CFI: Switch sense of type erasure flag

Previously, we had `NO_SELF_TYPE_ERASURE`, a negative configuration. Now
we have `ERASE_SELF_TYPE`, a positive configuration.

Author: maurer

compiler/rustc_codegen_llvm/src/declare.rs

@@ -147,7 +147,7 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
                 for options in [
                     TypeIdOptions::GENERALIZE_POINTERS,
                     TypeIdOptions::NORMALIZE_INTEGERS,
-                    TypeIdOptions::NO_SELF_TYPE_ERASURE,
+                    TypeIdOptions::ERASE_SELF_TYPE,
                 ]
                 .into_iter()
                 .powerset()
@@ -173,7 +173,9 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
 
         if self.tcx.sess.is_sanitizer_kcfi_enabled() {
             // LLVM KCFI does not support multiple !kcfi_type attachments
-            let mut options = TypeIdOptions::empty();
+            // Default to erasing the self type. If we need the concrete type, there will be a
+            // hint in the instance.
+            let mut options = TypeIdOptions::ERASE_SELF_TYPE;
             if self.tcx.sess.is_sanitizer_cfi_generalize_pointers_enabled() {
                 options.insert(TypeIdOptions::GENERALIZE_POINTERS);
             }

compiler/rustc_symbol_mangling/src/typeid.rs

@@ -24,9 +24,9 @@ bitflags! {
         /// `-fsanitize-cfi-icall-experimental-normalize-integers` option for cross-language LLVM
         /// CFI and  KCFI support.
         const NORMALIZE_INTEGERS = 4;
-        /// Do not perform self type erasure for attaching a secondary type id to methods with their
-        /// concrete self so they can be used as function pointers.
-        const NO_SELF_TYPE_ERASURE = 8;
+        /// Generalize the instance by erasing the concrete `Self` type where possible.
+        /// Only has an effect on `{kcfi_,}typeid_for_instance`.
+        const ERASE_SELF_TYPE = 8;
     }
 }
 

compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs

@@ -1172,7 +1172,7 @@ pub fn typeid_for_instance<'tcx>(
         instance.args = tcx.mk_args_trait(invoke_ty, trait_ref.args.into_iter().skip(1));
     }
 
-    if !options.contains(EncodeTyOptions::NO_SELF_TYPE_ERASURE) {
+    if options.contains(EncodeTyOptions::ERASE_SELF_TYPE) {
         if let Some(impl_id) = tcx.impl_of_method(instance.def_id())
             && let Some(trait_ref) = tcx.impl_trait_ref(impl_id)
         {

tests/codegen/sanitizer/cfi/emit-type-metadata-id-itanium-cxx-abi-method-secondary-typeid.rs

@@ -18,5 +18,5 @@ impl Trait1 for Type1 {
 }
 
 
-// CHECK: ![[TYPE1]] = !{i64 0, !"_ZTSFvu3refIu3dynIu{{[0-9]+}}NtC{{[[:print:]]+}}_{{[[:print:]]+}}6Trait1u6regionEEE"}
-// CHECK: ![[TYPE2]] = !{i64 0, !"_ZTSFvu3refIu{{[0-9]+}}NtC{{[[:print:]]+}}_{{[[:print:]]+}}5Type1EE"}
+// CHECK: ![[TYPE1]] = !{i64 0, !"_ZTSFvu3refIu{{[0-9]+}}NtC{{[[:print:]]+}}_{{[[:print:]]+}}5Type1EE"}
+// CHECK: ![[TYPE2]] = !{i64 0, !"_ZTSFvu3refIu3dynIu{{[0-9]+}}NtC{{[[:print:]]+}}_{{[[:print:]]+}}6Trait1u6regionEEE"}