compiler.cfg.ssa.destruction: we can coalesce two registers with different representations as long as they both belong to the same register class

basis/compiler/cfg/ssa/destruction/destruction.factor

@@ -3,6 +3,7 @@
 USING: accessors arrays assocs fry kernel namespaces
 sequences sequences.deep
 sets vectors
+cpu.architecture
 compiler.cfg.rpo
 compiler.cfg.def-use
 compiler.cfg.renaming
@@ -67,7 +68,7 @@ M: insn prepare-insn
     [ defs-vreg ] [ uses-vregs ] bi
     2dup empty? not and [
         first 
-        2dup [ rep-of ] bi@ eq?
+        2dup [ rep-of reg-class-of ] bi@ eq?
         [ try-to-coalesce ] [ 2drop ] if
     ] [ 2drop ] if ;