From 07ab20203fb4254f6152c9a7176732fe199adccd Mon Sep 17 00:00:00 2001
From: Sebastian Redl <sebastian.redl@getdesigned.at>
Date: Sat, 17 Oct 2009 21:12:09 +0000
Subject: [PATCH] When resolving the address of an overloaded function or
 function template, mark the result as referenced.

The most important effect of this is that function templates only referenced by address expressions now get instantiated. This, in turn, means that Hello World compiles with the Apache stdcxx library even when using endl.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@84363 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaOverload.cpp                 | 31 +++++++++++++++--------
 test/CodeGenCXX/address-of-fntemplate.cpp |  3 +--
 2 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index 5f874e8dbc..0f2256b6bc 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -4334,8 +4334,11 @@ Sema::ResolveAddressOfOverloadedFunction(Expr *From, QualType ToType,
   // If there were 0 or 1 matches, we're done.
   if (Matches.empty())
     return 0;
-  else if (Matches.size() == 1)
-    return *Matches.begin();
+  else if (Matches.size() == 1) {
+    FunctionDecl *Result = *Matches.begin();
+    MarkDeclarationReferenced(From->getLocStart(), Result);
+    return Result;
+  }
 
   // C++ [over.over]p4:
   //   If more than one function is selected, [...]
@@ -4351,14 +4354,17 @@ Sema::ResolveAddressOfOverloadedFunction(Expr *From, QualType ToType,
     // two-pass algorithm (similar to the one used to identify the
     // best viable function in an overload set) that identifies the
     // best function template (if it exists).
-    llvm::SmallVector<FunctionDecl *, 8> TemplateMatches(Matches.begin(), 
+    llvm::SmallVector<FunctionDecl *, 8> TemplateMatches(Matches.begin(),
                                                          Matches.end());
-    return getMostSpecialized(TemplateMatches.data(), TemplateMatches.size(), 
-                              TPOC_Other, From->getLocStart(),
-                              PDiag(),
-                              PDiag(diag::err_addr_ovl_ambiguous)
-                              << TemplateMatches[0]->getDeclName(), 
-                              PDiag(diag::err_ovl_template_candidate));
+    FunctionDecl *Result =
+        getMostSpecialized(TemplateMatches.data(), TemplateMatches.size(),
+                           TPOC_Other, From->getLocStart(),
+                           PDiag(),
+                           PDiag(diag::err_addr_ovl_ambiguous)
+                               << TemplateMatches[0]->getDeclName(),
+                           PDiag(diag::err_ovl_template_candidate));
+    MarkDeclarationReferenced(From->getLocStart(), Result);
+    return Result;
   }
 
   //   [...] any function template specializations in the set are
@@ -4370,8 +4376,11 @@ Sema::ResolveAddressOfOverloadedFunction(Expr *From, QualType ToType,
   
   // [...] After such eliminations, if any, there shall remain exactly one
   // selected function.
-  if (RemainingMatches.size() == 1)
-    return RemainingMatches.front();
+  if (RemainingMatches.size() == 1) {
+    FunctionDecl *Result = RemainingMatches.front();
+    MarkDeclarationReferenced(From->getLocStart(), Result);
+    return Result;
+  }
 
   // FIXME: We should probably return the same thing that BestViableFunction
   // returns (even if we issue the diagnostics here).
diff --git a/test/CodeGenCXX/address-of-fntemplate.cpp b/test/CodeGenCXX/address-of-fntemplate.cpp
index cbf042551d..9a1364325f 100644
--- a/test/CodeGenCXX/address-of-fntemplate.cpp
+++ b/test/CodeGenCXX/address-of-fntemplate.cpp
@@ -2,8 +2,7 @@
 template <typename T> void f(T) {}
 
 void test() {
-  // FIXME: This emits only a declaration instead of a definition
   // CHECK: @_Z1fIiEvT_
   void (*p)(int) = &f;
 }
-// CHECK-disabled: define linkonce_odr void @_Z1fIiEvT_
+// CHECK: define linkonce_odr void @_Z1fIiEvT_
-- 
2.40.0