[clang][FMV] Fix crash with cpu_specific attribute.

Raised here #115299.

The commit a2d3099 introduced `replaceDeclarationWith`, but it
shouldn't be called by the fallthrough code which handles the
cpu_specific attribute.

Author: labrinea

clang/lib/CodeGen/CodeGenModule.cpp

@@ -4597,8 +4597,6 @@ llvm::Constant *CodeGenModule::GetOrCreateMultiVersionResolver(GlobalDecl GD) {
   assert(isa<llvm::GlobalValue>(Resolver) &&
          "Resolver should be created for the first time");
   SetCommonAttributes(FD, cast<llvm::GlobalValue>(Resolver));
-  if (ResolverGV)
-    replaceDeclarationWith(ResolverGV, Resolver);
   return Resolver;
 }
 

clang/test/CodeGen/attr-cpuspecific.c

@@ -114,8 +114,8 @@ void ThreeVersionsSameAttr(void){}
 // CHECK: define {{.*}}void @ThreeVersionsSameAttr.Z() #[[K]]
 
 ATTR(cpu_specific(knl))
-void CpuSpecificNoDispatch(void) {}
-// CHECK: define {{.*}}void @CpuSpecificNoDispatch.Z() #[[K:[0-9]+]]
+void CpuSpecificNoDispatch(void (*f)(void)) {}
+// CHECK: define {{.*}}void @CpuSpecificNoDispatch.Z(ptr noundef %f) #[[K:[0-9]+]]
 
 ATTR(cpu_dispatch(knl))
 void OrderDispatchUsageSpecific(void);
@@ -151,9 +151,9 @@ void usages(void) {
   ThreeVersionsSameAttr();
   // LINUX: @ThreeVersionsSameAttr.ifunc()
   // WINDOWS: @ThreeVersionsSameAttr()
-  CpuSpecificNoDispatch();
-  // LINUX: @CpuSpecificNoDispatch.ifunc()
-  // WINDOWS: @CpuSpecificNoDispatch()
+  CpuSpecificNoDispatch((void (*)(void))CpuSpecificNoDispatch);
+  // LINUX: @CpuSpecificNoDispatch.ifunc(ptr noundef @CpuSpecificNoDispatch.ifunc)
+  // WINDOWS: @CpuSpecificNoDispatch(ptr noundef @CpuSpecificNoDispatch)
   OrderDispatchUsageSpecific();
   // LINUX: @OrderDispatchUsageSpecific.ifunc()
   // WINDOWS: @OrderDispatchUsageSpecific()
@@ -162,7 +162,7 @@ void usages(void) {
   // WINDOWS: @OrderSpecificUsageDispatch()
 }
 
-// LINUX: declare void @CpuSpecificNoDispatch.ifunc()
+// LINUX: declare void @CpuSpecificNoDispatch.ifunc(ptr)
 
 // has an extra config to emit!
 ATTR(cpu_dispatch(ivybridge, knl, atom))