;;;; CL:*FEATURES* in the target SBCL, plus some comments about other
;;;; CL:*FEATURES* tags which have special meaning to SBCL or which
;;;; have a special conventional meaning
+;;;;
+;;;; Note that the preferred way to customize the features of a local
+;;;; build of SBCL is not to edit this file, but to tweak
+;;;; customize-target-features.lisp.
;;;; This software is part of the SBCL system. See the README file for
;;;; more information.
;; you are a developer.
:sb-test
+ ;; :SB-PROPAGATE-FLOAT-TYPE and :SB-PROPAGATE-FUN-TYPE enable
+ ;; some numeric optimizer code in the target compiler. They
+ ;; correspond to the :PROPAGATE-FLOAT-TYPE and :PROPAGATE-FUN-TYPE
+ ;; features in the original CMU CL code, and while documentation
+ ;; existed for those, it seemed a little inconsistent. Despite the
+ ;; name, :SB-PROPAGATE-FLOAT-TYPE seems to control not only
+ ;; floating point optimizations, but some integer optimizations as
+ ;; well.
+ ;;
+ ;; CROSS-FLOAT-INFINITY-KLUDGE:
+ ;; * Even when these target features are enabled, the optimizations
+ ;; aren't enabled in the cross-compiler, because some of them
+ ;; depend on floating point infinities, which aren't in general
+ ;; supported on the cross-compilation host.
+ ;; * This is supported by hacking the features out of the
+ ;; *SHEBANG-FEATURES* list while we're building the cross-compiler.
+ ;; This is ugly and confusing and weird, but all the alternatives
+ ;; that I could think of seem messy and error-prone. That doesn't
+ ;; mean there's not a better way, though. Suggestions are welcome;
+ ;; or if you'd like to submit patches to make this code work
+ ;; without requiring floating point infinities, so that the entire
+ ;; problem goes away, that might be even better! -- WHN 2001-03-22
+ :sb-propagate-float-type
+ :sb-propagate-fun-type
+
;; Setting this makes more debugging information available.
;; If you aren't hacking or troubleshooting SBCL itself, you
;; probably don't want this set.
; :mp
; :mp-i486
- ;; KLUDGE: used to suppress stale code related to floating point infinities.
- ;; I intend to delete this code completely some day, since it was a pain
- ;; for me to try to work with and since all benefits it provides are
- ;; non-portable. Until I actually pull the trigger, though, I've left
- ;; various stale code in place protected with #!-SB-INFINITIES.
- ; :sb-infinities
-
;; This affects the definition of a lot of things in bignum.lisp. It
- ;; doesn't seem to be documented anywhere what systems it might apply to.
- ;; It doesn't seem to be needed for X86 systems anyway.
+ ;; doesn't seem to be documented anywhere what systems it might apply
+ ;; to. It doesn't seem to be needed for X86 systems anyway.
; :32x16-divide
- ;; This is probably true for some processor types, but not X86. It affects
- ;; a lot of floating point code.
+ ;; This is probably true for some processor types, but not X86. It
+ ;; affects a lot of floating point code.
; :negative-zero-is-not-zero
- ;; This is mentioned in cmu-user.tex, which says that it enables
- ;; the compiler to reason about integer arithmetic. It also seems to
- ;; control other fancy numeric reasoning, e.g. knowing the result type of
- ;; a remainder calculation given the type of its inputs.
- ;;
- ;; KLUDGE: Even when this is implemented for the target feature list,
- ;; the code to implement this feature will not generated in the
- ;; cross-compiler (i.e. will only be generated in the target compiler).
- ;; The reason for this is that the interval arithmetic routines used
- ;; to implement this feature are written under the assumption that
- ;; Lisp arithmetic supports plus and minus infinity, which isn't guaranteed by
- ;; ANSI Common Lisp. I've tried to mark the conditionals which implement
- ;; this kludge with the string CROSS-FLOAT-INFINITY-KLUDGE so that
- ;; sometime it might be possible to undo them (perhaps by using
- ;; nice portable :PLUS-INFINITY and :MINUS-INFINITY values instead of
- ;; implementation dependent floating infinity values, which would
- ;; admittedly involve extra consing; or perhaps by finding some cleaner
- ;; way of suppressing the construction of this code in the cross-compiler).
- ;;
- ;; KLUDGE: Even after doing the KLUDGE above, the cross-compiler doesn't work,
- ;; because some interval operations are conditional on PROPAGATE-FUN-TYPE
- ;; instead of PROPAGATE-FLOAT-TYPE. So for now, I've completely turned off
- ;; both PROPAGATE-FUN-TYPE and PROPAGATE-FLOAT-TYPE. (After I build
- ;; a compiler which works, then I can think about getting the optimization
- ;; to work.) -- WHN 19990702
- ; :propagate-float-type
-
- ;; According to cmu-user.tex, this enables the compiler to infer result
- ;; types for mathematical functions like SQRT, EXPT, and LOG, allowing
- ;; it to e.g. eliminate the possibility that a complex result will be
- ;; generated.
- ;;
- ;; KLUDGE: turned off as per the comments for PROPAGATE-FLOAT-TYPE above
- ; :propagate-fun-type
-
- ;; It's unclear to me what this does (but it was enabled in the code that I
- ;; picked up from Peter Van Eynde). -- WHN 19990224
- :constrain-float-type
+ ;; It's unclear to me what this does (but it was enabled in the code
+ ;; that I picked up from Peter Van Eynde, called CONSTRAIN-FLOAT-TYPE
+ ;; instead of SB-CONSTRAIN-FLOAT-TYPE). -- WHN 19990224
+ :sb-constrain-float-type
;; This is set in classic CMU CL, and presumably there it means
;; that the floating point arithmetic implementation
projects / sbcl.git / blobdiff