diff --git a/llvm/lib/IR/LegacyPassManager.cpp b/llvm/lib/IR/LegacyPassManager.cpp
--- a/llvm/lib/IR/LegacyPassManager.cpp
+++ b/llvm/lib/IR/LegacyPassManager.cpp
@@ -52,15 +52,14 @@
 };
 } // namespace
 
-static cl::opt<enum PassDebugLevel>
-PassDebugging("debug-pass", cl::Hidden,
-                  cl::desc("Print PassManager debugging information"),
-                  cl::values(
-  clEnumVal(Disabled  , "disable debug output"),
-  clEnumVal(Arguments , "print pass arguments to pass to 'opt'"),
-  clEnumVal(Structure , "print pass structure before run()"),
-  clEnumVal(Executions, "print pass name before it is executed"),
-  clEnumVal(Details   , "print pass details when it is executed")));
+static cl::opt<enum PassDebugLevel> PassDebugging(
+    "debug-pass", cl::Hidden,
+    cl::desc("Print legacy PassManager debugging information"),
+    cl::values(clEnumVal(Disabled, "disable debug output"),
+               clEnumVal(Arguments, "print pass arguments to pass to 'opt'"),
+               clEnumVal(Structure, "print pass structure before run()"),
+               clEnumVal(Executions, "print pass name before it is executed"),
+               clEnumVal(Details, "print pass details when it is executed")));
 
 /// isPassDebuggingExecutionsOrMore - Return true if -debug-pass=Executions
 /// or higher is specified.
diff --git a/llvm/tools/opt/opt.cpp b/llvm/tools/opt/opt.cpp
--- a/llvm/tools/opt/opt.cpp
+++ b/llvm/tools/opt/opt.cpp
@@ -66,14 +66,15 @@
 
 // The OptimizationList is automatically populated with registered Passes by the
 // PassNameParser.
-//
-static cl::list<const PassInfo*, bool, PassNameParser>
-PassList(cl::desc("Optimizations available:"));
+static cl::list<const PassInfo *, bool, PassNameParser> PassList(cl::desc(
+    "Optimizations available (use '-passes=' for the new pass manager)"));
 
-static cl::opt<bool>
-    EnableNewPassManager("enable-new-pm",
-                         cl::desc("Enable the new pass manager"),
-                         cl::init(LLVM_ENABLE_NEW_PASS_MANAGER));
+static cl::opt<bool> EnableNewPassManager(
+    "enable-new-pm",
+    cl::desc("Enable the new pass manager, translating "
+             "'opt -foo' to 'opt -passes=foo'. This is strictly for the new PM "
+             "migration, use '-passes=' when possible."),
+    cl::init(LLVM_ENABLE_NEW_PASS_MANAGER));
 
 // This flag specifies a textual description of the optimization pass pipeline
 // to run over the module. This flag switches opt to use the new pass manager
@@ -84,8 +85,6 @@
     cl::desc("A textual description of the pass pipeline for optimizing"),
     cl::Hidden);
 
-// Other command line options...
-//
 static cl::opt<std::string>
 InputFilename(cl::Positional, cl::desc("<input bitcode file>"),
     cl::init("-"), cl::value_desc("filename"));
@@ -142,44 +141,46 @@
     StripNamedMetadata("strip-named-metadata",
                        cl::desc("Strip module-level named metadata"));
 
-static cl::opt<bool> DisableInline("disable-inlining",
-                                   cl::desc("Do not run the inliner pass"));
+static cl::opt<bool>
+    DisableInline("disable-inlining",
+                  cl::desc("Do not run the inliner pass (legacy PM only)"));
 
 static cl::opt<bool>
 DisableOptimizations("disable-opt",
                      cl::desc("Do not run any optimization passes"));
 
-static cl::opt<bool>
-StandardLinkOpts("std-link-opts",
-                 cl::desc("Include the standard link time optimizations"));
+static cl::opt<bool> StandardLinkOpts(
+    "std-link-opts",
+    cl::desc("Include the standard link time optimizations (legacy PM only)"));
 
 static cl::opt<bool>
-OptLevelO0("O0",
-  cl::desc("Optimization level 0. Similar to clang -O0"));
+    OptLevelO0("O0", cl::desc("Optimization level 0. Similar to clang -O0. "
+                              "Use -passes='default<O0>' for the new PM"));
 
 static cl::opt<bool>
-OptLevelO1("O1",
-           cl::desc("Optimization level 1. Similar to clang -O1"));
+    OptLevelO1("O1", cl::desc("Optimization level 1. Similar to clang -O1. "
+                              "Use -passes='default<O1>' for the new PM"));
 
 static cl::opt<bool>
-OptLevelO2("O2",
-           cl::desc("Optimization level 2. Similar to clang -O2"));
+    OptLevelO2("O2", cl::desc("Optimization level 2. Similar to clang -O2. "
+                              "Use -passes='default<O2>' for the new PM"));
 
 static cl::opt<bool>
-OptLevelOs("Os",
-           cl::desc("Like -O2 with extra optimizations for size. Similar to clang -Os"));
+    OptLevelOs("Os", cl::desc("Like -O2 but size-conscious. Similar to clang "
+                              "-Os. Use -passes='default<Os>' for the new PM"));
 
-static cl::opt<bool>
-OptLevelOz("Oz",
-           cl::desc("Like -Os but reduces code size further. Similar to clang -Oz"));
+static cl::opt<bool> OptLevelOz(
+    "Oz",
+    cl::desc("Like -O2 but optimize for code size above all else. Similar to "
+             "clang -Oz. Use -passes='default<Oz>' for the new PM"));
 
 static cl::opt<bool>
-OptLevelO3("O3",
-           cl::desc("Optimization level 3. Similar to clang -O3"));
+    OptLevelO3("O3", cl::desc("Optimization level 3. Similar to clang -O3. "
+                              "Use -passes='default<O3>' for the new PM"));
 
-static cl::opt<unsigned>
-CodeGenOptLevel("codegen-opt-level",
-                cl::desc("Override optimization level for codegen hooks"));
+static cl::opt<unsigned> CodeGenOptLevel(
+    "codegen-opt-level",
+    cl::desc("Override optimization level for codegen hooks, legacy PM only"));
 
 static cl::opt<std::string>
 TargetTriple("mtriple", cl::desc("Override target triple for module"));
@@ -205,7 +206,8 @@
                 cl::ZeroOrMore);
 
 static cl::opt<bool>
-AnalyzeOnly("analyze", cl::desc("Only perform analysis, no optimization"));
+    AnalyzeOnly("analyze", cl::desc("Only perform analysis, no optimization. "
+                                    "Legacy pass manager only."));
 
 static cl::opt<bool> EnableDebugify(
     "enable-debugify",
@@ -231,10 +233,10 @@
     cl::desc("Preserve use-list order when writing LLVM assembly."),
     cl::init(false), cl::Hidden);
 
-static cl::opt<bool>
-    RunTwice("run-twice",
-             cl::desc("Run all passes twice, re-using the same pass manager."),
-             cl::init(false), cl::Hidden);
+static cl::opt<bool> RunTwice("run-twice",
+                              cl::desc("Run all passes twice, re-using the "
+                                       "same pass manager (legacy PM only)."),
+                              cl::init(false), cl::Hidden);
 
 static cl::opt<bool> DiscardValueNames(
     "discard-value-names",