fix(sb-simd): define missing-instruction fallbacks for sap-ref on unsupported CPUs

- In define-vrefs.lisp, emit define-missing-instruction forms for ,sap
  and (setf ,sap) when the target instruction set is not available.
  Prevents unattached definition errors during package validation
  (e.g. F64.8-SAP-REF on hosts without AVX-512 support).
- In missing-instruction.lisp, use record-instruction-set and
  record-name rather than instruction-record-* aliases so that
  missing-instruction error reporting works for sap-ref and other
  function records inheriting from base record.
- Verified under Intel SDE Haswell (-hsw) and Skylake (-skl) emulation
  with 0 errors (737 tests, 9,992,078 checks passed).
- Verified natively on Zen 4 host with 0 regressions (737 tests,
  13,860,908 checks passed).

contrib/sb-simd/code/define-vrefs.lisp

@@ -18,8 +18,12 @@
            (ecase kind
              (:load
               (if (not (instruction-set-available-p instruction-set))
-                  `(define-missing-instruction ,name
-                     :required-arguments (array index))
+                  `(progn
+                     (define-missing-instruction ,name
+                       :required-arguments (array index))
+                     ,@(when sap
+                         `((define-missing-instruction ,sap
+                             :required-arguments (sap index)))))
                   `(progn
                     (define-inline ,name (array index)
                        (declare (type (array ,element-type) array)
@@ -35,8 +39,12 @@
                             (,sap-vop sap index 0)))))))
              (:store
               (if (not (instruction-set-available-p instruction-set))
-                  `(define-missing-instruction ,name
-                     :required-arguments (value array index))
+                  `(progn
+                     (define-missing-instruction ,name
+                       :required-arguments (value array index))
+                     ,@(when sap
+                         `((define-missing-instruction (setf ,sap)
+                             :required-arguments (value sap index)))))
                   `(progn
                     (define-inline ,name (value array index)
                        (declare (type (array ,element-type) array)

contrib/sb-simd/code/missing-instruction.lisp

@@ -11,8 +11,8 @@
     :reader missing-instruction-record))
   (:report
    (lambda (c s)
-     (with-accessors ((instruction-set instruction-record-instruction-set)
-                      (instruction-name instruction-record-name))
+     (with-accessors ((instruction-set record-instruction-set)
+                      (instruction-name record-name))
          (missing-instruction-record c)
        (format s "Missing ~S instruction ~S."
                (instruction-set-name instruction-set)

src/compiler/x86-64/avx2-insts.lisp

@@ -438,8 +438,8 @@
       (#x0F   #b001)
       (#x0F38 #b010)
       (#x0F3A #b011)
-      ((:map5 5 #x5) #b101)
-      ((:map6 6 #x6) #b110))))
+      ((:map5 5) #b101)
+      ((:map6 6) #b110))))
 
 (defun emit-two-byte-vex (segment r vvvv l pp)
   (emit-bytes segment