compiler: frame-eliminating optimization.

This optimization identifies let blocks whose variables are
not captured by closures. The variables are relocated to
registers and the frame M N ... end reg wrapping is removed.

* parser.c (read_file_common): Load version 6 files.
We remain backwards-compatible.

* share/txr/stdlib/compiler.tl (var-spy, capture-var-spy): New
structure types.
(struct compiler): New slot, var-spies.
(with-var-spy): New macro.
(compiler (alloc-new-treg, unalloc-reg-count, push-var-spy,
pop-var-spy)): New methods.
(compiler (comp-atom, compt-setq, comp-list-setq,
comp-lisp1-value)): Inform the spies in the spy notification
stack about assignments and accesses.
(compiler eliminate-frame): New method.
(compiler comp-let): Use spies to determine which variables
from this frame are captured, and if none are, then use
eliminate-frame to rename all the variables to t-registers and
drop the frame setup/teardown.
(compiler comp-lambda): Set up a capture-var-spy which
intercepts accesses and assignments within a lambda, and
informs other spies about the captures.
(%tlo-ver%): Bump compiled file version to to (6 0), because
of some behavioral changes necessary in the VM. We might
revert this if the issues are solved differently.

* vm.c (vm_getz): Do not null out T registers.
(vm_execute_toplevel, vm_execute_closure): Use zalloca to
allocate the register part of the frame, so T registers are
initialized to nil.

1 files changed, 1 insertions, 1 deletions

diff --git a/parser.c b/parser.c
index d0c60578..5282b75f 100644
--- a/parser.c
+++ b/parser.c
@@ -741,7 +741,7 @@ static val read_file_common(val self, val stream, val error_stream, val compiled
 
     if (compiled && first) {
       val major = car(form);
-      if (lt(major, one) || gt(major, num_fast(5)))
+      if (lt(major, one) || gt(major, num_fast(6)))
         uw_throwf(error_s,
                   lit("cannot load ~s: version number mismatch"),
                   stream, nao);