Index: include/lldb/Utility/ArchSpec.h
===================================================================
--- include/lldb/Utility/ArchSpec.h
+++ include/lldb/Utility/ArchSpec.h
@@ -377,19 +377,19 @@
   }
 
   bool TripleVendorIsUnspecifiedUnknown() const {
-    return m_triple.getVendor() == llvm::Triple::UnknownVendor &&
-           m_triple.getVendorName().empty();
+    return m_triple.getVendor() == llvm::Triple::UnknownVendor;
   }
 
   bool TripleOSWasSpecified() const { return !m_triple.getOSName().empty(); }
 
-  bool TripleEnvironmentWasSpecified() const {
-    return !m_triple.getEnvironmentName().empty();
+  bool TripleOSIsUnspecifiedUnknown() const {
+    return m_triple.getOS() == llvm::Triple::UnknownOS;
   }
 
-  bool TripleOSIsUnspecifiedUnknown() const {
-    return m_triple.getOS() == llvm::Triple::UnknownOS &&
-           m_triple.getOSName().empty();
+  bool TripleEnvironmentWasSpecified() const { return m_triple.hasEnvironment(); }
+
+  bool TripleEnvironmentIsUnspecifiedUnknown() const {
+    return m_triple.getEnvironment() == llvm::Triple::UnknownEnvironment;
   }
 
   //------------------------------------------------------------------
Index: source/Utility/ArchSpec.cpp
===================================================================
--- source/Utility/ArchSpec.cpp
+++ source/Utility/ArchSpec.cpp
@@ -903,10 +903,9 @@
     if (other.GetCore() != eCore_uknownMach64)
       UpdateCore();
   }
-  if (GetTriple().getEnvironment() == llvm::Triple::UnknownEnvironment &&
-      !TripleVendorWasSpecified()) {
-    if (other.TripleVendorWasSpecified())
-      GetTriple().setEnvironment(other.GetTriple().getEnvironment());
+  if (TripleEnvironmentIsUnspecifiedUnknown() &&
+      !other.TripleEnvironmentIsUnspecifiedUnknown()) {
+    GetTriple().setEnvironment(other.GetTriple().getEnvironment());
   }
   // If this and other are both arm ArchSpecs and this ArchSpec is a generic
   // "some kind of arm" spec but the other ArchSpec is a specific arm core,
Index: unittests/Utility/ArchSpecTest.cpp
===================================================================
--- unittests/Utility/ArchSpecTest.cpp
+++ unittests/Utility/ArchSpecTest.cpp
@@ -134,22 +134,46 @@
 }
 
 TEST(ArchSpecTest, MergeFrom) {
-  ArchSpec A;
-  ArchSpec B("x86_64-pc-linux");
-
-  EXPECT_FALSE(A.IsValid());
-  ASSERT_TRUE(B.IsValid());
-  EXPECT_EQ(llvm::Triple::ArchType::x86_64, B.GetTriple().getArch());
-  EXPECT_EQ(llvm::Triple::VendorType::PC, B.GetTriple().getVendor());
-  EXPECT_EQ(llvm::Triple::OSType::Linux, B.GetTriple().getOS());
-  EXPECT_EQ(ArchSpec::eCore_x86_64_x86_64, B.GetCore());
-
-  A.MergeFrom(B);
-  ASSERT_TRUE(A.IsValid());
-  EXPECT_EQ(llvm::Triple::ArchType::x86_64, A.GetTriple().getArch());
-  EXPECT_EQ(llvm::Triple::VendorType::PC, A.GetTriple().getVendor());
-  EXPECT_EQ(llvm::Triple::OSType::Linux, A.GetTriple().getOS());
-  EXPECT_EQ(ArchSpec::eCore_x86_64_x86_64, A.GetCore());
+  {
+    ArchSpec A;
+    ArchSpec B("x86_64-pc-linux");
+
+    EXPECT_FALSE(A.IsValid());
+    ASSERT_TRUE(B.IsValid());
+    EXPECT_EQ(llvm::Triple::ArchType::x86_64, B.GetTriple().getArch());
+    EXPECT_EQ(llvm::Triple::VendorType::PC, B.GetTriple().getVendor());
+    EXPECT_EQ(llvm::Triple::OSType::Linux, B.GetTriple().getOS());
+    EXPECT_EQ(ArchSpec::eCore_x86_64_x86_64, B.GetCore());
+
+    A.MergeFrom(B);
+    ASSERT_TRUE(A.IsValid());
+    EXPECT_EQ(llvm::Triple::ArchType::x86_64, A.GetTriple().getArch());
+    EXPECT_EQ(llvm::Triple::VendorType::PC, A.GetTriple().getVendor());
+    EXPECT_EQ(llvm::Triple::OSType::Linux, A.GetTriple().getOS());
+    EXPECT_EQ(ArchSpec::eCore_x86_64_x86_64, A.GetCore());
+  }
+  {
+    ArchSpec A("aarch64-unknown-unknown-unknown");
+    ArchSpec B("aarch64-unknown-linux-android");
+
+    EXPECT_TRUE(A.IsValid());
+    EXPECT_TRUE(B.IsValid());
+
+    EXPECT_EQ(llvm::Triple::ArchType::aarch64, B.GetTriple().getArch());
+    EXPECT_EQ(llvm::Triple::VendorType::UnknownVendor,
+              B.GetTriple().getVendor());
+    EXPECT_EQ(llvm::Triple::OSType::Linux, B.GetTriple().getOS());
+    EXPECT_EQ(llvm::Triple::EnvironmentType::Android,
+              B.GetTriple().getEnvironment());
+
+    A.MergeFrom(B);
+    EXPECT_EQ(llvm::Triple::ArchType::aarch64, A.GetTriple().getArch());
+    EXPECT_EQ(llvm::Triple::VendorType::UnknownVendor,
+              A.GetTriple().getVendor());
+    EXPECT_EQ(llvm::Triple::OSType::Linux, A.GetTriple().getOS());
+    EXPECT_EQ(llvm::Triple::EnvironmentType::Android,
+              A.GetTriple().getEnvironment());
+  }
 }
 
 TEST(ArchSpecTest, MergeFromMachOUnknown) {
@@ -232,3 +256,58 @@
   EXPECT_FALSE(ArchSpec());
   EXPECT_TRUE(ArchSpec("x86_64-pc-linux"));
 }
+
+TEST(ArchSpecTest, TripleComponentsWereSpecified) {
+  {
+    ArchSpec A("x86-unknown-unknown");
+    ASSERT_FALSE(A.TripleVendorWasSpecified());
+    ASSERT_FALSE(A.TripleOSWasSpecified());
+    ASSERT_FALSE(A.TripleEnvironmentWasSpecified());
+
+    ASSERT_TRUE(A.TripleVendorIsUnspecifiedUnknown());
+    ASSERT_TRUE(A.TripleOSIsUnspecifiedUnknown());
+    ASSERT_TRUE(A.TripleEnvironmentIsUnspecifiedUnknown());
+  }
+  {
+    ArchSpec A("arm-pc-linux-android");
+    ASSERT_TRUE(A.TripleVendorWasSpecified());
+    ASSERT_TRUE(A.TripleOSWasSpecified());
+    ASSERT_TRUE(A.TripleEnvironmentWasSpecified());
+
+    ASSERT_FALSE(A.TripleVendorIsUnspecifiedUnknown());
+    ASSERT_FALSE(A.TripleOSIsUnspecifiedUnknown());
+    ASSERT_FALSE(A.TripleEnvironmentIsUnspecifiedUnknown());
+  }
+  {
+    ArchSpec A("aarch64-unknown-linux-android");
+    ASSERT_TRUE(A.TripleVendorWasSpecified());
+    ASSERT_TRUE(A.TripleOSWasSpecified());
+    ASSERT_TRUE(A.TripleEnvironmentWasSpecified());
+
+    ASSERT_TRUE(A.TripleVendorIsUnspecifiedUnknown());
+    ASSERT_FALSE(A.TripleOSIsUnspecifiedUnknown());
+    ASSERT_FALSE(A.TripleEnvironmentIsUnspecifiedUnknown());
+  }
+  {
+    ArchSpec A("");
+    ASSERT_FALSE(A.TripleVendorWasSpecified());
+    ASSERT_FALSE(A.TripleOSWasSpecified());
+    ASSERT_FALSE(A.TripleEnvironmentWasSpecified());
+
+    ASSERT_TRUE(A.TripleVendorIsUnspecifiedUnknown());
+    ASSERT_TRUE(A.TripleOSIsUnspecifiedUnknown());
+    ASSERT_TRUE(A.TripleEnvironmentIsUnspecifiedUnknown());
+  }
+  {
+    ArchSpec A("arm---");
+    // Note: llvm::Triple::normalize interprets empty-string as "unknown"
+    // instead of unspecified.
+    ASSERT_TRUE(A.TripleVendorWasSpecified());
+    ASSERT_TRUE(A.TripleOSWasSpecified());
+    ASSERT_TRUE(A.TripleEnvironmentWasSpecified());
+
+    ASSERT_TRUE(A.TripleVendorIsUnspecifiedUnknown());
+    ASSERT_TRUE(A.TripleOSIsUnspecifiedUnknown());
+    ASSERT_TRUE(A.TripleEnvironmentIsUnspecifiedUnknown());
+  }
+}