diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -509,4 +509,6 @@
   InGroup<DiagGroup<"stdlibcxx-not-found">>;
 
 def err_drv_cannot_mix_options : Error<"cannot specify '%1' along with '%0'">;
+
+def err_drv_invalid_object_mode : Error<"OBJECT_MODE setting %0 is not recognized and is not a valid setting.">;
 }
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -475,6 +475,26 @@
       Target.getOS() == llvm::Triple::Minix)
     return Target;
 
+  // On AIX, the env OBJECT_MODE may affect the resulting arch variant.
+  if (Target.isOSAIX()) {
+    if (Optional<std::string> ObjectModeValue =
+            llvm::sys::Process::GetEnv("OBJECT_MODE")) {
+      StringRef ObjectMode = *ObjectModeValue;
+      llvm::Triple::ArchType AT = llvm::Triple::UnknownArch;
+
+      if (ObjectMode.equals("64")) {
+        AT = Target.get64BitArchVariant().getArch();
+      } else if (ObjectMode.equals("32")) {
+        AT = Target.get32BitArchVariant().getArch();
+      } else {
+        D.Diag(diag::err_drv_invalid_object_mode) << ObjectMode;
+      }
+
+      if (AT != llvm::Triple::UnknownArch && AT != Target.getArch())
+        Target.setArch(AT);
+    }
+  }
+
   // Handle pseudo-target flags '-m64', '-mx32', '-m32' and '-m16'.
   Arg *A = Args.getLastArg(options::OPT_m64, options::OPT_mx32,
                            options::OPT_m32, options::OPT_m16);
diff --git a/clang/test/Driver/aix-object-mode.c b/clang/test/Driver/aix-object-mode.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Driver/aix-object-mode.c
@@ -0,0 +1,22 @@
+// Check that setting an OBJECT_MODE converts the AIX triple to the right variant.
+// RUN: env OBJECT_MODE=64 \
+// RUN: %clang -target powerpc-ibm-aix -print-target-triple | FileCheck -check-prefix=CHECK64 %s
+
+// RUN: env OBJECT_MODE=32 \
+// RUN: %clang -target powerpc64-ibm-aix -print-target-triple | FileCheck -check-prefix=CHECK32 %s
+
+// Command-line options win.
+// RUN: env OBJECT_MODE=64 \
+// RUN: %clang -target powerpc64-ibm-aix -print-target-triple -m32 | FileCheck -check-prefix=CHECK32 %s
+
+// RUN: env OBJECT_MODE=32 \
+// RUN: %clang -target powerpc-ibm-aix -print-target-triple -m64 | FileCheck -check-prefix=CHECK64 %s
+
+// CHECK32: powerpc-ibm-aix
+// CHECK64: powerpc64-ibm-aix
+
+// Emit a diagnostic if there is an invalid mode.
+// RUN: env OBJECT_MODE=31 \
+// RUN: not %clang -target powerpc-ibm-aix 2>&1 | FileCheck -check-prefix=DIAG %s
+
+// DIAG: error: OBJECT_MODE setting 31 is not recognized and is not a valid setting.