define location-print-name function

it's not necessary for cross-compilation as such, but I'm spending a
lot of time in the debugger, and the debugger wants to print things,
so at least give the system a chance to print the things.

also support constants in LOCATION-PRINT-NAME, because a named
call (such as to %CHECK-BOUND) needs a constant location.  The fact
that we shouldn't have a named call to %CHECK-BOUND is, well, a
symptom of our incremental backend development

src/compiler/rv32/vm.lisp

@@ -112,5 +112,15 @@
 (defconstant lra-save-offset 1)
 (defconstant nfp-save-offset 2)
 
+(defun location-print-name (tn)
+  (declare (type tn tn))
+  (let ((sb (sb-name (sc-sb (tn-sc tn))))
+        (offset (tn-offset tn)))
+    (ecase sb
+      (registers (or (svref *register-names* offset)
+                     (format nil "x~D" offset)))
+      (float-registers (format nil "f~D" offset))
+      (constant (format nil "Const~D" offset)))))
+
 (defun combination-implementation-style (node)
   (values :default nil))