Refactor how -fno-semantic-interposition sets dso_local on default visibility external linkage definitions

The idea is that the CC1 default for ELF should set dso_local on default
visibility external linkage definitions in the default -mrelocation-model pic
mode (-fpic/-fPIC) to match COFF/Mach-O and make output IR similar.

The refactoring is made available by 2820a2ca3a0e69c3f301845420e0067ffff2251b.

Currently only x86 supports local aliases. We move the decision to the driver.
There are three CC1 states:

* -fsemantic-interposition: make some linkages interposable and make default visibility external linkage definitions dso_preemptable.
* (default): selected if the target supports .Lfoo$local: make default visibility external linkage definitions dso_local
* -fhalf-no-semantic-interposition: if neither option is set or the target does not support .Lfoo$local: like -fno-semantic-interposition but local aliases are not used. So references can be interposed if not optimized out.

Add -fhalf-no-semantic-interposition to a few tests using the half-based semantic interposition behavior.

1 files changed, 0 insertions, 7 deletions

diff --git a/llvm/lib/IR/Module.cpp b/llvm/lib/IR/Module.cpp
index b6fde57..b4f10e2 100644
--- a/llvm/lib/IR/Module.cpp
+++ b/llvm/lib/IR/Module.cpp
@@ -601,13 +601,6 @@ void Module::setSemanticInterposition(bool SI) {
   addModuleFlag(ModFlagBehavior::Error, "SemanticInterposition", SI);
 }
 
-bool Module::noSemanticInterposition() const {
-  // Conservatively require an explicit zero value for now.
-  Metadata *MF = getModuleFlag("SemanticInterposition");
-  auto *Val = cast_or_null<ConstantAsMetadata>(MF);
-  return Val && cast<ConstantInt>(Val->getValue())->getZExtValue() == 0;
-}
-
 void Module::setOwnedMemoryBuffer(std::unique_ptr<MemoryBuffer> MB) {
   OwnedMemoryBuffer = std::move(MB);
 }