r337552 - Implement cpu_dispatch/cpu_specific Multiversioning

Keane, Erich via cfe-commits cfe-commits at lists.llvm.org
Mon Sep 10 06:46:53 PDT 2018


Oooh, good catch, thanks Richard!  I suspect that lambdas should be prohibited.  I commit a patch to do that later today.

For target_clones, it seems like it should make sense to allow lambdas, so I’ll validate that as well.  For ‘target’, it doesn’t seem possible to spell a multiversioned version anyway (other than “default”, but we don’t seem to attempt a resolver there anyway).

There is no compatibility issues with prohibiting it, since ICC’s response to your code sample is:

<source>(1): internal error: bad pointer
  auto x = []() __attribute__((cpu_dispatch(atom))) {};

Anyway, I’ll fix this right away, thanks again!
-Erich



From: Richard Smith [mailto:richard at metafoo.co.uk]
Sent: Friday, September 7, 2018 2:44 PM
To: Keane, Erich <erich.keane at intel.com>
Cc: cfe-commits <cfe-commits at lists.llvm.org>
Subject: Re: r337552 - Implement cpu_dispatch/cpu_specific Multiversioning

(Noticed while reviewing https://reviews.llvm.org/D51812)

Should these attributes be disallowed on lambdas? Currently we allow them, but that seems questionable since the call operator of a lambda can't be overloaded. Eg:

auto x = []() __attribute__((cpu_dispatch(atom))) {};
void f() { x(); }

... generates an ifuc calling a resolver that can never be defined (and likewise for cpu_specific).

On Fri, 20 Jul 2018 at 07:18, Erich Keane via cfe-commits <cfe-commits at lists.llvm.org<mailto:cfe-commits at lists.llvm.org>> wrote:
Author: erichkeane
Date: Fri Jul 20 07:13:28 2018
New Revision: 337552

URL: http://llvm.org/viewvc/llvm-project?rev=337552&view=rev
Log:
Implement cpu_dispatch/cpu_specific Multiversioning

As documented here: https://software.intel.com/en-us/node/682969 and
https://software.intel.com/en-us/node/523346. cpu_dispatch multiversioning
is an ICC feature that provides for function multiversioning.

This feature is implemented with two attributes: First, cpu_specific,
which specifies the individual function versions. Second, cpu_dispatch,
which specifies the location of the resolver function and the list of
resolvable functions.

This is valuable since it provides a mechanism where the resolver's TU
can be specified in one location, and the individual implementions
each in their own translation units.

The goal of this patch is to be source-compatible with ICC, so this
implementation diverges from the ICC implementation in a few ways:
1- Linux x86/64 only: This implementation uses ifuncs in order to
properly dispatch functions. This is is a valuable performance benefit
over the ICC implementation. A future patch will be provided to enable
this feature on Windows, but it will obviously more closely fit ICC's
implementation.
2- CPU Identification functions: ICC uses a set of custom functions to identify
the feature list of the host processor. This patch uses the cpu_supports
functionality in order to better align with 'target' multiversioning.
1- cpu_dispatch function def/decl: ICC's cpu_dispatch requires that the function
marked cpu_dispatch be an empty definition. This patch supports that as well,
however declarations are also permitted, since the linker will solve the
issue of multiple emissions.

Differential Revision: https://reviews.llvm.org/D47474

Added:
    cfe/trunk/test/CodeGen/attr-cpuspecific.c
    cfe/trunk/test/Sema/attr-cpuspecific.c
    cfe/trunk/test/SemaCXX/attr-cpuspecific.cpp
Modified:
    cfe/trunk/include/clang/AST/Decl.h
    cfe/trunk/include/clang/Basic/Attr.td
    cfe/trunk/include/clang/Basic/AttrDocs.td
    cfe/trunk/include/clang/Basic/DiagnosticGroups.td
    cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
    cfe/trunk/include/clang/Basic/TargetInfo.h
    cfe/trunk/include/clang/Basic/X86Target.def
    cfe/trunk/lib/AST/Decl.cpp
    cfe/trunk/lib/Basic/Targets/X86.cpp
    cfe/trunk/lib/Basic/Targets/X86.h
    cfe/trunk/lib/CodeGen/CGBuiltin.cpp
    cfe/trunk/lib/CodeGen/CodeGenFunction.cpp
    cfe/trunk/lib/CodeGen/CodeGenFunction.h
    cfe/trunk/lib/CodeGen/CodeGenModule.cpp
    cfe/trunk/lib/CodeGen/CodeGenModule.h
    cfe/trunk/lib/Parse/ParseDecl.cpp
    cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp
    cfe/trunk/lib/Sema/Sema.cpp
    cfe/trunk/lib/Sema/SemaDecl.cpp
    cfe/trunk/lib/Sema/SemaDeclAttr.cpp
    cfe/trunk/lib/Sema/SemaExpr.cpp
    cfe/trunk/lib/Sema/SemaOverload.cpp
    cfe/trunk/test/Misc/pragma-attribute-supported-attributes-list.test
    cfe/trunk/utils/TableGen/ClangAttrEmitter.cpp

Modified: cfe/trunk/include/clang/AST/Decl.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/AST/Decl.h?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/include/clang/AST/Decl.h (original)
+++ cfe/trunk/include/clang/AST/Decl.h Fri Jul 20 07:13:28 2018
@@ -2209,6 +2209,13 @@ public:
     getCanonicalDecl()->IsMultiVersion = V;
   }

+  /// True if this function is a multiversioned dispatch function as a part of
+  /// the cpu_specific/cpu_dispatch functionality.
+  bool isCPUDispatchMultiVersion() const;
+  /// True if this function is a multiversioned processor specific function as a
+  /// part of the cpu_specific/cpu_dispatch functionality.
+  bool isCPUSpecificMultiVersion() const;
+
   void setPreviousDeclaration(FunctionDecl * PrevDecl);

   FunctionDecl *getCanonicalDecl() override;

Modified: cfe/trunk/include/clang/Basic/Attr.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/Attr.td?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/Attr.td (original)
+++ cfe/trunk/include/clang/Basic/Attr.td Fri Jul 20 07:13:28 2018
@@ -168,6 +168,7 @@ class UnsignedArgument<string name, bit
 class VariadicUnsignedArgument<string name> : Argument<name, 1>;
 class VariadicExprArgument<string name> : Argument<name, 1>;
 class VariadicStringArgument<string name> : Argument<name, 1>;
+class VariadicIdentifierArgument<string name> : Argument<name, 1>;

 // Like VariadicUnsignedArgument except values are ParamIdx.
 class VariadicParamIdxArgument<string name> : Argument<name, 1>;
@@ -845,6 +846,27 @@ def Constructor : InheritableAttr {
   let Documentation = [Undocumented];
 }

+def CPUSpecific : InheritableAttr {
+  let Spellings = [Clang<"cpu_specific">];
+  let Args = [VariadicIdentifierArgument<"Cpus">];
+  let Subjects = SubjectList<[Function]>;
+  let Documentation = [CPUSpecificCPUDispatchDocs];
+  let AdditionalMembers = [{
+    unsigned ActiveArgIndex = 0;
+
+    IdentifierInfo *getCurCPUName() const {
+      return *(cpus_begin() + ActiveArgIndex);
+    }
+  }];
+}
+
+def CPUDispatch : InheritableAttr {
+  let Spellings = [Clang<"cpu_dispatch">];
+  let Args = [VariadicIdentifierArgument<"Cpus">];
+  let Subjects = SubjectList<[Function]>;
+  let Documentation = [CPUSpecificCPUDispatchDocs];
+}
+
 // CUDA attributes are spelled __attribute__((attr)) or __declspec(__attr__),
 // and they do not receive a [[]] spelling.
 def CUDAConstant : InheritableAttr {

Modified: cfe/trunk/include/clang/Basic/AttrDocs.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/AttrDocs.td?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/AttrDocs.td (original)
+++ cfe/trunk/include/clang/Basic/AttrDocs.td Fri Jul 20 07:13:28 2018
@@ -191,6 +191,65 @@ in generation of more efficient code.
   }];
 }

+def CPUSpecificCPUDispatchDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+The ``cpu_specific`` and ``cpu_dispatch`` attributes are used to define and
+resolve multiversioned functions. This form of multiversioning provides a
+mechanism for declaring versions across translation units and manually
+specifying the resolved function list. A specified CPU defines a set of minimum
+features that are required for the function to be called. The result of this is
+that future processors execute the most restrictive version of the function the
+new processor can execute.
+
+Function versions are defined with ``cpu_specific``, which takes one or more CPU
+names as a parameter. For example:
+
+.. code-block:: c
+
+  // Declares and defines the ivybridge version of single_cpu.
+  __attribute__((cpu_specific(ivybridge)))
+  void single_cpu(void){}
+
+  // Declares and defines the atom version of single_cpu.
+  __attribute__((cpu_specific(atom)))
+  void single_cpu(void){}
+
+  // Declares and defines both the ivybridge and atom version of multi_cpu.
+  __attribute__((cpu_specific(ivybridge, atom)))
+  void multi_cpu(void){}
+
+A dispatching (or resolving) function can be declared anywhere in a project's
+source code with ``cpu_dispatch``. This attribute takes one or more CPU names
+as a parameter (like ``cpu_specific``). Functions marked with ``cpu_dispatch``
+are not expected to be defined, only declared. If such a marked function has a
+definition, any side effects of the function are ignored; trivial function
+bodies are permissible for ICC compatibility.
+
+.. code-block:: c
+
+  // Creates a resolver for single_cpu above.
+  __attribute__((cpu_dispatch(ivybridge, atom)))
+  void single_cpu(void){}
+
+  // Creates a resolver for multi_cpu, but adds a 3rd version defined in another
+  // translation unit.
+  __attribute__((cpu_dispatch(ivybridge, atom, sandybridge)))
+  void multi_cpu(void){}
+
+Note that it is possible to have a resolving function that dispatches based on
+more or fewer options than are present in the program. Specifying fewer will
+result in the omitted options not being considered during resolution. Specifying
+a version for resolution that isn't defined in the program will result in a
+linking failure.
+
+It is also possible to specify a CPU name of ``generic`` which will be resolved
+if the executing processor doesn't satisfy the features required in the CPU
+name. The behavior of a program executing on a processor that doesn't satisfy
+any option of a multiversioned function is undefined.
+  }];
+}
+
 def C11NoReturnDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{

Modified: cfe/trunk/include/clang/Basic/DiagnosticGroups.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticGroups.td?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticGroups.td (original)
+++ cfe/trunk/include/clang/Basic/DiagnosticGroups.td Fri Jul 20 07:13:28 2018
@@ -1022,3 +1022,7 @@ def SpirCompat : DiagGroup<"spir-compat"

 // Warning for the experimental-isel options.
 def ExperimentalISel : DiagGroup<"experimental-isel">;
+
+// A warning group specifically for warnings related to function
+// multiversioning.
+def FunctionMultiVersioning : DiagGroup<"function-multiversion">;

Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
+++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Fri Jul 20 07:13:28 2018
@@ -608,6 +608,8 @@ def err_builtin_redeclare : Error<"canno
 def err_arm_invalid_specialreg : Error<"invalid special register for builtin">;
 def err_invalid_cpu_supports : Error<"invalid cpu feature string for builtin">;
 def err_invalid_cpu_is : Error<"invalid cpu name for builtin">;
+def err_invalid_cpu_specific_dispatch_value : Error<
+"invalid option '%0' for %select{cpu_specific|cpu_dispatch}1">;
 def err_builtin_needs_feature : Error<"%0 needs target feature %1">;
 def err_function_needs_feature
     : Error<"always_inline function %1 requires target feature '%2', but would "
@@ -3788,8 +3790,8 @@ def err_ovl_no_viable_subscript :
 def err_ovl_no_oper :
     Error<"type %0 does not provide a %select{subscript|call}1 operator">;
 def err_ovl_unresolvable : Error<
-  "reference to overloaded function could not be resolved; "
-  "did you mean to call it%select{| with no arguments}0?">;
+  "reference to %select{overloaded|multiversioned}1 function could not be "
+  "resolved; did you mean to call it%select{| with no arguments}0?">;
 def err_bound_member_function : Error<
   "reference to non-static member function must be called"
   "%select{|; did you mean to call it with no arguments?}0">;
@@ -9355,9 +9357,9 @@ def warn_shadow_field :
   InGroup<ShadowField>, DefaultIgnore;
 def note_shadow_field : Note<"declared here">;

-def err_target_required_in_redecl : Error<
-  "function declaration is missing 'target' attribute in a multiversioned "
-  "function">;
+def err_multiversion_required_in_redecl : Error<
+  "function declaration is missing %select{'target'|'cpu_specific' or "
+  "'cpu_dispatch'}0 attribute in a multiversioned function">;
 def note_multiversioning_caused_here : Note<
   "function multiversioning caused by this declaration">;
 def err_multiversion_after_used : Error<
@@ -9371,20 +9373,33 @@ def err_multiversion_duplicate : Error<
 def err_multiversion_noproto : Error<
   "multiversioned function must have a prototype">;
 def err_multiversion_no_other_attrs : Error<
-  "attribute 'target' multiversioning cannot be combined with other "
-  "attributes">;
+  "attribute '%select{target|cpu_specific|cpu_dispatch}0' multiversioning cannot be combined"
+  " with other attributes">;
 def err_multiversion_diff : Error<
   "multiversioned function declaration has a different %select{calling convention"
   "|return type|constexpr specification|inline specification|storage class|"
   "linkage}0">;
 def err_multiversion_doesnt_support : Error<
-  "multiversioned functions do not yet support %select{function templates|"
-  "virtual functions|deduced return types|constructors|destructors|"
-  "deleted functions|defaulted functions}0">;
+  "attribute '%select{target|cpu_specific|cpu_dispatch}0' multiversioned functions do not "
+  "yet support %select{function templates|virtual functions|"
+  "deduced return types|constructors|destructors|deleted functions|"
+  "defaulted functions|constexpr functions}1">;
 def err_multiversion_not_allowed_on_main : Error<
   "'main' cannot be a multiversioned function">;
 def err_multiversion_not_supported : Error<
  "function multiversioning is not supported on the current target">;
+def err_multiversion_types_mixed : Error<
+  "multiversioning attributes cannot be combined">;
+def err_cpu_dispatch_mismatch : Error<
+ "'cpu_dispatch' function redeclared with different CPUs">;
+def err_cpu_specific_multiple_defs : Error<
+ "multiple 'cpu_specific' functions cannot specify the same CPU: %0">;
+def warn_multiversion_duplicate_entries : Warning<
+ "CPU list contains duplicate entries; attribute ignored">,
+  InGroup<FunctionMultiVersioning>;
+def warn_dispatch_body_ignored : Warning<
+  "body of cpu_dispatch function will be ignored">,
+  InGroup<FunctionMultiVersioning>;

 // three-way comparison operator diagnostics
 def err_implied_comparison_category_type_not_found : Error<

Modified: cfe/trunk/include/clang/Basic/TargetInfo.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/TargetInfo.h?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/TargetInfo.h (original)
+++ cfe/trunk/include/clang/Basic/TargetInfo.h Fri Jul 20 07:13:28 2018
@@ -1092,6 +1092,27 @@ public:
   // argument.
   virtual bool validateCpuIs(StringRef Name) const { return false; }

+  // Validate a cpu_dispatch/cpu_specific CPU option, which is a different list
+  // from cpu_is, since it checks via features rather than CPUs directly.
+  virtual bool validateCPUSpecificCPUDispatch(StringRef Name) const {
+    return false;
+  }
+
+  // Get the character to be added for mangling purposes for cpu_specific.
+  virtual char CPUSpecificManglingCharacter(StringRef Name) const {
+    llvm_unreachable(
+        "cpu_specific Multiversioning not implemented on this target");
+  }
+
+  // Get a list of the features that make up the CPU option for
+  // cpu_specific/cpu_dispatch so that it can be passed to llvm as optimization
+  // options.
+  virtual void getCPUSpecificCPUDispatchFeatures(
+      StringRef Name, llvm::SmallVectorImpl<StringRef> &Features) const {
+    llvm_unreachable(
+        "cpu_specific Multiversioning not implemented on this target");
+  }
+
   // Returns maximal number of args passed in registers.
   unsigned getRegParmMax() const {
     assert(RegParmMax < 7 && "RegParmMax value is larger than AST can handle");

Modified: cfe/trunk/include/clang/Basic/X86Target.def
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/X86Target.def?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/X86Target.def (original)
+++ cfe/trunk/include/clang/Basic/X86Target.def Fri Jul 20 07:13:28 2018
@@ -29,6 +29,14 @@
 #define FEATURE(ENUM)
 #endif

+#ifndef CPU_SPECIFIC
+#define CPU_SPECIFIC(NAME, MANGLING, FEATURES)
+#endif
+
+#ifndef CPU_SPECIFIC_ALIAS
+#define CPU_SPECIFIC_ALIAS(NEW_NAME, NAME)
+#endif
+
 #define PROC_64_BIT true
 #define PROC_32_BIT false

@@ -276,6 +284,45 @@ FEATURE(FEATURE_AVX5124VNNIW)
 FEATURE(FEATURE_AVX5124FMAPS)
 FEATURE(FEATURE_AVX512VPOPCNTDQ)

+
+// FIXME: When commented out features are supported in LLVM, enable them here.
+CPU_SPECIFIC("generic", 'A', "")
+CPU_SPECIFIC("pentium", 'B', "")
+CPU_SPECIFIC("pentium_pro", 'C', "+cmov")
+CPU_SPECIFIC("pentium_mmx", 'D', "+mmx")
+CPU_SPECIFIC("pentium_ii", 'E', "+cmov,+mmx")
+CPU_SPECIFIC("pentium_iii", 'H', "+cmov,+mmx,+sse")
+CPU_SPECIFIC("pentium_iii_no_xmm_regs", 'H',"+cmov,+sse")
+CPU_SPECIFIC("pentium_4", 'J', "+cmov,+mmx,+sse,+sse2")
+CPU_SPECIFIC("pentium_m", 'K', "+cmov,+mmx,+sse,+sse2")
+CPU_SPECIFIC("pentium_4_sse3", 'L', "+cmov,+mmx,+sse,+sse2,+sse3")
+CPU_SPECIFIC("core_2_duo_ssse3", 'M', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3")
+CPU_SPECIFIC("core_2_duo_sse4_1", 'N', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1")
+CPU_SPECIFIC("atom", 'O', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+movbe")
+CPU_SPECIFIC("atom_sse4_2", 'c', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+popcnt")
+CPU_SPECIFIC("core_i7_sse4_2", 'P', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+popcnt")
+CPU_SPECIFIC("core_aes_pclmulqdq", 'Q', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+popcnt")
+CPU_SPECIFIC("atom_sse4_2_movbe", 'd', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+movbe,+popcnt")
+CPU_SPECIFIC("goldmont", 'i', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+movbe,+popcnt")
+CPU_SPECIFIC("sandybridge", 'R', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+popcnt,+avx")
+CPU_SPECIFIC_ALIAS("core_2nd_gen_avx", "sandybridge")
+CPU_SPECIFIC("ivybridge", 'S', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+popcnt,+f16c,+avx")
+CPU_SPECIFIC_ALIAS("core_3rd_gen_avx", "ivybridge")
+CPU_SPECIFIC("haswell", 'V', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+movbe,+popcnt,+f16c,+avx,+fma,+bmi,+lzcnt,+avx2")
+CPU_SPECIFIC_ALIAS("core_4th_gen_avx", "haswell")
+CPU_SPECIFIC("core_4th_gen_avx_tsx", 'W', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+movbe,+popcnt,+f16c,+avx,+fma,+bmi,+lzcnt,+avx2")
+CPU_SPECIFIC("broadwell", 'X', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+movbe,+popcnt,+f16c,+avx,+fma,+bmi,+lzcnt,+avx2,+adx")
+CPU_SPECIFIC_ALIAS("core_5th_gen_avx", "broadwell")
+CPU_SPECIFIC("core_5th_gen_avx_tsx", 'Y', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+movbe,+popcnt,+f16c,+avx,+fma,+bmi,+lzcnt,+avx2,+adx")
+CPU_SPECIFIC("knl", 'Z', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+movbe,+popcnt,+f16c,+avx,+fma,+bmi,+lzcnt,+avx2,+avx512f,+adx,+avx512er,+avx512pf,+avx512cd")
+CPU_SPECIFIC_ALIAS("mic_avx512", "knl")
+CPU_SPECIFIC("skylake", 'b', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+movbe,+popcnt,+f16c,+avx,+fma,+bmi,+lzcnt,+avx2,+adx,+mpx")
+CPU_SPECIFIC( "skylake_avx512", 'a', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+movbe,+popcnt,+f16c,+avx,+fma,+bmi,+lzcnt,+avx2,+avx512dq,+avx512f,+adx,+avx512cd,+avx512bw,+avx512vl,+clwb")
+CPU_SPECIFIC("cannonlake", 'e', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+movbe,+popcnt,+f16c,+avx,+fma,+bmi,+lzcnt,+avx2,+avx512dq,+avx512f,+adx,+avx512ifma,+avx512cd,+avx512bw,+avx512vl,+avx512vbmi")
+CPU_SPECIFIC("knm", 'j', "+cmov,+mmx,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+movbe,+popcnt,+f16c,+avx,+fma,+bmi,+lzcnt,+avx2,+avx512f,+adx,+avx512er,+avx512pf,+avx512cd,+avx5124fmaps,+avx5124vnniw,+avx512vpopcntdq")
+
+#undef CPU_SPECIFIC_ALIAS
+#undef CPU_SPECIFIC
 #undef PROC_64_BIT
 #undef PROC_32_BIT
 #undef FEATURE

Modified: cfe/trunk/lib/AST/Decl.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/Decl.cpp?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/lib/AST/Decl.cpp (original)
+++ cfe/trunk/lib/AST/Decl.cpp Fri Jul 20 07:13:28 2018
@@ -2873,6 +2873,14 @@ bool FunctionDecl::isNoReturn() const {
   return false;
 }

+bool FunctionDecl::isCPUDispatchMultiVersion() const {
+  return isMultiVersion() && hasAttr<CPUDispatchAttr>();
+}
+
+bool FunctionDecl::isCPUSpecificMultiVersion() const {
+  return isMultiVersion() && hasAttr<CPUSpecificAttr>();
+}
+
 void
 FunctionDecl::setPreviousDeclaration(FunctionDecl *PrevDecl) {
   redeclarable_base::setPreviousDecl(PrevDecl);

Modified: cfe/trunk/lib/Basic/Targets/X86.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Basic/Targets/X86.cpp?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/lib/Basic/Targets/X86.cpp (original)
+++ cfe/trunk/lib/Basic/Targets/X86.cpp Fri Jul 20 07:13:28 2018
@@ -1484,6 +1484,38 @@ unsigned X86TargetInfo::multiVersionSort
   return getFeaturePriority(getFeature(Name)) << 1;
 }

+bool X86TargetInfo::validateCPUSpecificCPUDispatch(StringRef Name) const {
+  return llvm::StringSwitch<bool>(Name)
+#define CPU_SPECIFIC(NAME, MANGLING, FEATURES) .Case(NAME, true)
+#define CPU_SPECIFIC_ALIAS(NEW_NAME, NAME) .Case(NEW_NAME, true)
+#include "clang/Basic/X86Target.def"
+      .Default(false);
+}
+
+static StringRef CPUSpecificCPUDispatchNameDealias(StringRef Name) {
+  return llvm::StringSwitch<StringRef>(Name)
+#define CPU_SPECIFIC_ALIAS(NEW_NAME, NAME) .Case(NEW_NAME, NAME)
+#include "clang/Basic/X86Target.def"
+      .Default(Name);
+}
+
+char X86TargetInfo::CPUSpecificManglingCharacter(StringRef Name) const {
+  return llvm::StringSwitch<char>(CPUSpecificCPUDispatchNameDealias(Name))
+#define CPU_SPECIFIC(NAME, MANGLING, FEATURES) .Case(NAME, MANGLING)
+#include "clang/Basic/X86Target.def"
+      .Default(0);
+}
+
+void X86TargetInfo::getCPUSpecificCPUDispatchFeatures(
+    StringRef Name, llvm::SmallVectorImpl<StringRef> &Features) const {
+  StringRef WholeList =
+      llvm::StringSwitch<StringRef>(CPUSpecificCPUDispatchNameDealias(Name))
+#define CPU_SPECIFIC(NAME, MANGLING, FEATURES) .Case(NAME, FEATURES)
+#include "clang/Basic/X86Target.def"
+          .Default("");
+  WholeList.split(Features, ',', /*MaxSplit=*/-1, /*KeepEmpty=*/false);
+}
+
 std::string X86TargetInfo::getCPUKindCanonicalName(CPUKind Kind) const {
   switch (Kind) {
   case CK_Generic:

Modified: cfe/trunk/lib/Basic/Targets/X86.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Basic/Targets/X86.h?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/lib/Basic/Targets/X86.h (original)
+++ cfe/trunk/lib/Basic/Targets/X86.h Fri Jul 20 07:13:28 2018
@@ -150,6 +150,14 @@ public:

   bool validateCpuIs(StringRef Name) const override;

+  bool validateCPUSpecificCPUDispatch(StringRef Name) const override;
+
+  char CPUSpecificManglingCharacter(StringRef Name) const override;
+
+  void getCPUSpecificCPUDispatchFeatures(
+      StringRef Name,
+      llvm::SmallVectorImpl<StringRef> &Features) const override;
+
   bool validateAsmConstraint(const char *&Name,
                              TargetInfo::ConstraintInfo &info) const override;


Modified: cfe/trunk/lib/CodeGen/CGBuiltin.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGBuiltin.cpp?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGBuiltin.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGBuiltin.cpp Fri Jul 20 07:13:28 2018
@@ -8904,11 +8904,10 @@ Value *CodeGenFunction::EmitX86CpuSuppor
   return EmitX86CpuSupports(FeatureStr);
 }

-Value *CodeGenFunction::EmitX86CpuSupports(ArrayRef<StringRef> FeatureStrs) {
+uint32_t
+CodeGenFunction::GetX86CpuSupportsMask(ArrayRef<StringRef> FeatureStrs) {
   // Processor features and mapping to processor feature value.
-
   uint32_t FeaturesMask = 0;
-
   for (const StringRef &FeatureStr : FeatureStrs) {
     unsigned Feature =
         StringSwitch<unsigned>(FeatureStr)
@@ -8917,7 +8916,14 @@ Value *CodeGenFunction::EmitX86CpuSuppor
         ;
     FeaturesMask |= (1U << Feature);
   }
+  return FeaturesMask;
+}
+
+Value *CodeGenFunction::EmitX86CpuSupports(ArrayRef<StringRef> FeatureStrs) {
+  return EmitX86CpuSupports(GetX86CpuSupportsMask(FeatureStrs));
+}

+llvm::Value *CodeGenFunction::EmitX86CpuSupports(uint32_t FeaturesMask) {
   // Matching the struct layout from the compiler-rt/libgcc structure that is
   // filled in:
   // unsigned int __cpu_vendor;

Modified: cfe/trunk/lib/CodeGen/CodeGenFunction.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenFunction.cpp?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenFunction.cpp (original)
+++ cfe/trunk/lib/CodeGen/CodeGenFunction.cpp Fri Jul 20 07:13:28 2018
@@ -2323,7 +2323,8 @@ void CodeGenFunction::checkTargetFeature
           << TargetDecl->getDeclName()
           << CGM.getContext().BuiltinInfo.getRequiredFeatures(BuiltinID);

-  } else if (TargetDecl->hasAttr<TargetAttr>()) {
+  } else if (TargetDecl->hasAttr<TargetAttr>() ||
+             TargetDecl->hasAttr<CPUSpecificAttr>()) {
     // Get the required features for the callee.

     const TargetAttr *TD = TargetDecl->getAttr<TargetAttr>();
@@ -2358,8 +2359,8 @@ void CodeGenFunction::EmitSanitizerStatR
   CGM.getSanStats().create(IRB, SSK);
 }

-llvm::Value *
-CodeGenFunction::FormResolverCondition(const MultiVersionResolverOption &RO) {
+llvm::Value *CodeGenFunction::FormResolverCondition(
+    const TargetMultiVersionResolverOption &RO) {
   llvm::Value *TrueCondition = nullptr;
   if (!RO.ParsedAttribute.Architecture.empty())
     TrueCondition = EmitX86CpuIs(RO.ParsedAttribute.Architecture);
@@ -2377,8 +2378,9 @@ CodeGenFunction::FormResolverCondition(c
   return TrueCondition;
 }

-void CodeGenFunction::EmitMultiVersionResolver(
-    llvm::Function *Resolver, ArrayRef<MultiVersionResolverOption> Options) {
+void CodeGenFunction::EmitTargetMultiVersionResolver(
+    llvm::Function *Resolver,
+    ArrayRef<TargetMultiVersionResolverOption> Options) {
   assert((getContext().getTargetInfo().getTriple().getArch() ==
               llvm::Triple::x86 ||
           getContext().getTargetInfo().getTriple().getArch() ==
@@ -2391,7 +2393,7 @@ void CodeGenFunction::EmitMultiVersionRe
   EmitX86CpuInit();

   llvm::Function *DefaultFunc = nullptr;
-  for (const MultiVersionResolverOption &RO : Options) {
+  for (const TargetMultiVersionResolverOption &RO : Options) {
     Builder.SetInsertPoint(CurBlock);
     llvm::Value *TrueCondition = FormResolverCondition(RO);

@@ -2412,6 +2414,44 @@ void CodeGenFunction::EmitMultiVersionRe
   Builder.CreateRet(DefaultFunc);
 }

+void CodeGenFunction::EmitCPUDispatchMultiVersionResolver(
+    llvm::Function *Resolver,
+    ArrayRef<CPUDispatchMultiVersionResolverOption> Options) {
+  assert((getContext().getTargetInfo().getTriple().getArch() ==
+              llvm::Triple::x86 ||
+          getContext().getTargetInfo().getTriple().getArch() ==
+              llvm::Triple::x86_64) &&
+         "Only implemented for x86 targets");
+
+  // Main function's basic block.
+  llvm::BasicBlock *CurBlock = createBasicBlock("resolver_entry", Resolver);
+  Builder.SetInsertPoint(CurBlock);
+  EmitX86CpuInit();
+
+  for (const CPUDispatchMultiVersionResolverOption &RO : Options) {
+    Builder.SetInsertPoint(CurBlock);
+
+    // "generic" case should catch-all.
+    if (RO.FeatureMask == 0) {
+      Builder.CreateRet(RO.Function);
+      return;
+    }
+    llvm::BasicBlock *RetBlock = createBasicBlock("resolver_return", Resolver);
+    llvm::IRBuilder<> RetBuilder(RetBlock);
+    RetBuilder.CreateRet(RO.Function);
+    CurBlock = createBasicBlock("resolver_else", Resolver);
+    llvm::Value *TrueCondition = EmitX86CpuSupports(RO.FeatureMask);
+    Builder.CreateCondBr(TrueCondition, RetBlock, CurBlock);
+  }
+
+  Builder.SetInsertPoint(CurBlock);
+  llvm::CallInst *TrapCall = EmitTrapCall(llvm::Intrinsic::trap);
+  TrapCall->setDoesNotReturn();
+  TrapCall->setDoesNotThrow();
+  Builder.CreateUnreachable();
+  Builder.ClearInsertionPoint();
+}
+
 llvm::DebugLoc CodeGenFunction::SourceLocToDebugLoc(SourceLocation Location) {
   if (CGDebugInfo *DI = getDebugInfo())
     return DI->SourceLocToDebugLoc(Location);

Modified: cfe/trunk/lib/CodeGen/CodeGenFunction.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenFunction.h?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenFunction.h (original)
+++ cfe/trunk/lib/CodeGen/CodeGenFunction.h Fri Jul 20 07:13:28 2018
@@ -4113,12 +4113,13 @@ public:

   void EmitSanitizerStatReport(llvm::SanitizerStatKind SSK);

-  struct MultiVersionResolverOption {
+  struct TargetMultiVersionResolverOption {
     llvm::Function *Function;
     TargetAttr::ParsedTargetAttr ParsedAttribute;
     unsigned Priority;
-    MultiVersionResolverOption(const TargetInfo &TargInfo, llvm::Function *F,
-                               const clang::TargetAttr::ParsedTargetAttr &PT)
+    TargetMultiVersionResolverOption(
+        const TargetInfo &TargInfo, llvm::Function *F,
+        const clang::TargetAttr::ParsedTargetAttr &PT)
         : Function(F), ParsedAttribute(PT), Priority(0u) {
       for (StringRef Feat : PT.Features)
         Priority = std::max(Priority,
@@ -4129,12 +4130,30 @@ public:
                             TargInfo.multiVersionSortPriority(PT.Architecture));
     }

-    bool operator>(const MultiVersionResolverOption &Other) const {
+    bool operator>(const TargetMultiVersionResolverOption &Other) const {
       return Priority > Other.Priority;
     }
   };
-  void EmitMultiVersionResolver(llvm::Function *Resolver,
-                                ArrayRef<MultiVersionResolverOption> Options);
+  void EmitTargetMultiVersionResolver(
+      llvm::Function *Resolver,
+      ArrayRef<TargetMultiVersionResolverOption> Options);
+
+  struct CPUDispatchMultiVersionResolverOption {
+    llvm::Function *Function;
+    // Note: EmitX86CPUSupports only has 32 bits available, so we store the mask
+    // as 32 bits here.  When 64-bit support is added to __builtin_cpu_supports,
+    // this can be extended to 64 bits.
+    uint32_t FeatureMask;
+    CPUDispatchMultiVersionResolverOption(llvm::Function *F, uint64_t Mask)
+        : Function(F), FeatureMask(static_cast<uint32_t>(Mask)) {}
+    bool operator>(const CPUDispatchMultiVersionResolverOption &Other) const {
+      return FeatureMask > Other.FeatureMask;
+    }
+  };
+  void EmitCPUDispatchMultiVersionResolver(
+      llvm::Function *Resolver,
+      ArrayRef<CPUDispatchMultiVersionResolverOption> Options);
+  static uint32_t GetX86CpuSupportsMask(ArrayRef<StringRef> FeatureStrs);

 private:
   QualType getVarArgType(const Expr *Arg);
@@ -4151,8 +4170,10 @@ private:
   llvm::Value *EmitX86CpuIs(StringRef CPUStr);
   llvm::Value *EmitX86CpuSupports(const CallExpr *E);
   llvm::Value *EmitX86CpuSupports(ArrayRef<StringRef> FeatureStrs);
+  llvm::Value *EmitX86CpuSupports(uint32_t Mask);
   llvm::Value *EmitX86CpuInit();
-  llvm::Value *FormResolverCondition(const MultiVersionResolverOption &RO);
+  llvm::Value *
+  FormResolverCondition(const TargetMultiVersionResolverOption &RO);
 };

 /// Helper class with most of the code for saving a value for a

Modified: cfe/trunk/lib/CodeGen/CodeGenModule.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenModule.cpp?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenModule.cpp (original)
+++ cfe/trunk/lib/CodeGen/CodeGenModule.cpp Fri Jul 20 07:13:28 2018
@@ -861,22 +861,38 @@ void CodeGenModule::setTLSMode(llvm::Glo
   GV->setThreadLocalMode(TLM);
 }

+static std::string getCPUSpecificMangling(const CodeGenModule &CGM,
+                                          StringRef Name) {
+  const TargetInfo &Target = CGM.getTarget();
+  return (Twine('.') + Twine(Target.CPUSpecificManglingCharacter(Name))).str();
+}
+
+static void AppendCPUSpecificCPUDispatchMangling(const CodeGenModule &CGM,
+                                                 const CPUSpecificAttr *Attr,
+                                                 raw_ostream &Out) {
+  // cpu_specific gets the current name, dispatch gets the resolver.
+  if (Attr)
+    Out << getCPUSpecificMangling(CGM, Attr->getCurCPUName()->getName());
+  else
+    Out << ".resolver";
+}
+
 static void AppendTargetMangling(const CodeGenModule &CGM,
                                  const TargetAttr *Attr, raw_ostream &Out) {
   if (Attr->isDefaultVersion())
     return;

   Out << '.';
-  const auto &Target = CGM.getTarget();
+  const TargetInfo &Target = CGM.getTarget();
   TargetAttr::ParsedTargetAttr Info =
       Attr->parse([&Target](StringRef LHS, StringRef RHS) {
-                    // Multiversioning doesn't allow "no-${feature}", so we can
-                    // only have "+" prefixes here.
-                    assert(LHS.startswith("+") && RHS.startswith("+") &&
-                           "Features should always have a prefix.");
-                    return Target.multiVersionSortPriority(LHS.substr(1)) >
-                           Target.multiVersionSortPriority(RHS.substr(1));
-                  });
+        // Multiversioning doesn't allow "no-${feature}", so we can
+        // only have "+" prefixes here.
+        assert(LHS.startswith("+") && RHS.startswith("+") &&
+               "Features should always have a prefix.");
+        return Target.multiVersionSortPriority(LHS.substr(1)) >
+               Target.multiVersionSortPriority(RHS.substr(1));
+      });

   bool IsFirst = true;

@@ -895,7 +911,7 @@ static void AppendTargetMangling(const C

 static std::string getMangledNameImpl(const CodeGenModule &CGM, GlobalDecl GD,
                                       const NamedDecl *ND,
-                                      bool OmitTargetMangling = false) {
+                                      bool OmitMultiVersionMangling = false) {
   SmallString<256> Buffer;
   llvm::raw_svector_ostream Out(Buffer);
   MangleContext &MC = CGM.getCXXABI().getMangleContext();
@@ -922,8 +938,14 @@ static std::string getMangledNameImpl(co
   }

   if (const auto *FD = dyn_cast<FunctionDecl>(ND))
-    if (FD->isMultiVersion() && !OmitTargetMangling)
-      AppendTargetMangling(CGM, FD->getAttr<TargetAttr>(), Out);
+    if (FD->isMultiVersion() && !OmitMultiVersionMangling) {
+      if (FD->isCPUDispatchMultiVersion() || FD->isCPUSpecificMultiVersion())
+        AppendCPUSpecificCPUDispatchMangling(
+            CGM, FD->getAttr<CPUSpecificAttr>(), Out);
+      else
+        AppendTargetMangling(CGM, FD->getAttr<TargetAttr>(), Out);
+    }
+
   return Out.str();
 }

@@ -936,7 +958,7 @@ void CodeGenModule::UpdateMultiVersionNa
   // allows us to lookup the version that was emitted when this wasn't a
   // multiversion function.
   std::string NonTargetName =
-      getMangledNameImpl(*this, GD, FD, /*OmitTargetMangling=*/true);
+      getMangledNameImpl(*this, GD, FD, /*OmitMultiVersionMangling=*/true);
   GlobalDecl OtherGD;
   if (lookupRepresentativeDecl(NonTargetName, OtherGD)) {
     assert(OtherGD.getCanonicalDecl()
@@ -979,11 +1001,30 @@ StringRef CodeGenModule::getMangledName(
     }
   }

+  const auto *FD = dyn_cast<FunctionDecl>(GD.getDecl());
+  // Since CPUSpecific can require multiple emits per decl, store the manglings
+  // separately.
+  if (FD &&
+      (FD->isCPUDispatchMultiVersion() || FD->isCPUSpecificMultiVersion())) {
+    const auto *SD = FD->getAttr<CPUSpecificAttr>();
+
+    std::pair<GlobalDecl, unsigned> SpecCanonicalGD{
+        CanonicalGD,
+        SD ? SD->ActiveArgIndex : std::numeric_limits<unsigned>::max()};
+
+    auto FoundName = CPUSpecificMangledDeclNames.find(SpecCanonicalGD);
+    if (FoundName != CPUSpecificMangledDeclNames.end())
+      return FoundName->second;
+
+    auto Result = CPUSpecificManglings.insert(
+        std::make_pair(getMangledNameImpl(*this, GD, FD), SpecCanonicalGD));
+    return CPUSpecificMangledDeclNames[SpecCanonicalGD] = Result.first->first();
+  }
+
   auto FoundName = MangledDeclNames.find(CanonicalGD);
   if (FoundName != MangledDeclNames.end())
     return FoundName->second;

-
   // Keep the first result in the case of a mangling collision.
   const auto *ND = cast<NamedDecl>(GD.getDecl());
   auto Result =
@@ -1321,8 +1362,9 @@ bool CodeGenModule::GetCPUAndFeaturesAtt
   const auto *FD = dyn_cast_or_null<FunctionDecl>(D);
   FD = FD ? FD->getMostRecentDecl() : FD;
   const auto *TD = FD ? FD->getAttr<TargetAttr>() : nullptr;
+  const auto *SD = FD ? FD->getAttr<CPUSpecificAttr>() : nullptr;
   bool AddedAttr = false;
-  if (TD) {
+  if (TD || SD) {
     llvm::StringMap<bool> FeatureMap;
     getFunctionFeatureMap(FeatureMap, FD);

@@ -1334,10 +1376,12 @@ bool CodeGenModule::GetCPUAndFeaturesAtt
     // While we populated the feature map above, we still need to
     // get and parse the target attribute so we can get the cpu for
     // the function.
-    TargetAttr::ParsedTargetAttr ParsedAttr = TD->parse();
-    if (ParsedAttr.Architecture != "" &&
-        getTarget().isValidCPUName(ParsedAttr.Architecture))
-      TargetCPU = ParsedAttr.Architecture;
+    if (TD) {
+      TargetAttr::ParsedTargetAttr ParsedAttr = TD->parse();
+      if (ParsedAttr.Architecture != "" &&
+          getTarget().isValidCPUName(ParsedAttr.Architecture))
+        TargetCPU = ParsedAttr.Architecture;
+    }
   } else {
     // Otherwise just add the existing target cpu and target features to the
     // function.
@@ -2037,6 +2081,10 @@ void CodeGenModule::EmitGlobal(GlobalDec
   if (Global->hasAttr<IFuncAttr>())
     return emitIFuncDefinition(GD);

+  // If this is a cpu_dispatch multiversion function, emit the resolver.
+  if (Global->hasAttr<CPUDispatchAttr>())
+    return emitCPUDispatchDefinition(GD);
+
   // If this is CUDA, be selective about which declarations we emit.
   if (LangOpts.CUDA) {
     if (LangOpts.CUDAIsDevice) {
@@ -2355,7 +2403,7 @@ static void ReplaceUsesOfNonProtoTypeWit

 void CodeGenModule::emitMultiVersionFunctions() {
   for (GlobalDecl GD : MultiVersionFuncs) {
-    SmallVector<CodeGenFunction::MultiVersionResolverOption, 10> Options;
+    SmallVector<CodeGenFunction::TargetMultiVersionResolverOption, 10> Options;
     const FunctionDecl *FD = cast<FunctionDecl>(GD.getDecl());
     getContext().forEachMultiversionedFunctionVersion(
         FD, [this, &GD, &Options](const FunctionDecl *CurFD) {
@@ -2387,28 +2435,75 @@ void CodeGenModule::emitMultiVersionFunc
           getModule().getOrInsertComdat(ResolverFunc->getName()));
     std::stable_sort(
         Options.begin(), Options.end(),
-        std::greater<CodeGenFunction::MultiVersionResolverOption>());
+        std::greater<CodeGenFunction::TargetMultiVersionResolverOption>());
     CodeGenFunction CGF(*this);
-    CGF.EmitMultiVersionResolver(ResolverFunc, Options);
+    CGF.EmitTargetMultiVersionResolver(ResolverFunc, Options);
   }
 }

+void CodeGenModule::emitCPUDispatchDefinition(GlobalDecl GD) {
+  const auto *FD = cast<FunctionDecl>(GD.getDecl());
+  assert(FD && "Not a FunctionDecl?");
+  const auto *DD = FD->getAttr<CPUDispatchAttr>();
+  assert(DD && "Not a cpu_dispatch Function?");
+  llvm::Type *DeclTy = getTypes().ConvertTypeForMem(FD->getType());
+
+  StringRef ResolverName = getMangledName(GD);
+  llvm::Type *ResolverType = llvm::FunctionType::get(
+      llvm::PointerType::get(DeclTy,
+                             Context.getTargetAddressSpace(FD->getType())),
+      false);
+  auto *ResolverFunc = cast<llvm::Function>(
+      GetOrCreateLLVMFunction(ResolverName, ResolverType, GlobalDecl{},
+                              /*ForVTable=*/false));
+
+  SmallVector<CodeGenFunction::CPUDispatchMultiVersionResolverOption, 10>
+      Options;
+  const TargetInfo &Target = getTarget();
+  for (const IdentifierInfo *II : DD->cpus()) {
+    // Get the name of the target function so we can look it up/create it.
+    std::string MangledName = getMangledNameImpl(*this, GD, FD, true) +
+                              getCPUSpecificMangling(*this, II->getName());
+    llvm::Constant *Func = GetOrCreateLLVMFunction(
+        MangledName, DeclTy, GD, /*ForVTable=*/false, /*DontDefer=*/false,
+        /*IsThunk=*/false, llvm::AttributeList(), ForDefinition);
+    llvm::SmallVector<StringRef, 32> Features;
+    Target.getCPUSpecificCPUDispatchFeatures(II->getName(), Features);
+    llvm::transform(Features, Features.begin(),
+                    [](StringRef Str) { return Str.substr(1); });
+    Features.erase(std::remove_if(
+        Features.begin(), Features.end(), [&Target](StringRef Feat) {
+          return !Target.validateCpuSupports(Feat);
+        }), Features.end());
+    Options.emplace_back(cast<llvm::Function>(Func),
+                         CodeGenFunction::GetX86CpuSupportsMask(Features));
+  }
+
+  llvm::sort(
+      Options.begin(), Options.end(),
+      std::greater<CodeGenFunction::CPUDispatchMultiVersionResolverOption>());
+  CodeGenFunction CGF(*this);
+  CGF.EmitCPUDispatchMultiVersionResolver(ResolverFunc, Options);
+}
+
 /// If an ifunc for the specified mangled name is not in the module, create and
 /// return an llvm IFunc Function with the specified type.
 llvm::Constant *
 CodeGenModule::GetOrCreateMultiVersionIFunc(GlobalDecl GD, llvm::Type *DeclTy,
-                                            StringRef MangledName,
                                             const FunctionDecl *FD) {
-  std::string IFuncName = (MangledName + ".ifunc").str();
+  std::string MangledName =
+      getMangledNameImpl(*this, GD, FD, /*OmitMultiVersionMangling=*/true);
+  std::string IFuncName = MangledName + ".ifunc";
   if (llvm::GlobalValue *IFuncGV = GetGlobalValue(IFuncName))
     return IFuncGV;

   // Since this is the first time we've created this IFunc, make sure
   // that we put this multiversioned function into the list to be
-  // replaced later.
-  MultiVersionFuncs.push_back(GD);
+  // replaced later if necessary (target multiversioning only).
+  if (!FD->isCPUDispatchMultiVersion() && !FD->isCPUSpecificMultiVersion())
+    MultiVersionFuncs.push_back(GD);

-  std::string ResolverName = (MangledName + ".resolver").str();
+  std::string ResolverName = MangledName + ".resolver";
   llvm::Type *ResolverType = llvm::FunctionType::get(
       llvm::PointerType::get(DeclTy,
                              Context.getTargetAddressSpace(FD->getType())),
@@ -2455,10 +2550,12 @@ llvm::Constant *CodeGenModule::GetOrCrea
       addDeferredDeclToEmit(GDDef);
     }

-    if (FD->isMultiVersion() && FD->getAttr<TargetAttr>()->isDefaultVersion()) {
-      UpdateMultiVersionNames(GD, FD);
+    if (FD->isMultiVersion()) {
+      const auto *TA = FD->getAttr<TargetAttr>();
+      if (TA && TA->isDefaultVersion())
+        UpdateMultiVersionNames(GD, FD);
       if (!IsForDefinition)
-        return GetOrCreateMultiVersionIFunc(GD, Ty, MangledName, FD);
+        return GetOrCreateMultiVersionIFunc(GD, Ty, FD);
     }
   }

@@ -3727,6 +3824,15 @@ void CodeGenModule::EmitGlobalFunctionDe
     AddGlobalDtor(Fn, DA->getPriority());
   if (D->hasAttr<AnnotateAttr>())
     AddGlobalAnnotations(D, Fn);
+
+  if (D->isCPUSpecificMultiVersion()) {
+    auto *Spec = D->getAttr<CPUSpecificAttr>();
+    // If there is another specific version we need to emit, do so here.
+    if (Spec->ActiveArgIndex + 1 < Spec->cpus_size()) {
+      ++Spec->ActiveArgIndex;
+      EmitGlobalFunctionDefinition(GD, nullptr);
+    }
+  }
 }

 void CodeGenModule::EmitAliasDefinition(GlobalDecl GD) {
@@ -5107,6 +5213,12 @@ void CodeGenModule::getFunctionFeatureMa
     // the attribute.
     Target.initFeatureMap(FeatureMap, getDiags(), TargetCPU,
                           ParsedAttr.Features);
+  } else if (const auto *SD = FD->getAttr<CPUSpecificAttr>()) {
+    llvm::SmallVector<StringRef, 32> FeaturesTmp;
+    Target.getCPUSpecificCPUDispatchFeatures(SD->getCurCPUName()->getName(),
+                                             FeaturesTmp);
+    std::vector<std::string> Features(FeaturesTmp.begin(), FeaturesTmp.end());
+    Target.initFeatureMap(FeatureMap, getDiags(), TargetCPU, Features);
   } else {
     Target.initFeatureMap(FeatureMap, getDiags(), TargetCPU,
                           Target.getTargetOpts().Features);

Modified: cfe/trunk/lib/CodeGen/CodeGenModule.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenModule.h?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenModule.h (original)
+++ cfe/trunk/lib/CodeGen/CodeGenModule.h Fri Jul 20 07:13:28 2018
@@ -366,6 +366,13 @@ private:
   llvm::MapVector<GlobalDecl, StringRef> MangledDeclNames;
   llvm::StringMap<GlobalDecl, llvm::BumpPtrAllocator> Manglings;

+  // An ordered map of canonical GlobalDecls paired with the cpu-index for
+  // cpu-specific name manglings.
+  llvm::MapVector<std::pair<GlobalDecl, unsigned>, StringRef>
+      CPUSpecificMangledDeclNames;
+  llvm::StringMap<std::pair<GlobalDecl, unsigned>, llvm::BumpPtrAllocator>
+      CPUSpecificManglings;
+
   /// Global annotations.
   std::vector<llvm::Constant*> Annotations;

@@ -1283,7 +1290,6 @@ private:

   llvm::Constant *GetOrCreateMultiVersionIFunc(GlobalDecl GD,
                                                llvm::Type *DeclTy,
-                                               StringRef MangledName,
                                                const FunctionDecl *FD);
   void UpdateMultiVersionNames(GlobalDecl GD, const FunctionDecl *FD);

@@ -1307,6 +1313,7 @@ private:
   void EmitGlobalVarDefinition(const VarDecl *D, bool IsTentative = false);
   void EmitAliasDefinition(GlobalDecl GD);
   void emitIFuncDefinition(GlobalDecl GD);
+  void emitCPUDispatchDefinition(GlobalDecl GD);
   void EmitObjCPropertyImplementations(const ObjCImplementationDecl *D);
   void EmitObjCIvarInitializations(ObjCImplementationDecl *D);


Modified: cfe/trunk/lib/Parse/ParseDecl.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Parse/ParseDecl.cpp?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/lib/Parse/ParseDecl.cpp (original)
+++ cfe/trunk/lib/Parse/ParseDecl.cpp Fri Jul 20 07:13:28 2018
@@ -215,6 +215,15 @@ static bool attributeHasIdentifierArg(co
 #undef CLANG_ATTR_IDENTIFIER_ARG_LIST
 }

+/// Determine whether the given attribute has a variadic identifier argument.
+static bool attributeHasVariadicIdentifierArg(const IdentifierInfo &II) {
+#define CLANG_ATTR_VARIADIC_IDENTIFIER_ARG_LIST
+  return llvm::StringSwitch<bool>(normalizeAttrName(II.getName()))
+#include "clang/Parse/AttrParserStringSwitches.inc"
+           .Default(false);
+#undef CLANG_ATTR_VARIADIC_IDENTIFIER_ARG_LIST
+}
+
 /// Determine whether the given attribute parses a type argument.
 static bool attributeIsTypeArgAttr(const IdentifierInfo &II) {
 #define CLANG_ATTR_TYPE_ARG_LIST
@@ -282,7 +291,8 @@ unsigned Parser::ParseAttributeArgsCommo
   ArgsVector ArgExprs;
   if (Tok.is(tok::identifier)) {
     // If this attribute wants an 'identifier' argument, make it so.
-    bool IsIdentifierArg = attributeHasIdentifierArg(*AttrName);
+    bool IsIdentifierArg = attributeHasIdentifierArg(*AttrName) ||
+                           attributeHasVariadicIdentifierArg(*AttrName);
     ParsedAttr::Kind AttrKind =
         ParsedAttr::getKind(AttrName, ScopeName, Syntax);

@@ -305,19 +315,25 @@ unsigned Parser::ParseAttributeArgsCommo

     // Parse the non-empty comma-separated list of expressions.
     do {
-      bool Uneval = attributeParsedArgsUnevaluated(*AttrName);
-      EnterExpressionEvaluationContext Unevaluated(
-          Actions,
-          Uneval ? Sema::ExpressionEvaluationContext::Unevaluated
-                 : Sema::ExpressionEvaluationContext::ConstantEvaluated);
-
-      ExprResult ArgExpr(
-          Actions.CorrectDelayedTyposInExpr(ParseAssignmentExpression()));
-      if (ArgExpr.isInvalid()) {
-        SkipUntil(tok::r_paren, StopAtSemi);
-        return 0;
+      ExprResult ArgExpr;
+      if (Tok.is(tok::identifier) &&
+          attributeHasVariadicIdentifierArg(*AttrName)) {
+        ArgExprs.push_back(ParseIdentifierLoc());
+      } else {
+        bool Uneval = attributeParsedArgsUnevaluated(*AttrName);
+        EnterExpressionEvaluationContext Unevaluated(
+            Actions,
+            Uneval ? Sema::ExpressionEvaluationContext::Unevaluated
+                   : Sema::ExpressionEvaluationContext::ConstantEvaluated);
+
+        ExprResult ArgExpr(
+            Actions.CorrectDelayedTyposInExpr(ParseAssignmentExpression()));
+        if (ArgExpr.isInvalid()) {
+          SkipUntil(tok::r_paren, StopAtSemi);
+          return 0;
+        }
+        ArgExprs.push_back(ArgExpr.get());
       }
-      ArgExprs.push_back(ArgExpr.get());
       // Eat the comma, move to the next argument
     } while (TryConsumeToken(tok::comma));
   }

Modified: cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp (original)
+++ cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp Fri Jul 20 07:13:28 2018
@@ -658,6 +658,11 @@ static void CheckFallThroughForBody(Sema
     else
       S.Diag(Loc, DiagID);
   };
+
+  // cpu_dispatch functions permit empty function bodies for ICC compatibility.
+  if (D->getAsFunction() && D->getAsFunction()->isCPUDispatchMultiVersion())
+    return;
+
   // Either in a function body compound statement, or a function-try-block.
   switch (CheckFallThrough(AC)) {
     case UnknownFallThrough:

Modified: cfe/trunk/lib/Sema/Sema.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/Sema.cpp?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/Sema.cpp (original)
+++ cfe/trunk/lib/Sema/Sema.cpp Fri Jul 20 07:13:28 2018
@@ -1585,6 +1585,7 @@ bool Sema::tryExprAsCall(Expr &E, QualTy
   }

   bool Ambiguous = false;
+  bool IsMV = false;

   if (Overloads) {
     for (OverloadExpr::decls_iterator it = Overloads->decls_begin(),
@@ -1598,11 +1599,16 @@ bool Sema::tryExprAsCall(Expr &E, QualTy
       if (const FunctionDecl *OverloadDecl
             = dyn_cast<FunctionDecl>((*it)->getUnderlyingDecl())) {
         if (OverloadDecl->getMinRequiredArguments() == 0) {
-          if (!ZeroArgCallReturnTy.isNull() && !Ambiguous) {
+          if (!ZeroArgCallReturnTy.isNull() && !Ambiguous &&
+              (!IsMV || !(OverloadDecl->isCPUDispatchMultiVersion() ||
+                          OverloadDecl->isCPUSpecificMultiVersion()))) {
             ZeroArgCallReturnTy = QualType();
             Ambiguous = true;
-          } else
+          } else {
             ZeroArgCallReturnTy = OverloadDecl->getReturnType();
+            IsMV = OverloadDecl->isCPUDispatchMultiVersion() ||
+                   OverloadDecl->isCPUSpecificMultiVersion();
+          }
         }
       }
     }
@@ -1683,7 +1689,7 @@ static void noteOverloads(Sema &S, const
     NamedDecl *Fn = (*It)->getUnderlyingDecl();
     // Don't print overloads for non-default multiversioned functions.
     if (const auto *FD = Fn->getAsFunction()) {
-      if (FD->isMultiVersion() &&
+      if (FD->isMultiVersion() && FD->hasAttr<TargetAttr>() &&
           !FD->getAttr<TargetAttr>()->isDefaultVersion())
         continue;
     }
@@ -1725,6 +1731,21 @@ static bool IsCallableWithAppend(Expr *E
           !isa<CXXOperatorCallExpr>(E));
 }

+static bool IsCPUDispatchCPUSpecificMultiVersion(const Expr *E) {
+  if (const auto *UO = dyn_cast<UnaryOperator>(E))
+    E = UO->getSubExpr();
+
+  if (const auto *ULE = dyn_cast<UnresolvedLookupExpr>(E)) {
+    if (ULE->getNumDecls() == 0)
+      return false;
+
+    const NamedDecl *ND = *ULE->decls_begin();
+    if (const auto *FD = dyn_cast<FunctionDecl>(ND))
+      return FD->isCPUDispatchMultiVersion() || FD->isCPUSpecificMultiVersion();
+  }
+  return false;
+}
+
 bool Sema::tryToRecoverWithCall(ExprResult &E, const PartialDiagnostic &PD,
                                 bool ForceComplain,
                                 bool (*IsPlausibleResult)(QualType)) {
@@ -1741,12 +1762,13 @@ bool Sema::tryToRecoverWithCall(ExprResu
     // so we can emit a fixit and carry on pretending that E was
     // actually a CallExpr.
     SourceLocation ParenInsertionLoc = getLocForEndOfToken(Range.getEnd());
-    Diag(Loc, PD)
-      << /*zero-arg*/ 1 << Range
-      << (IsCallableWithAppend(E.get())
-          ? FixItHint::CreateInsertion(ParenInsertionLoc, "()")
-          : FixItHint());
-    notePlausibleOverloads(*this, Loc, Overloads, IsPlausibleResult);
+    bool IsMV = IsCPUDispatchCPUSpecificMultiVersion(E.get());
+    Diag(Loc, PD) << /*zero-arg*/ 1 << IsMV << Range
+                  << (IsCallableWithAppend(E.get())
+                          ? FixItHint::CreateInsertion(ParenInsertionLoc, "()")
+                          : FixItHint());
+    if (!IsMV)
+      notePlausibleOverloads(*this, Loc, Overloads, IsPlausibleResult);

     // FIXME: Try this before emitting the fixit, and suppress diagnostics
     // while doing so.
@@ -1757,8 +1779,10 @@ bool Sema::tryToRecoverWithCall(ExprResu

   if (!ForceComplain) return false;

-  Diag(Loc, PD) << /*not zero-arg*/ 0 << Range;
-  notePlausibleOverloads(*this, Loc, Overloads, IsPlausibleResult);
+  bool IsMV = IsCPUDispatchCPUSpecificMultiVersion(E.get());
+  Diag(Loc, PD) << /*not zero-arg*/ 0 << IsMV << Range;
+  if (!IsMV)
+    notePlausibleOverloads(*this, Loc, Overloads, IsPlausibleResult);
   E = ExprError();
   return true;
 }

Modified: cfe/trunk/lib/Sema/SemaDecl.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDecl.cpp?rev=337552&r1=337551&r2=337552&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaDecl.cpp (original)
+++ cfe/trunk/lib/Sema/SemaDecl.cpp Fri Jul 20 07:13:28 2018
@@ -9275,6 +9275,20 @@ bool Sema::shouldLinkDependentDeclWithPr
            D->getFriendObjectKind() != Decl::FOK_None);
 }

+namespace MultiVersioning {
+enum Type { None, Target, CPUSpecific, CPUDispatch};
+} // MultiVersionType
+
+static MultiVersioning::Type
+getMultiVersionType(const FunctionDecl *FD) {
+  if (FD->hasAttr<TargetAttr>())
+    return MultiVersioning::Target;
+  if (FD->hasAttr<CPUDispatchAttr>())
+    return MultiVersioning::CPUDispatch;
+  if (FD->hasAttr<CPUSpecificAttr>())
+    return MultiVersioning::CPUSpecific;
+  return MultiVersioning::None;
+}
 /// Check the target attribute of the function for MultiVersion
 /// validity.
 ///
@@ -9313,7 +9327,8 @@ static bool CheckMultiVersionValue(Sema

 static bool CheckMultiVersionAdditionalRules(Sema &S, const FunctionDecl *OldFD,
                                              const FunctionDecl *NewFD,
-                                             bool CausesMV) {
+                                             bool CausesMV,
+                                             MultiVersioning::Type MVType) {
   enum DoesntSupport {
     FuncTemplates = 0,
     VirtFuncs = 1,
@@ -9321,7 +9336,8 @@ static bool CheckMultiVersionAdditionalR
     Constructors = 3,
     Destructors = 4,
     DeletedFuncs = 5,
-    DefaultedFuncs = 6
+    DefaultedFuncs = 6,
+    ConstexprFuncs = 7,
   };
   enum Different {
     CallingConv = 0,
@@ -9332,46 +9348,73 @@ static bool CheckMultiVersionAdditionalR
     Linkage = 5
   };

+  bool IsCPUSpecificCPUDispatchMVType =
+      MVType == MultiVersioning::CPUDispatch ||
+      MVType == MultiVersioning::CPUSpecific;
+
+  if (OldFD && !OldFD->getType()->getAs<FunctionProtoType>()) {
+    S.Diag(OldFD->getLocation(), diag::err_multiversion_noproto);
+    S.Diag(NewFD->getLocation(), diag::note_multiversioning_caused_here);
+    return true;
+  }
+
+  if (!NewFD->getType()->getAs<FunctionProtoType>())
+    return S.Diag(NewFD->getLocation(), diag::err_multiversion_noproto);
+
+  if (!S.getASTContext().getTargetInfo().supportsMultiVersioning()) {
+    S.Diag(NewFD->getLocation(), diag::err_multiversion_not_supported);
+    if (OldFD)
+      S.Diag(OldFD->getLocation(), diag::note_previous_declaration);
+    return true;
+  }
+
   // For now, disallow all other attributes.  These should be opt-in, but
   // an analysis of all of them is a future FIXME.
   if (CausesMV && OldFD &&
       std::distance(OldFD->attr_begin(), OldFD->attr_end()) != 1) {
-    S.Diag(OldFD->getLocation(), diag::err_multiversion_no_other_attrs);
+    S.Diag(OldFD->getLocation(), diag::err_multiversion_no_other_attrs)
+        << IsCPUSpecificCPUDispatchMVType;
     S.Diag(NewFD->getLocation(), diag::note_multiversioning_caused_here);
     return true;
   }

   if (std::distance(NewFD->attr_begin(), NewFD->attr_end()) != 1)
-    return S.Diag(NewFD->getLocation(), diag::err_multiversion_no_other_attrs);
+    return S.Diag(NewFD->getLocation(), diag::err_multiversion_no_other_attrs)
+           << IsCPUSpecificCPUDispatchMVType;

   if (NewFD->getTemplatedKind() == FunctionDecl::TK_FunctionTemplate)
     return S.Diag(NewFD->getLocation(), diag::err_multiversion_doesnt_support)
-           << FuncTemplates;
+           << IsCPUSpecificCPUDispatchMVType << FuncTemplates;

   if (const auto *NewCXXFD = dyn_cast<CXXMethodDecl>(NewFD)) {
     if (NewCXXFD->isVirtual())
       return S.Diag(NewCXXFD->getLocation(),
                     diag::err_multiversion_doesnt_support)
-             << VirtFuncs;
+             << IsCPUSpecificCPUDispatchMVType << VirtFuncs;

     if (const auto *NewCXXCtor = dyn_cast<CXXConstructorDecl>(NewFD))
       return S.Diag(NewCXXCtor->getLocation(),
                     diag::err_multiversion_doesnt_support)
-             << Constructors;
+             << IsCPUSpecificCPUDispatchMVType << Constructors;

     if (const auto *NewCXXDtor = dyn_cast<CXXDestructorDecl>(NewFD))
       return S.Diag(NewCXXDtor->getLocation(),
                     diag::err_multiversion_doesnt_support)
-             << Destructors;
+             << IsCPUSpecificCPUDispatchMVType << Destructors;
   }

   if (NewFD->isDeleted())
     return S.Diag(NewFD->getLocation(), diag::err_multiversion_doesnt_support)
-           << DeletedFuncs;
+           << IsCPUSpecificCPUDispatchMVType << DeletedFuncs;

   if (NewFD->isDefaulted())
     return S.Diag(NewFD->getLocation(), diag::err_multiversion_doesnt_support)
-           << DefaultedFuncs;
+           << IsCPUSpecificCPUDispatchMVType << DefaultedFuncs;
+
+  if (NewFD->isConstexpr() && (MVType == MultiVersioning::CPUDispatch ||
+                               MVType == MultiVersioning::CPUSpecific))
+    return S.Diag(NewFD->getLocation(), diag::err_multiversion_doesnt_support)
+           << IsCPUSpecificCPUDispatchMVType << ConstexprFuncs;

   QualType NewQType = S.getASTContext().getCanonicalType(NewFD->getType());
   const auto *NewType = cast<FunctionType>(NewQType);
@@ -9379,7 +9422,7 @@ static bool CheckMultiVersionAdditionalR

   if (NewReturnType->isUndeducedType())
     return S.Diag(NewFD->getLocation(), diag::err_multiversion_doesnt_support)
-           << DeducedReturn;
+           << IsCPUSpecificCPUDispatchMVType << DeducedReturn;

   // Only allow transition to MultiVersion if it hasn't been used.
   if (OldFD && CausesMV && OldFD->isUsed(false))
@@ -9426,138 +9469,133 @@ static bool CheckMultiVersionAdditionalR
   return false;
 }

-/// Check the validity of a mulitversion function declaration.
-/// Also sets the multiversion'ness' of the function itself.
+/// Check the validity of a multiversion function declaration that is the
+/// first of its kind. Also sets the multiversion'ness' of the function itself.
 ///
 /// This sets NewFD->isInvalidDecl() to true if there was an error.
 ///
 /// Returns true if there was an error, false otherwise.
-static bool CheckMultiVersionFunction(Sema &S, FunctionDecl *NewFD,
-                                      bool &Redeclaration, NamedDecl *&OldDecl,
-                                      bool &MergeTypeWithPrevious,
-                                      LookupResult &Previous) {
-  const auto *NewTA = NewFD->getAttr<TargetAttr>();
-  if (NewFD->isMain()) {
-    if (NewTA && NewTA->isDefaultVersion()) {
-      S.Diag(NewFD->getLocation(), diag::err_multiversion_not_allowed_on_main);
-      NewFD->setInvalidDecl();
-      return true;
-    }
+static bool CheckMultiVersionFirstFunction(Sema &S, FunctionDecl *FD,
+                                           MultiVersioning::Type MVType,
+                                           const TargetAttr *TA,
+                                           const CPUDispatchAttr *CPUDisp,
+                                           const CPUSpecificAttr *CPUSpec) {
+  assert(MVType != MultiVersioning::None &&
+         "Function lacks multiversion attribute");
+
+  // Target only causes MV if it is default, otherwise this is a normal
+  // function.
+  if (MVType == MultiVersioning::Target && !TA->isDefaultVersion())
     return false;
-  }

-  // If there is no matching previous decl, only 'default' can
-  // cause MultiVersioning.
-  if (!OldDecl) {
-    if (NewTA && NewTA->isDefaultVersion()) {
-      if (!NewFD->getType()->getAs<FunctionProtoType>()) {
-        S.Diag(NewFD->getLocation(), diag::err_multiversion_noproto);
-        NewFD->setInvalidDecl();
-        return true;
-      }
-      if (CheckMultiVersionAdditionalRules(S, nullptr, NewFD, true)) {
-        NewFD->setInvalidDecl();
-        return true;
-      }
-      if (!S.getASTContext().getTargetInfo().supportsMultiVersioning()) {
-        S.Diag(NewFD->getLocation(), diag::err_multiversion_not_supported);
-        NewFD->setInvalidDecl();
-        return true;
-      }
+  if (MVType == MultiVersioning::Target && CheckMultiVersionValue(S, FD)) {
+    FD->setInvalidDecl();
+    return true;
+  }

-      NewFD->setIsMultiVersion();
-    }
-    return false;
+  if (CheckMultiVersionAdditionalRules(S, nullptr, FD, true, MVType)) {
+    FD->setInvalidDecl();
+    return true;
   }

-  if (OldDecl->getDeclContext()->getRedeclContext() !=
-      NewFD->getDeclContext()->getRedeclContext())
-    return false;
+  FD->setIsMultiVersion();
+  return false;
+}

-  FunctionDecl *OldFD = OldDecl->getAsFunction();
-  // Unresolved 'using' statements (the other way OldDecl can be not a function)
-  // likely cannot cause a problem here.
-  if (!OldFD)
-    return false;
+static bool CheckTargetCausesMultiVersioning(
+    Sema &S, FunctionDecl *OldFD, FunctionDecl *NewFD, const TargetAttr *NewTA,
+    bool &Redeclaration, NamedDecl *&OldDecl, bool &MergeTypeWithPrevious,
+    LookupResult &Previous) {
+  const auto *OldTA = OldFD->getAttr<TargetAttr>();
+  TargetAttr::ParsedTargetAttr NewParsed = NewTA->parse();
+  // Sort order doesn't matter, it just needs to be consistent.
+  llvm::sort(NewParsed.Features.begin(), NewParsed.Features.end());

-  if (!OldFD->isMultiVersion() && !NewTA)
+  // If the old decl is NOT MultiVersioned yet, and we don't cause that
+  // to change, this is a simple redeclaration.
+  if (!OldTA || OldTA->getFeaturesStr() == NewTA->getFeaturesStr())
     return false;

-  if (OldFD->isMultiVersion() && !NewTA) {
-    S.Diag(NewFD->getLocation(), diag::err_target_required_in_redecl);
+  // Otherwise, this decl causes MultiVersioning.
+  if (!S.getASTContext().getTargetInfo().supportsMultiVersioning()) {
+    S.Diag(NewFD->getLocation(), diag::err_multiversion_not_supported);
+    S.Diag(OldFD->getLocation(), diag::note_previous_declaration);
     NewFD->setInvalidDecl();
     return true;
   }

-  TargetAttr::ParsedTargetAttr NewParsed = NewTA->parse();
-  // Sort order doesn't matter, it just needs to be consistent.
-  llvm::sort(NewParsed.Features.begin(), NewParsed.Features.end());
+  if (CheckMultiVersionAdditionalRules(S, OldFD, NewFD, true,
+                                       MultiVersioning::Target)) {
+    NewFD->setInvalidDecl();
+    return true;
+  }

-  const auto *OldTA = OldFD->getAttr<TargetAttr>();
-  if (!OldFD->isMultiVersion()) {
-    // If the old decl is NOT MultiVersioned yet, and we don't cause that
-    // to change, this is a simple redeclaration.
-    if (!OldTA || OldTA->getFeaturesStr() == NewTA->getFeaturesStr())
-      return false;
+  if (CheckMultiVersionValue(S, NewFD)) {
+    NewFD->setInvalidDecl();
+    return true;
+  }

-    // Otherwise, this decl causes MultiVersioning.
-    if (!S.getASTContext().getTargetInfo().supportsMultiVersioning()) {
-      S.Diag(NewFD->getLocation(), diag::err_multiversion_not_supported);
-      S.Diag(OldFD->getLocation(), diag::note_previous_declaration);
-      NewFD->setInvalidDecl();
-      return true;
-    }
+  if (CheckMultiVersionValue(S, OldFD)) {
+    S.Diag(NewFD->getLocation(), diag::note_multiversioning_caused_here);
+    NewFD->setInvalidDecl();
+    return true;
+  }

-    if (!OldFD->getType()->getAs<FunctionProtoType>()) {
-      S.Diag(OldFD->getLocation(), diag::err_multiversion_noproto);
-      S.Diag(NewFD->getLocation(), diag::note_multiversioning_caused_here);
-      NewFD->setInvalidDecl();
-      return true;
-    }
+  TargetAttr::ParsedTargetAttr OldParsed =
+      OldTA->parse(std::less<std::string>());

-    if (CheckMultiVersionValue(S, NewFD)) {
-      NewFD->setInvalidDecl();
-      return true;
-    }
+  if (OldParsed == NewParsed) {
+    S.Diag(NewFD->getLocation(), diag::err_multiversion_
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