[X86] Add a /tune: option for clang-cl

[craig.topper]

Summary

We recently added support for -mtune. This patch adds /tune: so we can specify the tune CPU from clang-cl. MSVC doesn't support this but icc does.

[hans]

Would it be enough for users to specify /clang:-mtune instead? How does icc spell its option?

[craig.topper]

In D86820#2247336, @hans wrote:

Would it be enough for users to specify /clang:-mtune instead? How does icc spell its option?

I didn't know you could spell it as /clang:-mtune. ICC has /tune: according to this documentation https://software.intel.com/content/www/us/en/develop/documentation/cpp-compiler-developer-guide-and-reference/top/compiler-reference/compiler-options/compiler-option-details/code-generation-options/mtune-tune.html

[hans]

Okay, adding it to clang-cl seems fine to me. But I think it could be a simple alias?

clang/include/clang/Driver/Options.td

4707

Any reason this can't just be an alias?

[craig.topper]

Use an alias.

[hans]

lgtm

clang/include/clang/Driver/Options.td

def _SLASH_Zs : CLFlag<"Zs">, HelpText<"Syntax-check only">,
   Alias<fsyntax_only>;
 def _SLASH_openmp_ : CLFlag<"openmp-">,
   HelpText<"Disable OpenMP support">, Alias<fno_openmp>;
 def _SLASH_openmp : CLFlag<"openmp">, HelpText<"Enable OpenMP support">,
   Alias<fopenmp>;
 def _SLASH_openmp_experimental : CLFlag<"openmp:experimental">,
   HelpText<"Enable OpenMP support with experimental SIMD support">,
   Alias<fopenmp>;
+def _SLASH_tune : CLCompileJoined<"tune:">,
+  HelpText<"Set CPU for optimization without affecting instruction set">,
+  Alias<mtune_EQ>;
 
 // Non-aliases:
 
 def _SLASH_arch : CLCompileJoined<"arch:">,
   HelpText<"Set architecture for code generation">;
 
 def _SLASH_M_Group : OptionGroup<"</M group>">, Group<cl_compile_Group>;
 def _SLASH_volatile_Group : OptionGroup<"</volatile group>">,
   Group<cl_compile_Group>;
 
 def _SLASH_EH : CLJoined<"EH">, HelpText<"Set exception handling model">;
 def _SLASH_EP : CLFlag<"EP">,
   HelpText<"Disable linemarker output and preprocess to stdout">;
 def _SLASH_FA : CLFlag<"FA">,

clang/test/Driver/cl-x86-flags.c

 #if _M_IX86_FP || !__AVX__ || !__AVX2__ || !__AVX512F__  || !__AVX512BW__
 #error fail
 #endif
 #endif
 
 // RUN: %clang_cl -m64 -arch:avx512 --target=i386-pc-windows -### -- 2>&1 %s | FileCheck -check-prefix=avx51264 %s
 // avx51264: argument unused during compilation
 
+// RUN: %clang_cl -m64 -arch:AVX -tune:haswell --target=x86_64-pc-windows -### -- 2>&1 %s | FileCheck -check-prefix=tune %s
+// tune: "-target-cpu" "sandybridge"
+// tune-SAME: "-tune-cpu" "haswell"
+
 void f() {
 }