Add support for handling ifuncs to GlobalValue::getBaseObject

[tejohnson]

Summary

All GlobalIndirectSymbol types (not just GlobalAlias) should return
their base object.

Without this patch LTO would warn "Unable to determine comdat of
alias!" for an ifunc.

[tejohnson]

Update per review

llvm/trunk/lib/IR/Globals.cpp

if (isELF && hasDefaultVisibility() && !hasLocalLinkage())
     return false;
 
   return true;
 }
 
 const GlobalObject *GlobalValue::getBaseObject() const {
   if (auto *GO = dyn_cast<GlobalObject>(this))
     return GO;
-  if (auto *GA = dyn_cast<GlobalAlias>(this))
+  if (auto *GA = dyn_cast<GlobalIndirectSymbol>(this))
     return GA->getBaseObject();
   return nullptr;
 }
 
 bool GlobalValue::isAbsoluteSymbolRef() const {
   auto *GO = dyn_cast<GlobalObject>(this);
   if (!GO)
     return false;

llvm/trunk/test/LTO/Resolution/X86/ifunc.ll

+; RUN: opt -module-summary -o %t.bc %s
+; RUN: llvm-lto2 run %t.bc -r %t.bc,foo,pl -o %t2
+; RUN: llvm-nm %t2.0 | FileCheck %s
+; CHECK: T foo
+; CHECK: t foo_ifunc
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@foo = ifunc i32 (i32), i64 ()* @foo_ifunc
+
+define internal i64 @foo_ifunc() {
+entry:
+  ret i64 0
+}

llvm/trunk/test/Object/X86/nm-ir.ll

 ; RUN: llvm-as %s -o - | llvm-nm - | FileCheck %s
 
 ; CHECK: D a1
 ; CHECK-NEXT: d a2
 ; CHECK-NEXT: T f1
 ; CHECK-NEXT: t f2
 ; CHECK-NEXT: W f3
 ; CHECK-NEXT: U f4
 ; CHECK-NEXT: w f5
 ; CHECK-NEXT: D g1
 ; CHECK-NEXT: d g2
 ; CHECK-NEXT: C g3
 ; CHECK-NOT: g4
 ; CHECK-NEXT: T global_asm_sym
-; CHECK-NEXT: D ifunc_f1
+; CHECK-NEXT: T ifunc_f1
 ; CHECK-NEXT: t local_asm_sym
 ; CHECK-NEXT: U undef_asm_sy
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 module asm ".global global_asm_sym"
 module asm "global_asm_sym:"