Merging r344100:

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r344100 | emaste | 2018-10-09 17:34:17 -0700 (Tue, 09 Oct 2018) | 16 lines

clang: Allow ifunc resolvers to accept arguments

When ifunc support was added to Clang (r265917) it did not allow
resolvers to take function arguments.  This was based on GCC's
documentation, which states resolvers return a pointer and take no
arguments.

However, GCC actually allows resolvers to take arguments, and glibc (on
non-x86 platforms) and FreeBSD (on x86 and arm64) pass some CPU
identification information as arguments to ifunc resolvers.  I believe
GCC's documentation is simply incorrect / out-of-date.

FreeBSD already removed the prohibition in their in-tree Clang copy.

Differential Revision:	https://reviews.llvm.org/D52703

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llvm-svn: 348012

Author: tstellar

clang/include/clang/Basic/AttrDocs.td

@@ -3364,7 +3364,7 @@ def IFuncDocs : Documentation {
   let Content = [{
 ``__attribute__((ifunc("resolver")))`` is used to mark that the address of a declaration should be resolved at runtime by calling a resolver function.
 
-The symbol name of the resolver function is given in quotes.  A function with this name (after mangling) must be defined in the current translation unit; it may be ``static``.  The resolver function should take no arguments and return a pointer.
+The symbol name of the resolver function is given in quotes.  A function with this name (after mangling) must be defined in the current translation unit; it may be ``static``.  The resolver function should return a pointer.
 
 The ``ifunc`` attribute may only be used on a function declaration.  A function declaration with an ``ifunc`` attribute is considered to be a definition of the declared entity.  The entity must not have weak linkage; for example, in C++, it cannot be applied to a declaration if a definition at that location would be considered inline.
 

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -2857,8 +2857,6 @@ def err_cyclic_alias : Error<
   "%select{alias|ifunc}0 definition is part of a cycle">;
 def err_ifunc_resolver_return : Error<
   "ifunc resolver function must return a pointer">;
-def err_ifunc_resolver_params : Error<
-  "ifunc resolver function must have no parameters">;
 def warn_attribute_wrong_decl_type_str : Warning<
   "%0 attribute only applies to %1">, InGroup<IgnoredAttributes>;
 def err_attribute_wrong_decl_type_str : Error<

clang/lib/CodeGen/CodeGenModule.cpp

@@ -320,8 +320,6 @@ void CodeGenModule::checkAliases() {
       assert(FTy);
       if (!FTy->getReturnType()->isPointerTy())
         Diags.Report(Location, diag::err_ifunc_resolver_return);
-      if (FTy->getNumParams())
-        Diags.Report(Location, diag::err_ifunc_resolver_params);
     }
 
     llvm::Constant *Aliasee = Alias->getIndirectSymbol();

clang/test/Sema/attr-ifunc.c

@@ -27,10 +27,6 @@ void f4_ifunc() {}
 void f4() __attribute__((ifunc("f4_ifunc")));
 //expected-error@-1 {{ifunc resolver function must return a pointer}}
 
-void* f5_ifunc(int i) { return 0; }
-void f5() __attribute__((ifunc("f5_ifunc")));
-//expected-error@-1 {{ifunc resolver function must have no parameters}}
-
 #else
 void f1a() __asm("f1");
 void f1a() {}