[Sbcl-devel] Block compilation lives again.

[Charles Z. <cha...@ya...>]

Hi folks,
A heads up that I've checked in block compilation support. I tried hard to make it a no-op, since most of the changes are guarded against actually using the feature, but there is a remote chance it might much something up (I did change the lifetime of the ir1-namespace hashtables and needed to hack around some cross-type ambiguity warnings deriving from some recent changes with another queued tlf mechanism that was recently added). Since as far as I can tell we have never supported it, we also don't have any user facing documentation for the feature. Can we lift the relevant sections of the CMUCL manual directly into our docs?
A big omission is the CMUCL-style START-BLOCK END-BLOCK proclamations which specify the scope of block compilation and their entry points. I didn't want to open this can of worms because apparently it was the reason it was gutted out in the first place (i.e. the non-ANSI conformance of how these proclamations behaved in CMUCL). But the :block-compile and :entry-point keywords should work fine. Are the declarations something we would be interested supporting again, as a non-ANSI extension? I'd be interested in seeing if we can self host the compiler for delivery with it enabled to some extent, like CMUCL does.

The re-implementation isn't perfect and I think source info and inlining may not interact with block compiling correctly., although I *think* compile-file should behave more or less entirely ANSI-compliant with this approach.

Anyway, here is a quick demonstration:
foo.lisp
(defun foo (x y)
  (print (bar x y))
  (bar x y))

(defun bar (x y)
  (+ x y))

(defun fact (n)
  (if (zerop n)
      1
      (* n (fact (1- n)))))

> (compile-file "test.lisp" :block-compile t :entry-points nil)> (load "test.fasl")
(sb-disassem:disassemble-code-component #'foo)
; Size: 210 bytes. Origin: #x52E63F90 (segment 1 of 4)        ; (XEP BAR)
; 3F90:       .ENTRY BAR(X Y)                                 ; (SB-INT:SFUNCTION
                                                              ;  (T T) NUMBER)
; 3FA0:       8F4508           POP QWORD PTR [RBP+8]
; 3FA3:       4883F904         CMP RCX, 4
; 3FA7:       0F85B1000000     JNE L2
; 3FAD:       488D65D0         LEA RSP, [RBP-48]
; 3FB1:       4C8BC2           MOV R8, RDX
; 3FB4:       488BF7           MOV RSI, RDI
; 3FB7:       EB03             JMP L1
; 3FB9: L0:   8F4508           POP QWORD PTR [RBP+8]
; Origin #x52E63FBC (segment 2 of 4)                          ; BAR
; 3FBC: L1:   498B4510         MOV RAX, [R13+16]              ; thread.binding-stack-pointer
; 3FC0:       488945F8         MOV [RBP-8], RAX
; 3FC4:       4C8945D8         MOV [RBP-40], R8
; 3FC8:       488975D0         MOV [RBP-48], RSI
; 3FCC:       498BD0           MOV RDX, R8
; 3FCF:       488BFE           MOV RDI, RSI
; 3FD2:       E8B9CB29FF       CALL #x52100B90                ; GENERIC-+
; 3FD7:       488B75D0         MOV RSI, [RBP-48]
; 3FDB:       4C8B45D8         MOV R8, [RBP-40]
; 3FDF:       488BE5           MOV RSP, RBP
; 3FE2:       F8               CLC
; 3FE3:       5D               POP RBP
; 3FE4:       C3               RET
; Origin #x52E63FE5 (segment 3 of 4)                          ; (XEP FOO)
; 3FE5:       .SKIP 11
; 3FF0:       .ENTRY FOO(X Y)                                 ; (SB-INT:SFUNCTION
                                                              ;  (T T) NUMBER)
; 4000:       8F4508           POP QWORD PTR [RBP+8]
; 4003:       4883F904         CMP RCX, 4
; 4007:       7557             JNE L3
; 4009:       488D65D0         LEA RSP, [RBP-48]
; 400D:       488955E8         MOV [RBP-24], RDX
; 4011:       48897DE0         MOV [RBP-32], RDI
; Origin #x52E64015 (segment 4 of 4)                          ; FOO
; 4015:       498B4510         MOV RAX, [R13+16]              ; thread.binding-stack-pointer
; 4019:       488945F0         MOV [RBP-16], RAX
; 401D:       4C8BCD           MOV R9, RBP
; 4020:       488D4424F0       LEA RAX, [RSP-16]
; 4025:       4883EC40         SUB RSP, 64
; 4029:       4C8B45E8         MOV R8, [RBP-24]
; 402D:       488B75E0         MOV RSI, [RBP-32]
; 4031:       4C8908           MOV [RAX], R9
; 4034:       488BE8           MOV RBP, RAX
; 4037:       E87DFFFFFF       CALL L0
; 403C:       4883EC10         SUB RSP, 16
; 4040:       B902000000       MOV ECX, 2
; 4045:       48892C24         MOV [RSP], RBP
; 4049:       488BEC           MOV RBP, RSP
; 404C:       E8F1E163FD       CALL #x504A2242                ; #<FDEFN PRINT>
; 4051:       4C8B45E8         MOV R8, [RBP-24]
; 4055:       488B75E0         MOV RSI, [RBP-32]
; 4059:       E95EFFFFFF       JMP L1
; 405E: L2:   CC10             INT3 16                        ; Invalid argument count trap
; 4060: L3:   CC10             INT3 16                        ; Invalid argument count trap
FOO and BAR are compiled into the same component (with local calls), and both have valid external entry points.
> (compile-file "test.lisp" :block-compile t :entry-points '(bar fact))
FOO is removed for being unused.
> (compile-file "test.lisp" :block-compile :specified)
FOO, BAR, and FACT get entry points, and FACT calls itself directly and not through an FDEFN.
Cheers.