at least:
- during an attempt to detect CUDA installation in
clang::driver::CudaInstallationDetector::CudaInstallationDetector();
- during an instantiation of Linux-specific toolchain driver
(clang::driver::toolchains::Linux::Linux());
- when special handling of '-faddrsig' is performed in
clang::driver::tools::Clang::ConstructJob();
- finally when constructing a linker job in
clang::driver::toolchains::Linux::getDynamicLinker().
Since distribution detection involves VFS, filesystem I/O and even parsing of
file(s) contents, it looks desirable to cache the result and perform the whole
procedure just once.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D87187
Files:
clang/include/clang/Driver/Distro.h
clang/lib/Driver/Distro.cpp
Index: clang/lib/Driver/Distro.cpp
===================================================================
--- clang/lib/Driver/Distro.cpp
+++ clang/lib/Driver/Distro.cpp
@@ -21,20 +21,10 @@
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;
+ // We're definitely on Linux, so start looking for the filesystem artifacts.
+ // TODO: adjust this to match modern freedesktop.org's compilant system
+ // with /etc/os-release and/or /usr/lib/os-release. For the details,
+ // see https://www.freedesktop.org/software/systemd/man/os-release.html.
llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> File =
VFS.getBufferForFile("/etc/lsb-release");
@@ -168,5 +158,36 @@
return Distro::UnknownDistro;
}
+static Distro::DistroType GetDistro(llvm::vfs::FileSystem &VFS,
+ const llvm::Triple &TargetOrHost) {
+ static Distro::DistroType Type = Distro::UninitializedDistro;
+
+ // 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 we perform the detection already, return the result. This saves a few
+ // more OS calls assuming there was no underlying on-the fly distro change.
+ if (Type != Distro::UninitializedDistro)
+ return Type;
+
+ // 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())
+ Type = Distro::UnknownDistro;
+ else
+ // Perform the detection and save the result.
+ Type = DetectDistro(VFS, TargetOrHost);
+
+ return Type;
+}
+
Distro::Distro(llvm::vfs::FileSystem &VFS, const llvm::Triple &TargetOrHost)
- : DistroVal(DetectDistro(VFS, TargetOrHost)) {}
+ : DistroVal(GetDistro(VFS, TargetOrHost)) {}
Index: clang/include/clang/Driver/Distro.h
===================================================================
--- clang/include/clang/Driver/Distro.h
+++ clang/include/clang/Driver/Distro.h
@@ -23,6 +23,8 @@
class Distro {
public:
enum DistroType {
+ // Special value means that no detection was performed yet.
+ UninitializedDistro = -1,
// NB: Releases of a particular Linux distro should be kept together
// in this enum, because some tests are done by integer comparison against
// the first and last known member in the family, e.g. IsRedHat().
Index: clang/lib/Driver/Distro.cpp
===================================================================
--- clang/lib/Driver/Distro.cpp
+++ clang/lib/Driver/Distro.cpp
@@ -21,20 +21,10 @@
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;
+ // We're definitely on Linux, so start looking for the filesystem artifacts.
+ // TODO: adjust this to match modern freedesktop.org's compilant system
+ // with /etc/os-release and/or /usr/lib/os-release. For the details,
+ // see https://www.freedesktop.org/software/systemd/man/os-release.html.
llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> File =
VFS.getBufferForFile("/etc/lsb-release");
@@ -168,5 +158,36 @@
return Distro::UnknownDistro;
}
+static Distro::DistroType GetDistro(llvm::vfs::FileSystem &VFS,
+ const llvm::Triple &TargetOrHost) {
+ static Distro::DistroType Type = Distro::UninitializedDistro;
+
+ // 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 we perform the detection already, return the result. This saves a few
+ // more OS calls assuming there was no underlying on-the fly distro change.
+ if (Type != Distro::UninitializedDistro)
+ return Type;
+
+ // 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())
+ Type = Distro::UnknownDistro;
+ else
+ // Perform the detection and save the result.
+ Type = DetectDistro(VFS, TargetOrHost);
+
+ return Type;
+}
+
Distro::Distro(llvm::vfs::FileSystem &VFS, const llvm::Triple &TargetOrHost)
- : DistroVal(DetectDistro(VFS, TargetOrHost)) {}
+ : DistroVal(GetDistro(VFS, TargetOrHost)) {}
Index: clang/include/clang/Driver/Distro.h
===================================================================
--- clang/include/clang/Driver/Distro.h
+++ clang/include/clang/Driver/Distro.h
@@ -23,6 +23,8 @@
class Distro {
public:
enum DistroType {
+ // Special value means that no detection was performed yet.
+ UninitializedDistro = -1,
// NB: Releases of a particular Linux distro should be kept together
// in this enum, because some tests are done by integer comparison against
// the first and last known member in the family, e.g. IsRedHat().
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
