interpret: call caller_location logic the same way codegen does, and share some code

Author: RalfJung

src/common.rs

@@ -433,16 +433,7 @@ impl<'tcx> FunctionCx<'_, '_, 'tcx> {
     // Note: must be kept in sync with get_caller_location from cg_ssa
     pub(crate) fn get_caller_location(&mut self, mut source_info: mir::SourceInfo) -> CValue<'tcx> {
         let span_to_caller_location = |fx: &mut FunctionCx<'_, '_, 'tcx>, span: Span| {
-            use rustc_session::RemapFileNameExt;
-            let topmost = span.ctxt().outer_expn().expansion_cause().unwrap_or(span);
-            let caller = fx.tcx.sess.source_map().lookup_char_pos(topmost.lo());
-            let const_loc = fx.tcx.const_caller_location((
-                rustc_span::symbol::Symbol::intern(
-                    &caller.file.name.for_codegen(&fx.tcx.sess).to_string_lossy(),
-                ),
-                caller.line as u32,
-                caller.col_display as u32 + 1,
-            ));
+            let const_loc = fx.tcx.span_as_caller_location(span);
             crate::constant::codegen_const_value(fx, const_loc, fx.tcx.caller_location_ty())
         };