Index: lldb/trunk/include/lldb/Host/HostInfoBase.h
===================================================================
--- lldb/trunk/include/lldb/Host/HostInfoBase.h
+++ lldb/trunk/include/lldb/Host/HostInfoBase.h
@@ -61,6 +61,8 @@
   static const ArchSpec &
   GetArchitecture(ArchitectureKind arch_kind = eArchKindDefault);
 
+  static llvm::Optional<ArchitectureKind> ParseArchitectureKind(llvm::StringRef kind);
+
   //------------------------------------------------------------------
   /// Find a resource files that are related to LLDB.
   ///
Index: lldb/trunk/source/Core/ArchSpec.cpp
===================================================================
--- lldb/trunk/source/Core/ArchSpec.cpp
+++ lldb/trunk/source/Core/ArchSpec.cpp
@@ -9,7 +9,6 @@
 
 #include "lldb/Core/ArchSpec.h"
 
-#include "lldb/Host/HostInfo.h"
 #include "lldb/Utility/NameMatches.h"
 #include "lldb/Utility/Stream.h" // for Stream
 #include "lldb/Utility/StringList.h"
@@ -874,17 +873,7 @@
   if (ParseMachCPUDashSubtypeTriple(triple, *this))
     return true;
 
-  if (triple.startswith(LLDB_ARCH_DEFAULT)) {
-    // Special case for the current host default architectures...
-    if (triple.equals(LLDB_ARCH_DEFAULT_32BIT))
-      *this = HostInfo::GetArchitecture(HostInfo::eArchKind32);
-    else if (triple.equals(LLDB_ARCH_DEFAULT_64BIT))
-      *this = HostInfo::GetArchitecture(HostInfo::eArchKind64);
-    else if (triple.equals(LLDB_ARCH_DEFAULT))
-      *this = HostInfo::GetArchitecture(HostInfo::eArchKindDefault);
-  } else {
-    SetTriple(llvm::Triple(llvm::Triple::normalize(triple)));
-  }
+  SetTriple(llvm::Triple(llvm::Triple::normalize(triple)));
   return IsValid();
 }
 
Index: lldb/trunk/source/Host/common/HostInfoBase.cpp
===================================================================
--- lldb/trunk/source/Host/common/HostInfoBase.cpp
+++ lldb/trunk/source/Host/common/HostInfoBase.cpp
@@ -103,6 +103,14 @@
                                               : g_fields->m_host_arch_32;
 }
 
+llvm::Optional<HostInfoBase::ArchitectureKind> HostInfoBase::ParseArchitectureKind(llvm::StringRef kind) {
+  return llvm::StringSwitch<llvm::Optional<ArchitectureKind>>(kind)
+      .Case(LLDB_ARCH_DEFAULT, eArchKindDefault)
+      .Case(LLDB_ARCH_DEFAULT_32BIT, eArchKind32)
+      .Case(LLDB_ARCH_DEFAULT_64BIT, eArchKind64)
+      .Default(llvm::None);
+}
+
 bool HostInfoBase::GetLLDBPath(lldb::PathType type, FileSpec &file_spec) {
   file_spec.Clear();
 
@@ -258,6 +266,9 @@
   if (!ArchSpec::ContainsOnlyArch(normalized_triple))
     return ArchSpec(triple);
 
+  if (auto kind = HostInfo::ParseArchitectureKind(triple))
+    return HostInfo::GetArchitecture(*kind);
+
   llvm::Triple host_triple(llvm::sys::getDefaultTargetTriple());
 
   if (normalized_triple.getVendorName().empty())
Index: lldb/trunk/source/Target/Platform.cpp
===================================================================
--- lldb/trunk/source/Target/Platform.cpp
+++ lldb/trunk/source/Target/Platform.cpp
@@ -976,6 +976,9 @@
   if (!ArchSpec::ContainsOnlyArch(normalized_triple))
     return ArchSpec(triple);
 
+  if (auto kind = HostInfo::ParseArchitectureKind(triple))
+    return HostInfo::GetArchitecture(*kind);
+
   ArchSpec compatible_arch;
   ArchSpec raw_arch(triple);
   if (!IsCompatibleArchitecture(raw_arch, false, &compatible_arch))
Index: lldb/trunk/unittests/Host/HostInfoTest.cpp
===================================================================
--- lldb/trunk/unittests/Host/HostInfoTest.cpp
+++ lldb/trunk/unittests/Host/HostInfoTest.cpp
@@ -1,4 +1,4 @@
-//===-- HostTest.cpp --------------------------------------------*- C++ -*-===//
+//===-- HostInfoTest.cpp ----------------------------------------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "lldb/Host/HostInfo.h"
+#include "lldb/lldb-defines.h"
 #include "gtest/gtest.h"
 
 using namespace lldb_private;
@@ -37,4 +38,8 @@
   EXPECT_EQ(spec.GetTriple().getOS(), triple.getOS());
   EXPECT_EQ(spec.GetTriple().getVendor(), triple.getVendor());
   EXPECT_EQ(spec.GetTriple().getEnvironment(), triple.getEnvironment());
+
+  // Test LLDB_ARCH_DEFAULT
+  EXPECT_EQ(HostInfo::GetAugmentedArchSpec(LLDB_ARCH_DEFAULT).GetTriple(),
+            HostInfo::GetArchitecture(HostInfo::eArchKindDefault).GetTriple());
 }