src/assembly/sparc/array.lisp

   1 ;;;; support routines for arrays and vectors
   2
   3 ;;;; This software is part of the SBCL system. See the README file for
   4 ;;;; more information.
   5 ;;;;
   6 ;;;; This software is derived from the CMU CL system, which was
   7 ;;;; written at Carnegie Mellon University and released into the
   8 ;;;; public domain. The software is in the public domain and is
   9 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
  10 ;;;; files for more information.
  11
  12 (in-package "SB!VM")
  13
  14 (define-assembly-routine (allocate-vector
  15                           (:policy :fast-safe)
  16                           (:translate allocate-vector)
  17                           (:arg-types positive-fixnum
  18                                       positive-fixnum
  19                                       positive-fixnum))
  20                          ((:arg type any-reg a0-offset)
  21                           (:arg length any-reg a1-offset)
  22                           (:arg words any-reg a2-offset)
  23                           (:res result descriptor-reg a0-offset)
  24
  25                           (:temp ndescr non-descriptor-reg nl0-offset)
  26                           (:temp gc-temp non-descriptor-reg nl1-offset)
  27                           (:temp vector descriptor-reg a3-offset))
  28   (pseudo-atomic ()
  29     ;; boxed words == unboxed bytes
  30     (inst add ndescr words (* (1+ vector-data-offset) n-word-bytes))
  31     (inst andn ndescr 7)
  32     (allocation vector ndescr other-pointer-lowtag :temp-tn gc-temp)
  33     (inst srl ndescr type word-shift)
  34     (storew ndescr vector 0 other-pointer-lowtag)
  35     (storew length vector vector-length-slot other-pointer-lowtag))
  36   ;; This makes sure the zero byte at the end of a string is paged in so
  37   ;; the kernel doesn't bitch if we pass it the string.
  38   ;;
  39   ;; RLT comments in CMUCL about changing the following line to
  40   ;; store at -1 instead of 0:
  41   ;;   This used to write to the word after the last allocated word.  I
  42   ;;   (RLT) made it write to the last allocated word, which is where
  43   ;;   the zero-byte of the string is.  Look at the deftransform for
  44   ;;   make-array in array-tran.lisp.  For strings we always allocate
  45   ;;   enough space to hold the zero-byte.
  46   ;; Which is most certainly motivated by the fact that this store (if
  47   ;; performed on gencgc) overwrites the first word of the following
  48   ;; page -- destroying the first object of an unrelated allocation region!
  49   ;;
  50   ;; But the CMUCL fix breaks :ELEMENT-TYPE NIL strings, so we'd need a
  51   ;; branch to figure out whether to do it.  Until and unless someone
  52   ;; demonstrates that gencgc actually gives us uncommitted memory, I'm
  53   ;; just not doing it at all:  -- DFL
  54   #!-gencgc
  55   (storew zero-tn alloc-tn 0)
  56   (move result vector))