Research V6 development

Work on file usr/source/s4/alloc.s

Co-Authored-By: Dennis Ritchie <dmr@research.uucp>
Synthesized-from: v6

diff --git a/usr/source/s4/alloc.s b/usr/source/s4/alloc.s
new file mode 100644 (file)
index 0000000..fc5b554
--- /dev/null
+++ b/usr/source/s4/alloc.s
@@ -0,0 +1,165 @@
+/      storage allocator for use with C
+/
+/
+/
+/      hand-tooled from C compilation to modify save-return
+/      so that it can be called from within the C save
+/      when running with coroutines
+/
+/#
+//*
+/ *    C storage allocator
+/ *    (circular first fit strategy)
+/ */
+/#define BLOK 512
+/#define BUSY 01
+/
+/char *allocs[2] {             /*initial empty arena*/
+/      &allocs[1],
+/      &allocs[0]
+/};
+/struct { int word; };
+/char **allocp &allocs[1];     /*current search pointer*/
+/char **alloct &allocs[1];     /*top of arena (last cell)*/
+/
+/alloc(nbytes)
+/{
+/      register int nwords;
+/      register char **p, **q;
+/      static char **t;
+/
+/      allocs[0].word =| BUSY; /*static initialization*/
+/      allocs[1].word =| BUSY;
+/
+/      nwords = (nbytes+(2*sizeof(p)-1))/sizeof(p);
+/      for(p=allocp;;) {
+/              do {
+/                      if((p->word&BUSY)==0) {
+/                              while(((q = *p)->word&BUSY)==0)
+/                                      *p = *q;
+/                              if(q >= &p[nwords])
+/                                      goto found;
+/                      }
+/                      q = p;
+/                      p = p->word & ~BUSY;
+/              } while(q>=allocp || p<allocp);
+/              if((*alloct=t=sbrk(BLOK*sizeof(p))) == -1)
+/                      return(-1);
+/              if(t!=alloct+1)
+/                      alloct->word =| BUSY;
+/              alloct = (*t = &t[BLOK]-1);
+/              *alloct = allocs;
+/              alloct->word =| BUSY;
+/      }
+/found:
+/      allocp = &p[nwords];
+/      if(q>allocp)
+/              *allocp = *p;
+/      *p = allocp.word|BUSY;
+/      return(p+1);
+/}
+/
+/free(p)
+/char **p;
+/{
+/      allocp = p-1;
+/      allocp->word =& ~BUSY;
+/}
+.globl _allocs
+.data
+_allocs=.
+2+_allocs
+_allocs
+.globl _allocp
+.data
+_allocp=.
+2+_allocs
+.globl _alloct
+.data
+_alloct=.
+2+_allocs
+.globl _alloc
+
+.globl _sbrk
+.text
+_alloc:
+mov    r5,-(sp)
+mov    sp,r5
+mov    r4,-(sp)
+mov    r3,-(sp)
+mov    r2,-(sp)
+bis    $1,_allocs
+bis    $1,2+_allocs
+mov    4(r5),r4
+add    $3,r4
+asr    r4
+mov    _allocp,r3
+jbr    L6
+L7:mov r3,r2
+mov    (r3),r3
+bic    $!177776,r3
+cmp    r2,_allocp
+jhis   L6
+cmp    r3,_allocp
+jlo    L6
+mov    $2000,-(sp)
+jsr    pc,*$_sbrk
+tst    (sp)+
+mov    r0,t
+mov    r0,*_alloct
+cmp    $177777,r0
+jeq    L11
+mov    _alloct,r0
+add    $2,r0
+cmp    t,r0
+jeq    L12
+bis    $1,*_alloct
+L12:mov        t,r0
+add    $1776,r0
+mov    r0,*t
+mov    r0,_alloct
+mov    $_allocs,*_alloct
+bis    $1,*_alloct
+L6:bit $1,(r3)
+jeq    L8
+jbr    L7
+L20001:mov     (r2),(r3)
+L8:mov (r3),r2
+bit    $1,(r2)
+jeq    L20001
+mov    r4,r0
+asl    r0
+add    r3,r0
+cmp    r2,r0
+jlo    L7
+mov    r4,r0
+asl    r0
+add    r3,r0
+mov    r0,_allocp
+cmp    r2,r0
+jlos   L13
+mov    (r3),*_allocp
+L13:mov        _allocp,r0
+bis    $1,r0
+mov    r0,(r3)
+mov    r3,r0
+add    $2,r0
+L11:
+mov    (sp)+,r2
+mov    (sp)+,r3
+mov    (sp)+,r4
+mov    (sp)+,r5
+rts    pc
+.globl _free
+.text
+_free:
+mov    r5,-(sp)
+mov    sp,r5
+mov    4(r5),r0
+add    $177776,r0
+mov    r0,_allocp
+bic    $!177776,*_allocp
+mov    (sp)+,r5
+rts    pc
+.bss
+t:     .=.+2