[CIR][CIRGen] Ensure default visibility for local linkage functions (#990)

LLVM's verifier enforces this, which was previously causing us to fail
verification. This is a bit of a band-aid; the overall linkage and
visibility setting flow needs some work to match the original.

Author: smeenai

clang/lib/CIR/CodeGen/CIRGenModule.cpp

@@ -2608,8 +2608,15 @@ void CIRGenModule::setFunctionAttributes(GlobalDecl globalDecl,
 
   // TODO(cir): Complete the remaining part of the function.
   assert(!MissingFeatures::setFunctionAttributes());
-  auto decl = globalDecl.getDecl();
-  func.setGlobalVisibilityAttr(getGlobalVisibilityAttrFromDecl(decl));
+
+  // TODO(cir): This needs a lot of work to better match CodeGen. That
+  // ultimately ends up in setGlobalVisibility, which already has the linkage of
+  // the LLVM GV (corresponding to our FuncOp) computed, so it doesn't have to
+  // recompute it here. This is a minimal fix for now.
+  if (!isLocalLinkage(getFunctionLinkage(globalDecl))) {
+    auto decl = globalDecl.getDecl();
+    func.setGlobalVisibilityAttr(getGlobalVisibilityAttrFromDecl(decl));
+  }
 }
 
 /// If the specified mangled name is not in the module,

clang/test/CIR/CodeGen/visibility-attribute.c

@@ -30,9 +30,24 @@ void __attribute__((__visibility__("protected"))) foo_protected();
 // CIR: cir.func no_proto private protected @foo_protected(...)
 // LLVM: declare {{.*}} protected void @foo_protected(...)
 
+static void static_foo_default() {}
+// CIR: cir.func no_proto internal private @static_foo_default()
+// LLVM: define internal void @static_foo_default()
+
+static void __attribute__((__visibility__("hidden"))) static_foo_hidden() {}
+// CIR: cir.func no_proto internal private @static_foo_hidden()
+// LLVM: define internal void @static_foo_hidden()
+
+static void __attribute__((__visibility__("protected"))) static_foo_protected() {}
+// CIR: cir.func no_proto internal private @static_foo_protected()
+// LLVM: define internal void @static_foo_protected()
+
 void call_foo()
 {
   foo_default();
   foo_hidden();
   foo_protected();
+  static_foo_default();
+  static_foo_hidden();
+  static_foo_protected();
 }