Merge System into Support.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120298 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/Unix/Host.inc b/lib/Support/Unix/Host.inc
new file mode 100644
index 0000000..ca0de9c
--- /dev/null
+++ b/lib/Support/Unix/Host.inc
@@ -0,0 +1,96 @@
+ //===- llvm/System/Unix/Host.inc -------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the UNIX Host support.
+//
+//===----------------------------------------------------------------------===//
+
+//===----------------------------------------------------------------------===//
+//=== WARNING: Implementation here must contain only generic UNIX code that
+//===          is guaranteed to work on *all* UNIX variants.
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Config/config.h"
+#include "llvm/ADT/StringRef.h"
+#include "Unix.h"
+#include <sys/utsname.h>
+#include <string>
+
+using namespace llvm;
+
+static std::string getOSVersion() {
+  struct utsname info;
+
+  if (uname(&info))
+    return "";
+
+  return info.release;
+}
+
+std::string sys::getHostTriple() {
+  // FIXME: Derive directly instead of relying on the autoconf generated
+  // variable.
+
+  StringRef HostTripleString(LLVM_HOSTTRIPLE);
+  std::pair<StringRef, StringRef> ArchSplit = HostTripleString.split('-');
+
+  // Normalize the arch, since the host triple may not actually match the host.
+  std::string Arch = ArchSplit.first;
+
+  // It would be nice to do this in terms of llvm::Triple, but that is in
+  // Support which is layered above us.
+#if defined(__x86_64__)
+  Arch = "x86_64";
+#elif defined(__i386__)
+  Arch = "i386";
+#elif defined(__ppc64__)
+  Arch = "powerpc64";
+#elif defined(__ppc__)
+  Arch = "powerpc";
+#elif defined(__arm__)
+
+  // FIXME: We need to pick the right ARM triple (which involves querying the
+  // chip). However, for now this is most important for LLVM arch selection, so
+  // we only need to make sure to distinguish ARM and Thumb.
+#  if defined(__thumb__)
+  Arch = "thumb";
+#  else
+  Arch = "arm";
+#  endif
+
+#else
+
+  // FIXME: When enough auto-detection is in place, this should just
+  // #error. Then at least the arch selection is done, and we only need the OS
+  // etc selection to kill off the use of LLVM_HOSTTRIPLE.
+
+#endif
+
+  std::string Triple(Arch);
+  Triple += '-';
+  Triple += ArchSplit.second;
+
+  // Force i<N>86 to i386.
+  if (Triple[0] == 'i' && isdigit(Triple[1]) &&
+      Triple[2] == '8' && Triple[3] == '6')
+    Triple[1] = '3';
+
+  // On darwin, we want to update the version to match that of the
+  // host.
+  std::string::size_type DarwinDashIdx = Triple.find("-darwin");
+  if (DarwinDashIdx != std::string::npos) {
+    Triple.resize(DarwinDashIdx + strlen("-darwin"));
+
+    // Only add the major part of the os version.
+    std::string Version = getOSVersion();
+    Triple += Version.substr(0, Version.find('.'));
+  }
+
+  return Triple;
+}