compiler: use counter instead of preallocating tregs.

* share/txr/stdlib/compiler.tl (compiler): new slot,
treg-cntr; slot nregs removed; tregs stack initialized to
empty list.
(compiler alloc-treg): Take from stack if possible,
otherwise create new treg using counter, up to 255.
(usr:compile-toplevel): Referenceco.treg-cntr for register
count, rather than removed co.nreg.

1 files changed, 7 insertions, 7 deletions

diff --git a/share/txr/stdlib/compiler.tl b/share/txr/stdlib/compiler.tl
index 8f64adca..fe75cd62 100644
--- a/share/txr/stdlib/compiler.tl
+++ b/share/txr/stdlib/compiler.tl
@@ -106,11 +106,12 @@
         (< me.lev lev)))))
 
 (defstruct compiler nil
+  (treg-cntr 1)
   (dreg-cntr 0)
   (fidx-cntr 0)
   (nlev 2)
   (nreg 1)
-  (tregs (mapcar (op list t) (range 1 255)))
+  (tregs nil)
   (dreg (hash :eql-based))
   (data (hash :eql-based))
   (fidx (hash :eql-based))
@@ -140,11 +141,10 @@
   (vec-list [mapcar me.ftab (range* 0 me.fidx-cntr)]))
 
 (defmeth compiler alloc-treg (me)
-  (let ((treg (pop me.tregs)))
-    (unless treg
-      (compile-error me.last-form "code too complex: out of registers"))
-    (set me.nreg (max me.nreg (succ (cadr treg))))
-    treg))
+  (cond
+    (me.tregs (pop me.tregs))
+    ((< me.treg-cntr 256) ^(t ,(pinc me.treg-cntr)))
+    (t (compile-error me.last-form "code too complex: out of registers"))))
 
 (defmeth compiler free-treg (me treg)
   (when (and (eq t (car treg)) (neq 0 (cadr treg)))
@@ -1251,4 +1251,4 @@
                                         (release-deferred-warnings))))
            (frag co.(compile oreg (new env co co) xexp)))
       as.(asm ^(,*frag.code (end ,frag.oreg)))
-      (vm-make-desc co.nlev co.nreg as.buf co.(get-datavec) co.(get-funvec)))))
+      (vm-make-desc co.nlev co.treg-cntr as.buf co.(get-datavec) co.(get-funvec)))))