First step in fixing PR8927:

Add a unnamed_addr bit to global variables and functions. This will be used
to indicate that the address is not significant and therefore the constant
or function can be merged with others.

If an optimization pass can show that an address is not used, it can set this.

Examples of things that can have this set by the FE are globals created to
hold string literals and C++ constructors.

Adding unnamed_addr to a non-const global should have no effect unless
an optimization can transform that global into a constant.

Aliases are not allowed to have unnamed_addr since I couldn't figure
out any use for it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123063 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 4 insertions, 0 deletions

diff --git a/lib/VMCore/AsmWriter.cpp b/lib/VMCore/AsmWriter.cpp
index 7a1b7dd..3fefbbc 100644
--- a/lib/VMCore/AsmWriter.cpp
+++ b/lib/VMCore/AsmWriter.cpp
@@ -1459,6 +1459,7 @@ void AssemblyWriter::printGlobal(const GlobalVariable *GV) {
   if (GV->isThreadLocal()) Out << "thread_local ";
   if (unsigned AddressSpace = GV->getType()->getAddressSpace())
     Out << "addrspace(" << AddressSpace << ") ";
+  if (GV->hasUnnamedAddr()) Out << "unnamed_addr ";
   Out << (GV->isConstant() ? "constant " : "global ");
   TypePrinter.print(GV->getType()->getElementType(), Out);
 
@@ -1589,6 +1590,8 @@ void AssemblyWriter::printFunction(const Function *F) {
   Attributes RetAttrs = Attrs.getRetAttributes();
   if (RetAttrs != Attribute::None)
     Out <<  Attribute::getAsString(Attrs.getRetAttributes()) << ' ';
+  if (F->hasUnnamedAddr())
+    Out << "unnamed_addr ";
   TypePrinter.print(F->getReturnType(), Out);
   Out << ' ';
   WriteAsOperandInternal(Out, F, &TypePrinter, &Machine, F->getParent());
diff --git a/lib/VMCore/Verifier.cpp b/lib/VMCore/Verifier.cpp
index 2b87619..58ec6fe 100644
--- a/lib/VMCore/Verifier.cpp
+++ b/lib/VMCore/Verifier.cpp
@@ -484,6 +484,7 @@ void Verifier::visitGlobalAlias(GlobalAlias &GA) {
           "Aliasee cannot be NULL!", &GA);
   Assert1(GA.getType() == GA.getAliasee()->getType(),
           "Alias and aliasee types should match!", &GA);
+  Assert1(!GA.hasUnnamedAddr(), "Alias cannot have unnamed_addr!", &GA);
 
   if (!isa<GlobalValue>(GA.getAliasee())) {
     const ConstantExpr *CE = dyn_cast<ConstantExpr>(GA.getAliasee());