Improve llvm::getHostTriple for some cases where the LLVM_HOSTTRIPLE is not

reliable.

llvm-svn: 80863

lib/System/Unix/Host.inc

@@ -16,7 +16,8 @@
 //===          is guaranteed to work on *all* UNIX variants.
 //===----------------------------------------------------------------------===//
 
-#include <llvm/Config/config.h>
+#include "llvm/Config/config.h"
+#include "llvm/ADT/StringRef.h"
 #include "Unix.h"
 #include <sys/utsname.h>
 #include <string>
@@ -33,10 +34,47 @@ static std::string getOSVersion() {
 }
 
 std::string sys::getHostTriple() {
-  // FIXME: Derive more directly instead of relying on the autoconf
-  // generated variable.
+  // FIXME: Derive directly instead of relying on the autoconf generated
+  // variable.
 
-  std::string Triple = LLVM_HOSTTRIPLE;
+  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]) &&