New: virtual machine with assembler.

This commit is the start of compiler work to make TXR Lisp
execute faster. In six days of part time work, we now have a
register-style virtual machine with 32 instructions, handling
exceptions, unwind-protect, lexical closures, and global
environment access/mutation. We have a complete assembler and
disassembler for this machine. The assembler supports labels
with forward referencing with backpatching, and features
pseudo-ops: for instance the (mov ...) pseudo-instruction
chooses one of three kinds of specific move instruction based
on the operands.

* Makelfile (OBJS): Add vm.o.

* eval.c (lookup_sym_lisp1): Static function becomes external;
the virtual machine needs to use this to support that style
of lookup.

* genvmop.txr: New file. This is the generator for the
"vmop.h" header.

* lib.c (func_vm): New function.
(generic_funcall): Handle the FVM function type via new
vm_execute_closure function. In the variadic case, we want
to avoid the argument copying which we do for the sake of C
functions that get their fixed arguments directly, and then
just the trailing arguments. Thus the code is restructured a
bit in order to switch twice on the function type.
(init): Call vm_init.

* lib.h (functype_t): New enum member FVM.
(struct func): New member in the .f union: vm_desc.
(func_vm): Declared.

* lisplib.c (set_dlt_entries_impl): New static function,
formed from set_dlt_entries.
(set_dlt_entries): Reduced to wrapper for
set_dlt_entries_impl, passing in the user package.
(set_dlt_entries_sys): New static function: like
set_dlt_entries but targetting the sys package.
(asm_instantiate, asm_set_entries): New static functions.
(lisplib_init): Auto-load the sys:assembler class.

* share/txr/stdlib/asm.tl: New file.

* vm.c, vm.h, vmop.h: New files.

1 files changed, 18 insertions, 0 deletions

diff --git a/genvmop.txr b/genvmop.txr
new file mode 100644
index 00000000..31c6062a
--- /dev/null
+++ b/genvmop.txr
@@ -0,0 +1,18 @@
+@(include "asm")
+@(in-package :sys)
+@(bind oc @(keep-if .code %oc-list%))
+@(next "vm.h")
+@(collect)
+@{copyright}
+@(until)
+
+@(end)
+@(output "vmop.h")
+@{copyright "\n"}
+
+typedef enum vm_op {
+@  (repeat :vars (oc))
+  @{oc.symbol :filter :upcase} = @{oc.code},
+@  (end)
+} vm_op_t;
+@(end)