Re: Shrinking the C core

["Alfred M. Szmidt" <ams@gnu.org>]

Please keep the CC intact, not everyone subscribed.

   > It should be quite obvious why SBCL is faster than the Emacs
   > Lisp VM (or even native). Just look at this call to (car
   > "foo"), and compare what happens in Emacs.
   >
   > * (disassemble 'foo)
   > ; disassembly for FOO
   > ; Size: 166 bytes. Origin: #x225D873F                         ; FOO
   > ; 3F:       488B042590060020 MOV RAX, [#x20000690]
   > ; 47:       488945F8         MOV [RBP-8], RAX
   > ; 4B:       48892C2560060020 MOV [#x20000660], RBP
   > ; 53:       488B142518000020 MOV RDX, [#x20000018]
   > ; 5B:       488D4210         LEA RAX, [RDX+16]
   > ; 5F:       483B042520000020 CMP RAX, [#x20000020]
   > ; 67:       7770             JA L2
   > ; 69:       4889042518000020 MOV [#x20000018], RAX
   > ; 71: L0:   488B0570FFFFFF   MOV RAX, [RIP-144]               ; "foo"
   > ; 78:       488902           MOV [RDX], RAX
   > ; 7B:       48C7420817010020 MOV QWORD PTR [RDX+8], #x20000117  ; NIL
   > ; 83:       80CA07           OR DL, 7
   > ; 86:       48312C2560060020 XOR [#x20000660], RBP
   > ; 8E:       7402             JEQ L1
   > ; 90:       CC09             INT3 9                           ; pending interrupt trap
   > ; 92: L1:   4C8D4424F0       LEA R8, [RSP-16]
   > ; 97:       4883EC30         SUB RSP, 48
   > ; 9B:       BFAF0B1520       MOV EDI, #x20150BAF              ; 'LIST
   > ; A0:       488B3551FFFFFF   MOV RSI, [RIP-175]               ; '(VALUES
   >                                                               ;   (SIMPLE-ARRAY ..))
   > ; A7:       488B0552FFFFFF   MOV RAX, [RIP-174]               ; '("foo")
   > ; AE:       498940F0         MOV [R8-16], RAX
   > ; B2:       488B054FFFFFFF   MOV RAX, [RIP-177]               ; "(CAR \"foo\")"
   > ; B9:       498940E8         MOV [R8-24], RAX
   > ; BD:       49C740E017010020 MOV QWORD PTR [R8-32], #x20000117  ; NIL
   > ; C5:       B90C000000       MOV ECX, 12
   > ; CA:       498928           MOV [R8], RBP
   > ; CD:       498BE8           MOV RBP, R8
   > ; D0:       B882B12620       MOV EAX, #x2026B182              ; #<FDEFN SB-C::%COMPILE-TIME-TYPE-ERROR>
   > ; D5:       FFD0             CALL RAX
   > ; D7:       CC10             INT3 16                          ; Invalid argument count trap
   > ; D9: L2:   6A10             PUSH 16
   > ; DB:       FF1425B0080020   CALL [#x200008B0]                ; #x21A00540: LIST-ALLOC-TRAMP
   > ; E2:       5A               POP RDX
   > ; E3:       EB8C             JMP L0
   > NIL
   > * 

   Okay?

I guess that you do not understand the above?  Or what?  Do you know
and understand what happens in Emacs when a similar call is done?  It
is far more than "166 bytes".

   >> If we talk about type checking, Elisp uses dynamic typing
   >> and compilation cannot do much about it. Native compilation
   >> also does not touch C subroutines - the place where
   >> typechecks are performed.
   >
   > SBCL implements a Lisp, Lisp by definition is
   > dynamically typed.

   Only for the kind of use (code) that we are used to. See this:

     https://medium.com/@MartinCracauer/static-type-checking-in-the-programmable-programming-language-lisp-79bb79eb068a

This has literally nothing to do with the difference between static
typing, and dynamic typing.  The author, and you, have it completeley
backwards to the point where I need to suggest that you take sometime
to read up on basic Lisp compilers, and then look into very good Lisp
compilers (CMUCL and SBCL come to mind).  Since it is already showing
that it is very hard to even explain basic Lisp compiler behaviour
without going to fundamentals.