Index: test/tools/llvm-nm/X86/posix-aliases.test
===================================================================
--- test/tools/llvm-nm/X86/posix-aliases.test
+++ test/tools/llvm-nm/X86/posix-aliases.test
@@ -0,0 +1,5 @@
+# RUN: llvm-nm -P %p/Inputs/hello.obj.elf-x86_64 > %t1
+# RUN: llvm-nm -format=posix %p/Inputs/hello.obj.elf-x86_64 > %t2
+# RUN: llvm-nm -portability %p/Inputs/hello.obj.elf-x86_64 > %t3
+# RUN: diff %t1 %t2
+# RUN: diff %t1 %t3
Index: tools/llvm-nm/llvm-nm.cpp
===================================================================
--- tools/llvm-nm/llvm-nm.cpp
+++ tools/llvm-nm/llvm-nm.cpp
@@ -91,6 +91,8 @@
                         cl::Grouping);
 cl::opt<bool> POSIXFormat("P", cl::desc("Alias for --format=posix"),
                           cl::Grouping);
+cl::alias Portability("portability", cl::desc("Alias for --format=posix"),
+                      cl::aliasopt(POSIXFormat), cl::NotHidden);
 cl::opt<bool> DarwinFormat("m", cl::desc("Alias for --format=darwin"),
                            cl::Grouping);