Implement -fsemantic-interposition

First attempt at implementing -fsemantic-interposition.

Rely on GlobalValue::isInterposable that already captures most of the expected
behavior.

Rely on a ModuleFlag to state whether we should respect SemanticInterposition or
not. The default remains no.

So this should be a no-op if -fsemantic-interposition isn't used, and if it is,
isInterposable being already used in most optimisation, they should honor it
properly.

Note that it only impacts architecture compiled with -fPIC and no pie.

Differential Revision: https://reviews.llvm.org/D72829

1 files changed, 6 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 03c3fec5ebec..6a43b6bba627 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -483,6 +483,11 @@ void CodeGenModule::Release() {
     getModule().addModuleFlag(llvm::Module::Max, "Dwarf Version",
                               CodeGenOpts.DwarfVersion);
   }
+
+  if (Context.getLangOpts().SemanticInterposition)
+    // Require various optimization to respect semantic interposition.
+    getModule().setSemanticInterposition(1);
+
   if (CodeGenOpts.EmitCodeView) {
     // Indicate that we want CodeView in the metadata.
     getModule().addModuleFlag(llvm::Module::Warning, "CodeView", 1);
@@ -872,7 +877,7 @@ static bool shouldAssumeDSOLocal(const CodeGenModule &CGM,
   if (isa<llvm::Function>(GV) && !CGOpts.NoPLT && RM == llvm::Reloc::Static)
     return true;
 
-  // Otherwise don't assue it is local.
+  // Otherwise don't assume it is local.
   return false;
 }