CFI: Use Instance at callsites

We already use `Instance` at declaration sites when available to glean
additional information about possible abstractions of the type in use.
This does the same when possible at callsites as well.

The primary purpose of this change is to allow CFI to alter how it
generates type information for indirect calls through `Virtual`
instances.

compiler/rustc_codegen_ssa/src/traits/builder.rs

@@ -17,7 +17,7 @@ use crate::MemFlags;
 
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
 use rustc_middle::ty::layout::{HasParamEnv, TyAndLayout};
-use rustc_middle::ty::Ty;
+use rustc_middle::ty::{Instance, Ty};
 use rustc_session::config::OptLevel;
 use rustc_span::Span;
 use rustc_target::abi::call::FnAbi;
@@ -82,6 +82,7 @@ pub trait BuilderMethods<'a, 'tcx>:
         then: Self::BasicBlock,
         catch: Self::BasicBlock,
         funclet: Option<&Self::Funclet>,
+        instance: Option<Instance<'tcx>>,
     ) -> Self::Value;
     fn unreachable(&mut self);
 
@@ -389,6 +390,7 @@ pub trait BuilderMethods<'a, 'tcx>:
         llfn: Self::Value,
         args: &[Self::Value],
         funclet: Option<&Self::Funclet>,
+        instance: Option<Instance<'tcx>>,
     ) -> Self::Value;
     fn zext(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;