Off-by-one (or, type mismatch) error in LOGTEST of fixnums

[Sean Maher]

In the following:

(defstruct bitsy
  (fix 0 :type fixnum))

(defun s62 (x) (logtest (ash 1 62) (bitsy-fix (truly-the bitsy x))))

(s62 (make-bitsy :fix (ash 1 61)))
=> T

The last expression returns T when it should return NIL.

SBCL's version is "SBCL 2.1.5.173.HEAD.1-e36ecc2b4", but I'm not sure why it's tagged 2.1.5, it's one of the most recent commits.

Uname -a: Linux rooty 5.12.14_1 #1 SMP 1625102948 x86_64 GNU/Linux

Features:
(:SWANK :QUICKLISP :ASDF3.3 :ASDF3.2 :ASDF3.1 :ASDF3 :ASDF2 :ASDF :OS-UNIX
 :NON-BASE-CHARS-EXIST-P :ASDF-UNICODE :X86-64 :GENCGC :64-BIT :ANSI-CL
 :COMMON-LISP :ELF :IEEE-FLOATING-POINT :LINUX :LITTLE-ENDIAN
 :PACKAGE-LOCAL-NICKNAMES :SB-CORE-COMPRESSION :SB-DEVEL :SB-LDB
 :SB-PACKAGE-LOCKS :SB-THREAD :SB-UNICODE :SBCL :UNIX)

[Douglas Katzman (dougk)]

The vop combining optimizer got confused which happens only when mixing a (signed-byte 64) operand and a fixnum, and (ash 1 62) exceeds a fixnum, so it has to be (signed-byte 64).