[clang-cl] Support the /Ob3 flag

According to the docs, this was added in VS2019 and specifies more
aggressive inlining than /Ob2. Let's treat it the same as /Ob2 for now.

Author: zmodem

clang/docs/UsersManual.rst

@@ -4632,6 +4632,7 @@ Execute ``clang-cl /?`` to see a list of supported options:
       /Ob0                    Disable function inlining
       /Ob1                    Only inline functions which are (explicitly or implicitly) marked inline
       /Ob2                    Inline functions as deemed beneficial by the compiler
+      /Ob3                    Same as /Ob2
       /Od                     Disable optimization
       /Og                     No effect
       /Oi-                    Disable use of builtin functions

clang/include/clang/Driver/Options.td

@@ -8262,6 +8262,8 @@ def : CLFlag<"Ob1">, Alias<_SLASH_O>, AliasArgs<["b1"]>,
   HelpText<"Only inline functions explicitly or implicitly marked inline">;
 def : CLFlag<"Ob2">, Alias<_SLASH_O>, AliasArgs<["b2"]>,
   HelpText<"Inline functions as deemed beneficial by the compiler">;
+def : CLFlag<"Ob3">, Alias<_SLASH_O>, AliasArgs<["b3"]>,
+  HelpText<"Same as /Ob2">;
 def : CLFlag<"Od", [CLOption, DXCOption]>, Alias<_SLASH_O>, AliasArgs<["d"]>,
   HelpText<"Disable optimization">;
 def : CLFlag<"Og">, Alias<_SLASH_O>, AliasArgs<["g"]>,

clang/lib/Driver/ToolChains/MSVC.cpp

@@ -880,6 +880,7 @@ static void TranslateOptArg(Arg *A, llvm::opt::DerivedArgList &DAL,
           DAL.AddFlagArg(A, Opts.getOption(options::OPT_finline_hint_functions));
           break;
         case '2':
+        case '3':
           DAL.AddFlagArg(A, Opts.getOption(options::OPT_finline_functions));
           break;
         }

clang/test/Driver/cl-options.c

@@ -163,7 +163,9 @@
 // Ob0: -fno-inline
 
 // RUN: %clang_cl /Ob2 -### -- %s 2>&1 | FileCheck -check-prefix=Ob2 %s
+// RUN: %clang_cl /Ob3 -### -- %s 2>&1 | FileCheck -check-prefix=Ob2 %s
 // RUN: %clang_cl /Odb2 -### -- %s 2>&1 | FileCheck -check-prefix=Ob2 %s
+// RUN: %clang_cl /Odb3 -### -- %s 2>&1 | FileCheck -check-prefix=Ob2 %s
 // RUN: %clang_cl /O2 /Ob2 -### -- %s 2>&1 | FileCheck -check-prefix=Ob2 %s
 // Ob2-NOT: warning: argument unused during compilation: '/O2'
 // Ob2: -finline-functions