CPUDispatch- allow out of line member definitions

ICC permits this, and after some extensive testing it looks like we can
support this with very little trouble.  We intentionally don't choose to
do this with attribute-target (despite it likely working as well!)
  because GCC does not support that, and introducing said
  incompatibility doesn't seem worth it.

GitOrigin-RevId: 92aba5ae49a6970c43bead0afd1e52c83fe44e6e
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 1d57d8e..73303b9 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -9693,6 +9693,10 @@
             (D.getCXXScopeSpec().getScopeRep()->isDependent() ||
              (!Previous.empty() && CurContext->isDependentContext()))) {
           // ignore these
+        } else if (NewFD->isCPUDispatchMultiVersion() ||
+                   NewFD->isCPUSpecificMultiVersion()) {
+          // ignore this, we allow the redeclaration behavior here to create new
+          // versions of the function.
         } else {
           // The user tried to provide an out-of-line definition for a
           // function that is a member of a class or namespace, but there
diff --git a/test/CodeGenCXX/attr-cpuspecific-outoflinedefs.cpp b/test/CodeGenCXX/attr-cpuspecific-outoflinedefs.cpp
new file mode 100644
index 0000000..a34a0b8
--- /dev/null
+++ b/test/CodeGenCXX/attr-cpuspecific-outoflinedefs.cpp
@@ -0,0 +1,97 @@
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -o - %s | FileCheck %s --check-prefix=LINUX
+// RUN: %clang_cc1 -triple x86_64-windows-pc -fms-compatibility -emit-llvm -o - %s | FileCheck %s --check-prefix=WINDOWS
+
+struct OutOfLineDefs {
+  int foo(int);
+  int foo(int, int);
+  __attribute__((cpu_specific(atom))) int foo(int, int, int) { return 1; }
+};
+
+int __attribute__((cpu_specific(atom))) OutOfLineDefs::foo(int) {
+  return 1;
+}
+int __attribute__((cpu_specific(ivybridge))) OutOfLineDefs::foo(int) {
+  return 2;
+}
+int __attribute__((cpu_dispatch(ivybridge, atom))) OutOfLineDefs::foo(int) {
+}
+
+int __attribute__((cpu_specific(atom))) OutOfLineDefs::foo(int, int) {
+  return 1;
+}
+int __attribute__((cpu_specific(ivybridge))) OutOfLineDefs::foo(int, int) {
+  return 2;
+}
+int __attribute__((cpu_dispatch(ivybridge, atom)))
+OutOfLineDefs::foo(int, int) {
+}
+
+int __attribute__((cpu_specific(ivybridge))) OutOfLineDefs::foo(int, int, int) {
+  return 2;
+}
+int __attribute__((cpu_specific(sandybridge)))
+OutOfLineDefs::foo(int, int, int) {
+  return 3;
+}
+int __attribute__((cpu_dispatch(sandybridge, ivybridge, atom)))
+OutOfLineDefs::foo(int, int, int) {
+}
+
+// IFunc definitions, Linux only.
+// LINUX: @_ZN13OutOfLineDefs3fooEi = weak_odr alias i32 (%struct.OutOfLineDefs*, i32), i32 (%struct.OutOfLineDefs*, i32)* @_ZN13OutOfLineDefs3fooEi.ifunc
+// LINUX: @_ZN13OutOfLineDefs3fooEii = weak_odr alias i32 (%struct.OutOfLineDefs*, i32, i32), i32 (%struct.OutOfLineDefs*, i32, i32)* @_ZN13OutOfLineDefs3fooEii.ifunc
+// LINUX: @_ZN13OutOfLineDefs3fooEiii = weak_odr alias i32 (%struct.OutOfLineDefs*, i32, i32, i32), i32 (%struct.OutOfLineDefs*, i32, i32, i32)* @_ZN13OutOfLineDefs3fooEiii.ifunc
+
+// LINUX: @_ZN13OutOfLineDefs3fooEi.ifunc = weak_odr ifunc i32 (%struct.OutOfLineDefs*, i32), i32 (%struct.OutOfLineDefs*, i32)* ()* @_ZN13OutOfLineDefs3fooEi.resolver
+// LINUX: @_ZN13OutOfLineDefs3fooEii.ifunc = weak_odr ifunc i32 (%struct.OutOfLineDefs*, i32, i32), i32 (%struct.OutOfLineDefs*, i32, i32)* ()* @_ZN13OutOfLineDefs3fooEii.resolver
+// LINUX: @_ZN13OutOfLineDefs3fooEiii.ifunc = weak_odr ifunc i32 (%struct.OutOfLineDefs*, i32, i32, i32), i32 (%struct.OutOfLineDefs*, i32, i32, i32)* ()* @_ZN13OutOfLineDefs3fooEiii.resolver
+
+// Arity 1 version:
+// LINUX: define dso_local i32 @_ZN13OutOfLineDefs3fooEi.O
+// LINUX: define dso_local i32 @_ZN13OutOfLineDefs3fooEi.S
+// LINUX: define weak_odr i32 (%struct.OutOfLineDefs*, i32)* @_ZN13OutOfLineDefs3fooEi.resolver()
+// LINUX: ret i32 (%struct.OutOfLineDefs*, i32)* @_ZN13OutOfLineDefs3fooEi.S
+// LINUX: ret i32 (%struct.OutOfLineDefs*, i32)* @_ZN13OutOfLineDefs3fooEi.O
+// LINUX: call void @llvm.trap
+
+// WINDOWS: define dso_local i32 @"?foo@OutOfLineDefs@@QEAAHH@Z.O"
+// WINDOWS: define dso_local i32 @"?foo@OutOfLineDefs@@QEAAHH@Z.S"
+// WINDOWS: define weak_odr dso_local i32 @"?foo@OutOfLineDefs@@QEAAHH@Z"(%struct.OutOfLineDefs* %0, i32 %1)
+// WINDOWS: musttail call i32 @"?foo@OutOfLineDefs@@QEAAHH@Z.S"(%struct.OutOfLineDefs* %0, i32 %1)
+// WINDOWS: musttail call i32 @"?foo@OutOfLineDefs@@QEAAHH@Z.O"(%struct.OutOfLineDefs* %0, i32 %1)
+// WINDOWS: call void @llvm.trap
+
+// Arity 2 version:
+// LINUX: define dso_local i32 @_ZN13OutOfLineDefs3fooEii.O
+// LINUX: define dso_local i32 @_ZN13OutOfLineDefs3fooEii.S
+// LINUX: define weak_odr i32 (%struct.OutOfLineDefs*, i32, i32)* @_ZN13OutOfLineDefs3fooEii.resolver()
+// LINUX: ret i32 (%struct.OutOfLineDefs*, i32, i32)* @_ZN13OutOfLineDefs3fooEii.S
+// LINUX: ret i32 (%struct.OutOfLineDefs*, i32, i32)* @_ZN13OutOfLineDefs3fooEii.O
+// LINUX: call void @llvm.trap
+
+// WINDOWS: define dso_local i32 @"?foo@OutOfLineDefs@@QEAAHHH@Z.O"
+// WINDOWS: define dso_local i32 @"?foo@OutOfLineDefs@@QEAAHHH@Z.S"
+// WINDOWS: define weak_odr dso_local i32 @"?foo@OutOfLineDefs@@QEAAHHH@Z"(%struct.OutOfLineDefs* %0, i32 %1, i32 %2)
+// WINDOWS: musttail call i32 @"?foo@OutOfLineDefs@@QEAAHHH@Z.S"(%struct.OutOfLineDefs* %0, i32 %1, i32 %2)
+// WINDOWS: musttail call i32 @"?foo@OutOfLineDefs@@QEAAHHH@Z.O"(%struct.OutOfLineDefs* %0, i32 %1, i32 %2)
+// WINDOWS: call void @llvm.trap
+
+// Arity 3 version:
+// LINUX: define dso_local i32 @_ZN13OutOfLineDefs3fooEiii.S
+// LINUX: define dso_local i32 @_ZN13OutOfLineDefs3fooEiii.R
+// LINUX: define weak_odr i32 (%struct.OutOfLineDefs*, i32, i32, i32)* @_ZN13OutOfLineDefs3fooEiii.resolver()
+// LINUX: ret i32 (%struct.OutOfLineDefs*, i32, i32, i32)* @_ZN13OutOfLineDefs3fooEiii.R
+// LINUX: ret i32 (%struct.OutOfLineDefs*, i32, i32, i32)* @_ZN13OutOfLineDefs3fooEiii.S
+// LINUX: ret i32 (%struct.OutOfLineDefs*, i32, i32, i32)* @_ZN13OutOfLineDefs3fooEiii.O
+// LINUX: call void @llvm.trap
+// LINUX: define linkonce_odr i32 @_ZN13OutOfLineDefs3fooEiii.O
+
+// WINDOWS: define dso_local i32 @"?foo@OutOfLineDefs@@QEAAHHHH@Z.S"
+// WINDOWS: define dso_local i32 @"?foo@OutOfLineDefs@@QEAAHHHH@Z.R"
+// WINDOWS: define weak_odr dso_local i32 @"?foo@OutOfLineDefs@@QEAAHHHH@Z"(%struct.OutOfLineDefs* %0, i32 %1, i32 %2, i32 %3)
+// WINDOWS: musttail call i32 @"?foo@OutOfLineDefs@@QEAAHHHH@Z.R"(%struct.OutOfLineDefs* %0, i32 %1, i32 %2, i32 %3)
+// WINDOWS: musttail call i32 @"?foo@OutOfLineDefs@@QEAAHHHH@Z.S"(%struct.OutOfLineDefs* %0, i32 %1, i32 %2, i32 %3)
+// WINDOWS: musttail call i32 @"?foo@OutOfLineDefs@@QEAAHHHH@Z.O"(%struct.OutOfLineDefs* %0, i32 %1, i32 %2, i32 %3)
+// WINDOWS: call void @llvm.trap
+// WINDOWS: define linkonce_odr dso_local i32 @"?foo@OutOfLineDefs@@QEAAHHHH@Z.O"
+
diff --git a/test/SemaCXX/attr-cpuspecific.cpp b/test/SemaCXX/attr-cpuspecific.cpp
index 7ec8c6c..861711b 100644
--- a/test/SemaCXX/attr-cpuspecific.cpp
+++ b/test/SemaCXX/attr-cpuspecific.cpp
@@ -98,14 +98,12 @@
   SpecialFuncs& __attribute__((cpu_specific(atom))) operator=(SpecialFuncs&&) = delete;
 };
 
-struct BadOutOfLine {
+struct OutOfLine {
   int __attribute__((cpu_specific(atom, ivybridge))) foo(int);
 };
 
-int __attribute__((cpu_specific(atom, ivybridge))) BadOutOfLine::foo(int) { return 0; }
-// expected-error@+2 {{out-of-line definition of 'foo' does not match any declaration in 'BadOutOfLine'}}
-// expected-note@-2 {{member declaration nearly matches}}
-int __attribute__((cpu_specific(sandybridge))) BadOutOfLine::foo(int) { return 1; }
+int __attribute__((cpu_specific(atom, ivybridge))) OutOfLine::foo(int) { return 0; }
+int __attribute__((cpu_specific(sandybridge))) OutOfLine::foo(int) { return 1; }
 
 // Ensure Cpp Spelling works.
 [[clang::cpu_specific(ivybridge,atom)]] int CppSpelling(){}