X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcompiler%2Fx86%2Fmacros.lisp;h=a054404313494d0b64995d12069b31bd38dd8e38;hb=8902b8b6bd2e9285749dd39d313b33b6c69c5213;hp=5d4238f04c8cacf22f3804a999c97f114fff49e0;hpb=3c65762b927af861c9c8bc416e4cbac9a14ec0c3;p=sbcl.git diff --git a/src/compiler/x86/macros.lisp b/src/compiler/x86/macros.lisp index 5d4238f..a054404 100644 --- a/src/compiler/x86/macros.lisp +++ b/src/compiler/x86/macros.lisp @@ -11,12 +11,12 @@ (in-package "SB!VM") -;;; We can load/store into fp registers through the top of -;;; stack %st(0) (fr0 here). Loads imply a push to an empty register -;;; which then changes all the reg numbers. These macros help manage that. +;;; We can load/store into fp registers through the top of stack +;;; %st(0) (fr0 here). Loads imply a push to an empty register which +;;; then changes all the reg numbers. These macros help manage that. -;;; Use this when we don't have to load anything. It preserves old tos value, -;;; but probably destroys tn with operation. +;;; Use this when we don't have to load anything. It preserves old tos +;;; value, but probably destroys tn with operation. (defmacro with-tn@fp-top((tn) &body body) `(progn (unless (zerop (tn-offset ,tn)) @@ -47,7 +47,7 @@ (inst mov ,n-dst ,n-src)))) (defmacro make-ea-for-object-slot (ptr slot lowtag) - `(make-ea :dword :base ,ptr :disp (- (* ,slot word-bytes) ,lowtag))) + `(make-ea :dword :base ,ptr :disp (- (* ,slot n-word-bytes) ,lowtag))) (defmacro loadw (value ptr &optional (slot 0) (lowtag 0)) `(inst mov ,value (make-ea-for-object-slot ,ptr ,slot ,lowtag))) @@ -84,7 +84,36 @@ (- other-pointer-lowtag))) ,reg)) - +#!+sb-thread +(defmacro load-tl-symbol-value (reg symbol) + `(progn + (inst mov ,reg + (make-ea :dword + :disp (+ nil-value + (static-symbol-offset ',symbol) + (ash symbol-tls-index-slot word-shift) + (- other-pointer-lowtag)))) + (inst fs-segment-prefix) + (inst mov ,reg (make-ea :dword :scale 1 :index ,reg)))) +#!-sb-thread +(defmacro load-tl-symbol-value (reg symbol) `(load-symbol-value ,reg ,symbol)) + +#!+sb-thread +(defmacro store-tl-symbol-value (reg symbol temp) + `(progn + (inst mov ,temp + (make-ea :dword + :disp (+ nil-value + (static-symbol-offset ',symbol) + (ash symbol-tls-index-slot word-shift) + (- other-pointer-lowtag)))) + (inst fs-segment-prefix) + (inst mov (make-ea :dword :scale 1 :index ,temp) ,reg))) +#!-sb-thread +(defmacro store-tl-symbol-value (reg symbol temp) + (declare (ignore temp)) + `(store-symbol-value ,reg ,symbol)) + (defmacro load-type (target source &optional (offset 0)) #!+sb-doc "Loads the type bits of a pointer into target independent of @@ -102,159 +131,112 @@ ;;;; allocation helpers -;;; Two allocation approaches are implemented. A call into C can be -;;; used, and in that case special care can be taken to disable -;;; interrupts. Alternatively with gencgc inline allocation is possible -;;; although it isn't interrupt safe. +;;; All allocation is done by calls to assembler routines that +;;; eventually invoke the C alloc() function. Once upon a time +;;; (before threads) allocation within an alloc_region could also be +;;; done inline, with the aid of two C symbols storing the current +;;; allocation region boundaries; however, C symbols are global. + +;;; C calls for allocation don't /seem/ to make an awful lot of +;;; difference to speed. Guessing from historical context, it looks +;;; like inline allocation was introduced before pseudo-atomic, at +;;; which time all calls to alloc() would have needed a syscall to +;;; mask signals for the duration. Now we have pseudoatomic there's +;;; no need for that overhead. Still, inline alloc would be a neat +;;; addition someday (except see below). + +(defun allocation-dynamic-extent (alloc-tn size) + (inst sub esp-tn size) + ;; FIXME: SIZE _should_ be double-word aligned (suggested but + ;; unfortunately not enforced by PAD-DATA-BLOCK and + ;; WITH-FIXED-ALLOCATION), so that ESP is always divisible by 8 (for + ;; 32-bit lispobjs). In that case, this AND instruction is + ;; unneccessary and could be removed. If not, explain why. -- CSR, + ;; 2004-03-30 + (inst and esp-tn #.(ldb (byte 32 0) (lognot lowtag-mask))) + (aver (not (location= alloc-tn esp-tn))) + (inst mov alloc-tn esp-tn) + (values)) + +(defun allocation-notinline (alloc-tn size) + (let* ((alloc-tn-offset (tn-offset alloc-tn)) + ;; C call to allocate via dispatch routines. Each + ;; destination has a special entry point. The size may be a + ;; register or a constant. + (tn-text (ecase alloc-tn-offset + (#.eax-offset "eax") + (#.ecx-offset "ecx") + (#.edx-offset "edx") + (#.ebx-offset "ebx") + (#.esi-offset "esi") + (#.edi-offset "edi"))) + (size-text (case size (8 "8_") (16 "16_") (t "")))) + (unless (or (eql size 8) (eql size 16)) + (unless (and (tn-p size) (location= alloc-tn size)) + (inst mov alloc-tn size))) + (inst call (make-fixup (extern-alien-name + (concatenate 'string + "alloc_" size-text + "to_" tn-text)) + :foreign)))) + +(defun allocation-inline (alloc-tn size) + (let ((ok (gen-label)) + (free-pointer + (make-ea :dword :disp + #!+sb-thread (* n-word-bytes thread-alloc-region-slot) + #!-sb-thread (make-fixup (extern-alien-name "boxed_region") + :foreign) + :scale 1)) ; thread->alloc_region.free_pointer + (end-addr + (make-ea :dword :disp + #!+sb-thread (* n-word-bytes (1+ thread-alloc-region-slot)) + #!-sb-thread (make-fixup (extern-alien-name "boxed_region") + :foreign 4) + :scale 1))) ; thread->alloc_region.end_addr + (unless (and (tn-p size) (location= alloc-tn size)) + (inst mov alloc-tn size)) + #!+sb-thread (inst fs-segment-prefix) + (inst add alloc-tn free-pointer) + #!+sb-thread (inst fs-segment-prefix) + (inst cmp alloc-tn end-addr) + (inst jmp :be OK) + (let ((dst (ecase (tn-offset alloc-tn) + (#.eax-offset "alloc_overflow_eax") + (#.ecx-offset "alloc_overflow_ecx") + (#.edx-offset "alloc_overflow_edx") + (#.ebx-offset "alloc_overflow_ebx") + (#.esi-offset "alloc_overflow_esi") + (#.edi-offset "alloc_overflow_edi")))) + (inst call (make-fixup (extern-alien-name dst) :foreign))) + (emit-label ok) + #!+sb-thread (inst fs-segment-prefix) + (inst xchg free-pointer alloc-tn)) + (values)) -;;; For GENCGC it is possible to inline object allocation, to permit -;;; this set the following variable to True. -;;; -;;; FIXME: The comment above says that this isn't interrupt safe. Is that -;;; right? If so, do we want to do this? And surely we don't want to do this by -;;; default? How much time does it save to do this? Is it any different in the -;;; current CMU CL version instead of the one that I grabbed in 1998? -;;; (Later observation: In order to be interrupt safe, it'd probably -;;; have to use PSEUDO-ATOMIC, so it's probably not -- yuck. Try benchmarks -;;; with and without inline allocation, and unless the inline allocation -;;; wins by a whole lot, it's not likely to be worth messing with. If -;;; we want to hack up memory allocation for performance, effort spent -;;; on DYNAMIC-EXTENT would probably give a better payoff.) -(defvar *maybe-use-inline-allocation* t) ;;; Emit code to allocate an object with a size in bytes given by -;;; Size. The size may be an integer of a TN. If Inline is a VOP +;;; SIZE. The size may be an integer or a TN. If Inline is a VOP ;;; node-var then it is used to make an appropriate speed vs size ;;; decision. -;;; -;;; FIXME: We call into C.. except when inline allocation is enabled..? -;;; -;;; FIXME: Also, calls to -;;; ALLOCATION are always wrapped with PSEUDO-ATOMIC -- why? Is it to -;;; make sure that no GC happens between the time of allocation and the -;;; time that the allocated memory has its tag bits set correctly? -;;; If so, then ALLOCATION itself might as well set the PSEUDO-ATOMIC -;;; bits, so that the caller need only clear them. Check whether it's -;;; true that every ALLOCATION is surrounded by PSEUDO-ATOMIC, and -;;; that every PSEUDO-ATOMIC contains a single ALLOCATION, which is -;;; its first instruction. If so, the connection should probably be -;;; formalized, in documentation and in macro definition, -;;; with the macro becoming e.g. PSEUDO-ATOMIC-ALLOCATION. -(defun allocation (alloc-tn size &optional inline) - (flet ((load-size (dst-tn size) - (unless (and (tn-p size) (location= alloc-tn size)) - (inst mov dst-tn size)))) - (let ((alloc-tn-offset (tn-offset alloc-tn))) - ;; FIXME: All these (MAKE-FIXUP (EXTERN-ALIEN-NAME "foo") :FOREIGN) - ;; expressions should be moved into MACROLET ((ALIEN-FIXUP ..)), - ;; and INST CALL (MAKE-FIXUP ..) should become CALL-ALIEN-FIXUP. - (if (and #!+gencgc t #!-gencgc nil - *maybe-use-inline-allocation* - (or (null inline) (policy inline (>= speed space)))) - ;; Inline allocation with GENCGC. - (let ((ok (gen-label))) - ;; Load the size first so that the size can be in the same - ;; register as alloc-tn. - (load-size alloc-tn size) - (inst add alloc-tn - (make-fixup (extern-alien-name "current_region_free_pointer") - :foreign)) - (inst cmp alloc-tn - (make-fixup (extern-alien-name "current_region_end_addr") - :foreign)) - (inst jmp :be OK) - ;; Dispatch to the appropriate overflow routine. There is a - ;; routine for each destination. - ;; FIXME: Could we use an alist here instead of an ECASE with lots - ;; of duplicate code? (and similar question for next ECASE, too) - (ecase alloc-tn-offset - (#.eax-offset ;; FIXME: Why the #\# #\.? - (inst call (make-fixup (extern-alien-name "alloc_overflow_eax") - :foreign))) - (#.ecx-offset - (inst call (make-fixup (extern-alien-name "alloc_overflow_ecx") - :foreign))) - (#.edx-offset - (inst call (make-fixup (extern-alien-name "alloc_overflow_edx") - :foreign))) - (#.ebx-offset - (inst call (make-fixup (extern-alien-name "alloc_overflow_ebx") - :foreign))) - (#.esi-offset - (inst call (make-fixup (extern-alien-name "alloc_overflow_esi") - :foreign))) - (#.edi-offset - (inst call (make-fixup (extern-alien-name "alloc_overflow_edi") - :foreign)))) - (emit-label ok) - (inst xchg (make-fixup - (extern-alien-name "current_region_free_pointer") - :foreign) - alloc-tn)) - ;; C call to allocate via dispatch routines. Each - ;; destination has a special entry point. The size may be a - ;; register or a constant. - (ecase alloc-tn-offset - (#.eax-offset - (case size - (8 (inst call (make-fixup (extern-alien-name "alloc_8_to_eax") - :foreign))) - (16 (inst call (make-fixup (extern-alien-name "alloc_16_to_eax") - :foreign))) - (t - (load-size eax-tn size) - (inst call (make-fixup (extern-alien-name "alloc_to_eax") - :foreign))))) - (#.ecx-offset - (case size - (8 (inst call (make-fixup (extern-alien-name "alloc_8_to_ecx") - :foreign))) - (16 (inst call (make-fixup (extern-alien-name "alloc_16_to_ecx") - :foreign))) - (t - (load-size ecx-tn size) - (inst call (make-fixup (extern-alien-name "alloc_to_ecx") - :foreign))))) - (#.edx-offset - (case size - (8 (inst call (make-fixup (extern-alien-name "alloc_8_to_edx") - :foreign))) - (16 (inst call (make-fixup (extern-alien-name "alloc_16_to_edx") - :foreign))) - (t - (load-size edx-tn size) - (inst call (make-fixup (extern-alien-name "alloc_to_edx") - :foreign))))) - (#.ebx-offset - (case size - (8 (inst call (make-fixup (extern-alien-name "alloc_8_to_ebx") - :foreign))) - (16 (inst call (make-fixup (extern-alien-name "alloc_16_to_ebx") - :foreign))) - (t - (load-size ebx-tn size) - (inst call (make-fixup (extern-alien-name "alloc_to_ebx") - :foreign))))) - (#.esi-offset - (case size - (8 (inst call (make-fixup (extern-alien-name "alloc_8_to_esi") - :foreign))) - (16 (inst call (make-fixup (extern-alien-name "alloc_16_to_esi") - :foreign))) - (t - (load-size esi-tn size) - (inst call (make-fixup (extern-alien-name "alloc_to_esi") - :foreign))))) - (#.edi-offset - (case size - (8 (inst call (make-fixup (extern-alien-name "alloc_8_to_edi") - :foreign))) - (16 (inst call (make-fixup (extern-alien-name "alloc_16_to_edi") - :foreign))) - (t - (load-size edi-tn size) - (inst call (make-fixup (extern-alien-name "alloc_to_edi") - :foreign))))))))) + +;;; Allocation should only be used inside a pseudo-atomic section, which +;;; should also cover subsequent initialization of the object. + +;;; (FIXME: so why aren't we asserting this?) + +(defun allocation (alloc-tn size &optional inline dynamic-extent) + (cond + (dynamic-extent (allocation-dynamic-extent alloc-tn size)) + ;; FIXME: for reasons unknown, inline allocation is a speed win on + ;; non-P4s, and a speed loss on P4s (and probably other such + ;; high-spec high-cache machines). :INLINE-ALLOCATION-IS-GOOD is + ;; a bit of a KLUDGE, really. -- CSR, 2004-08-05 (following + ;; observations made by ASF and Juho Snellman) + ((and (member :inline-allocation-is-good *backend-subfeatures*) + (or (null inline) (policy inline (>= speed space)))) + (allocation-inline alloc-tn size)) + (t (allocation-notinline alloc-tn size))) (values)) ;;; Allocate an other-pointer object of fixed SIZE with a single word @@ -264,29 +246,14 @@ &rest forms) `(pseudo-atomic (allocation ,result-tn (pad-data-block ,size) ,inline) - (storew (logior (ash (1- ,size) sb!vm:n-widetag-bits) ,widetag) + (storew (logior (ash (1- ,size) n-widetag-bits) ,widetag) ,result-tn) (inst lea ,result-tn (make-ea :byte :base ,result-tn :disp other-pointer-lowtag)) ,@forms)) ;;;; error code - -(defvar *adjustable-vectors* nil) - -(defmacro with-adjustable-vector ((var) &rest body) - `(let ((,var (or (pop *adjustable-vectors*) - (make-array 16 - :element-type '(unsigned-byte 8) - :fill-pointer 0 - :adjustable t)))) - (setf (fill-pointer ,var) 0) - (unwind-protect - (progn - ,@body) - (push ,var *adjustable-vectors*)))) - -(eval-when (:compile-toplevel :load-toplevel :execute) +(eval-when (#-sb-xc :compile-toplevel :load-toplevel :execute) (defun emit-error-break (vop kind code values) (let ((vector (gensym))) `((inst int 3) ; i386 breakpoint instruction @@ -318,17 +285,6 @@ (cons 'progn (emit-error-break vop error-trap error-code values))) -;;; not used in SBCL -#| -(defmacro cerror-call (vop label error-code &rest values) - #!+sb-doc - "Cause a continuable error. If the error is continued, execution resumes - at LABEL." - `(progn - ,@(emit-error-break vop cerror-trap error-code values) - (inst jmp ,label))) -|# - (defmacro generate-error-code (vop error-code &rest values) #!+sb-doc "Generate-Error-Code Error-code Value* @@ -339,85 +295,96 @@ (error-call ,vop ,error-code ,@values) start-lab))) -;;; not used in SBCL -#| -(defmacro generate-cerror-code (vop error-code &rest values) - #!+sb-doc - "Generate-CError-Code Error-code Value* - Emit code for a continuable error with the specified Error-Code and - context Values. If the error is continued, execution resumes after - the GENERATE-CERROR-CODE form." - (let ((continue (gensym "CONTINUE-LABEL-")) - (error (gensym "ERROR-LABEL-"))) - `(let ((,continue (gen-label)) - (,error (gen-label))) - (emit-label ,continue) - (assemble (*elsewhere*) - (emit-label ,error) - (cerror-call ,vop ,continue ,error-code ,@values)) - ,error))) -|# ;;;; PSEUDO-ATOMIC -;;; FIXME: This should be a compile-time option, not a runtime option. Doing it -;;; at runtime is bizarre. As I understand it, the default should definitely be -;;; to have pseudo-atomic behavior, but for a performance-critical program -;;; which is guaranteed not to have asynchronous exceptions, it could be worth -;;; something to compile with :SB-NO-PSEUDO-ATOMIC. -(defvar *enable-pseudo-atomic* t) +;;; This is used to wrap operations which leave untagged memory lying +;;; around. It's an operation which the AOP weenies would describe as +;;; having "cross-cutting concerns", meaning it appears all over the +;;; place and there's no logical single place to attach documentation. +;;; grep (mostly in src/runtime) is your friend ;;; FIXME: *PSEUDO-ATOMIC-FOO* could be made into *PSEUDO-ATOMIC-BITS*, ;;; set with a single operation and cleared with SHR *PSEUDO-ATOMIC-BITS*,-2; ;;; the ATOMIC bit is bit 0, the INTERRUPTED bit is bit 1, and you check ;;; the C flag after the shift to see whether you were interrupted. - -;;; FIXME: It appears that PSEUDO-ATOMIC is used to wrap operations which leave -;;; untagged memory lying around, but some documentation would be nice. +;;; +;;; KLUDGE: since the stack on the x86 is treated conservatively, it +;;; does not matter whether a signal occurs during construction of a +;;; dynamic-extent object, as the half-finished construction of the +;;; object will not cause any difficulty. We can therefore elide +(defmacro maybe-pseudo-atomic (really-p &body forms) + `(if ,really-p + (progn ,@forms) + (pseudo-atomic ,@forms))) + +#!+sb-thread +(defmacro pseudo-atomic (&rest forms) + (with-unique-names (label) + `(let ((,label (gen-label))) + (inst fs-segment-prefix) + (inst mov (make-ea :byte + :disp (* 4 thread-pseudo-atomic-interrupted-slot)) 0) + (inst fs-segment-prefix) + (inst mov (make-ea :byte :disp (* 4 thread-pseudo-atomic-atomic-slot)) 1) + ,@forms + (inst fs-segment-prefix) + (inst mov (make-ea :byte :disp (* 4 thread-pseudo-atomic-atomic-slot)) 0) + (inst fs-segment-prefix) + (inst cmp (make-ea :byte + :disp (* 4 thread-pseudo-atomic-interrupted-slot)) 0) + (inst jmp :eq ,label) + ;; if PAI was set, interrupts were disabled at the same + ;; time using the process signal mask. + (inst break pending-interrupt-trap) + (emit-label ,label)))) + +#!-sb-thread (defmacro pseudo-atomic (&rest forms) - (let ((label (gensym "LABEL-"))) + (with-unique-names (label) `(let ((,label (gen-label))) - (when *enable-pseudo-atomic* - ;; FIXME: The MAKE-EA noise should become a MACROLET macro or - ;; something. (perhaps SVLB, for static variable low byte) - (inst mov (make-ea :byte :disp (+ nil-value - (static-symbol-offset - '*pseudo-atomic-interrupted*) - (ash symbol-value-slot word-shift) - ;; FIXME: Use mask, not minus, to - ;; take out type bits. - (- other-pointer-lowtag))) - 0) - (inst mov (make-ea :byte :disp (+ nil-value - (static-symbol-offset - '*pseudo-atomic-atomic*) - (ash symbol-value-slot word-shift) - (- other-pointer-lowtag))) - (fixnumize 1))) + ;; FIXME: The MAKE-EA noise should become a MACROLET macro + ;; or something. (perhaps SVLB, for static variable low + ;; byte) + (inst mov (make-ea :byte :disp (+ nil-value + (static-symbol-offset + '*pseudo-atomic-interrupted*) + (ash symbol-value-slot word-shift) + ;; FIXME: Use mask, not minus, to + ;; take out type bits. + (- other-pointer-lowtag))) + 0) + (inst mov (make-ea :byte :disp (+ nil-value + (static-symbol-offset + '*pseudo-atomic-atomic*) + (ash symbol-value-slot word-shift) + (- other-pointer-lowtag))) + (fixnumize 1)) ,@forms - (when *enable-pseudo-atomic* - (inst mov (make-ea :byte :disp (+ nil-value - (static-symbol-offset - '*pseudo-atomic-atomic*) - (ash symbol-value-slot word-shift) - (- other-pointer-lowtag))) - 0) - ;; KLUDGE: Is there any requirement for interrupts to be - ;; handled in order? It seems as though an interrupt coming - ;; in at this point will be executed before any pending interrupts. - ;; Or do incoming interrupts check to see whether any interrupts - ;; are pending? I wish I could find the documentation for - ;; pseudo-atomics.. -- WHN 19991130 - (inst cmp (make-ea :byte - :disp (+ nil-value - (static-symbol-offset - '*pseudo-atomic-interrupted*) - (ash symbol-value-slot word-shift) - (- other-pointer-lowtag))) - 0) - (inst jmp :eq ,label) - (inst break pending-interrupt-trap) - (emit-label ,label))))) + (inst mov (make-ea :byte :disp (+ nil-value + (static-symbol-offset + '*pseudo-atomic-atomic*) + (ash symbol-value-slot word-shift) + (- other-pointer-lowtag))) + 0) + ;; KLUDGE: Is there any requirement for interrupts to be + ;; handled in order? It seems as though an interrupt coming + ;; in at this point will be executed before any pending + ;; interrupts. Or do incoming interrupts check to see + ;; whether any interrupts are pending? I wish I could find + ;; the documentation for pseudo-atomics.. -- WHN 19991130 + (inst cmp (make-ea :byte + :disp (+ nil-value + (static-symbol-offset + '*pseudo-atomic-interrupted*) + (ash symbol-value-slot word-shift) + (- other-pointer-lowtag))) + 0) + (inst jmp :eq ,label) + ;; if PAI was set, interrupts were disabled at the same + ;; time using the process signal mask. + (inst break pending-interrupt-trap) + (emit-label ,label)))) ;;;; indexed references @@ -434,7 +401,8 @@ (:result-types ,el-type) (:generator 3 ; pw was 5 (inst mov value (make-ea :dword :base object :index index - :disp (- (* ,offset word-bytes) ,lowtag))))) + :disp (- (* ,offset n-word-bytes) + ,lowtag))))) (define-vop (,(symbolicate name "-C")) ,@(when translate `((:translate ,translate))) @@ -446,7 +414,7 @@ (:result-types ,el-type) (:generator 2 ; pw was 5 (inst mov value (make-ea :dword :base object - :disp (- (* (+ ,offset index) word-bytes) + :disp (- (* (+ ,offset index) n-word-bytes) ,lowtag))))))) (defmacro define-full-setter (name type offset lowtag scs el-type &optional translate) @@ -463,7 +431,7 @@ (:result-types ,el-type) (:generator 4 ; was 5 (inst mov (make-ea :dword :base object :index index - :disp (- (* ,offset word-bytes) ,lowtag)) + :disp (- (* ,offset n-word-bytes) ,lowtag)) value) (move result value))) (define-vop (,(symbolicate name "-C")) @@ -478,7 +446,26 @@ (:result-types ,el-type) (:generator 3 ; was 5 (inst mov (make-ea :dword :base object - :disp (- (* (+ ,offset index) word-bytes) ,lowtag)) + :disp (- (* (+ ,offset index) n-word-bytes) + ,lowtag)) value) (move result value))))) +;;; helper for alien stuff. +(defmacro with-pinned-objects ((&rest objects) &body body) + "Arrange with the garbage collector that the pages occupied by +OBJECTS will not be moved in memory for the duration of BODY. +Useful for e.g. foreign calls where another thread may trigger +garbage collection" + `(multiple-value-prog1 + (progn + ,@(loop for p in objects + collect `(push-word-on-c-stack + (int-sap (sb!kernel:get-lisp-obj-address ,p)))) + ,@body) + ;; If the body returned normally, we should restore the stack pointer + ;; for the benefit of any following code in the same function. If + ;; there's a non-local exit in the body, sp is garbage anyway and + ;; will get set appropriately from {a, the} frame pointer before it's + ;; next needed + (pop-words-from-c-stack ,(length objects))))