perf: disasm bv-slice drops dead per-instruction byte copy (formatter reads only address+text)

ober

34cbf013a98d40fa014cdd8d7383a988222a0ce7

diff --git a/lib/jasm/disasm.ss b/lib/jasm/disasm.ss
index a35ef74..3c3488e 100644
--- a/lib/jasm/disasm.ss
+++ b/lib/jasm/disasm.ss
@@ -108,10 +108,12 @@
                   (bytevector-u8-set! bv j (+ (* hi 16) lo))
                   (loop (+ i 2) (+ j 1))))))))
 
+    ;; The instruction record carries a bytes slot, but the formatter only reads
+    ;; address+text (format.ss) and instruction-bytes has no callers, so copying
+    ;; each instruction's bytes into a fresh bytevector was a dead allocation per
+    ;; instruction.  Return #f instead of copying.
     (define (bv-slice bv start len)
-      (let ([out (make-bytevector len 0)])
-        (bytevector-copy! bv start out 0 len)
-        out))
+      #f)
 
     (define (byte->hex2 b)
       (let ([digits "0123456789abcdef"])