[InstrProf] Don't take the address of alwaysinline available_externally functions

Doing so breaks compilation of the following C program
(under -fprofile-instr-generate):

 __attribute__((always_inline)) inline int foo() { return 0; }

 int main() { return foo(); }

At link time, we fail because taking the address of an
available_externally function creates an undefined external reference,
which the TU cannot provide.

Emitting the function definition into the object file at all appears to
be a violation of the langref: "Globals with 'available_externally'
linkage are never emitted into the object file corresponding to the LLVM
module."

Differential Revision: https://reviews.llvm.org/D34134

llvm-svn: 305327

lib/Transforms/Instrumentation/InstrProfiling.cpp

@@ -343,14 +343,24 @@ static std::string getVarName(InstrProfIncrementInst *Inc, StringRef Prefix) {
 
 static inline bool shouldRecordFunctionAddr(Function *F) {
   // Check the linkage
+  bool HasAvailableExternallyLinkage = F->hasAvailableExternallyLinkage();
   if (!F->hasLinkOnceLinkage() && !F->hasLocalLinkage() &&
-      !F->hasAvailableExternallyLinkage())
+      !HasAvailableExternallyLinkage)
     return true;
+
+  // A function marked 'alwaysinline' with available_externally linkage can't
+  // have its address taken. Doing so would create an undefined external ref to
+  // the function, which would fail to link.
+  if (HasAvailableExternallyLinkage &&
+      F->hasFnAttribute(Attribute::AlwaysInline))
+    return false;
+
   // Prohibit function address recording if the function is both internal and
   // COMDAT. This avoids the profile data variable referencing internal symbols
   // in COMDAT.
   if (F->hasLocalLinkage() && F->hasComdat())
     return false;
+
   // Check uses of this function for other than direct calls or invokes to it.
   // Inline virtual functions have linkeOnceODR linkage. When a key method
   // exists, the vtable will only be emitted in the TU where the key method

test/Instrumentation/InstrProfiling/always_inline.ll

@@ -0,0 +1,28 @@
+; Check that '__attribute__((always_inline)) inline' functions are inlined.
+
+; RUN: opt < %s -mtriple=x86_64-apple-macosx10.10.0 -instrprof -inline -S | FileCheck %s 
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.13.0"
+
+@__profn_foo = linkonce_odr hidden constant [3 x i8] c"foo"
+
+; CHECK-LABEL: @main
+; CHECK-NOT: call
+define i32 @main() {
+entry:
+  %call = call i32 @foo()
+  ret i32 %call
+}
+
+declare void @llvm.instrprof.increment(i8*, i64, i32, i32) #0
+
+; CHECK-NOT: define available_externally i32 @foo
+define available_externally i32 @foo() #1 {
+entry:
+  call void @llvm.instrprof.increment(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @__profn_foo, i32 0, i32 0), i64 0, i32 1, i32 0)
+  ret i32 0
+}
+
+attributes #0 = { nounwind }
+attributes #1 = { alwaysinline }