A problem with jump tables and register spilling

[Stas Boukarev]

(defun foo (x m)
  (declare (optimize (speed 2) (debug 1)))
  (case x
    ((a b c) 1
     (if m
         (error "a")))
    ((d e f)
     (print x)
     32)))

spills X only in the abc branch, but it reads it from the stack in the def branch:

(foo 'd  3)

#<unknown immediate object, lowtag=#b1001, widetag=#x59 {21A45A59}>
32

[Stas Boukarev (stassats)]

It's actually due to SB-C::*do-instcombine-pass*, setting it to NIL I get

; 9EF: 488B75F0 MOV RSI, [RBP-16]
; 9F3: L5: 488975F0 MOV [RBP-16], RSI