vm: introduce sframe instruction.

This is for allocating a new frame purely on the stack.  The
frame will not be captured by lexical closures, and so can
only be used for non-shared variables and additional
compiler-generated temporaries (if registers run out, for
instance).

* share/txr/stdlib/asm.tl (op-sframe, sframe): New opcode
class and opcode.

* vm.c (vm_do_frame): New static function for the common
implementation of frame and sframe.
(vm_frame): Now just a call with vm_do_frame, passing the flag
indicating that closure capture is enabled for this
environment frame.
(vm_sframe): New static function.

* vmop.h: Regenerated.

1 files changed, 15 insertions, 2 deletions

diff --git a/vm.c b/vm.c
index 128b8f29..7759500c 100644
--- a/vm.c
+++ b/vm.c
@@ -262,7 +262,7 @@ INLINE void vm_set(struct vm_env *dspl, unsigned ref, val newval)
     mut(env->vec);
 }
 
-static void vm_frame(struct vm *vm, vm_word_t insn)
+static void vm_do_frame(struct vm *vm, vm_word_t insn, int capturable)
 {
   int lev = vm_insn_extra(insn);
   int size = vm_insn_operand(insn);
@@ -272,11 +272,21 @@ static void vm_frame(struct vm *vm, vm_word_t insn)
 
   vm->lev = lev;
   vm->dspl[lev].mem = coerce(val *, zalloca(size * sizeof (val *)));
-  vm->dspl[lev].vec = num_fast(size);
+  vm->dspl[lev].vec = (capturable ? num_fast(size) : 0);
   vm_execute(vm);
   vm->lev = lev - 1;
 }
 
+static void vm_frame(struct vm *vm, vm_word_t insn)
+{
+  vm_do_frame(vm, insn, 1);
+}
+
+static void vm_sframe(struct vm *vm, vm_word_t insn)
+{
+  vm_do_frame(vm, insn, 0);
+}
+
 static void vm_dframe(struct vm *vm, vm_word_t insn)
 {
   val saved_dyn_env = dyn_env;
@@ -610,6 +620,9 @@ static val vm_execute(struct vm *vm)
     case FRAME:
       vm_frame(vm, insn);
       break;
+    case SFRAME:
+      vm_sframe(vm, insn);
+      break;
     case DFRAME:
       vm_dframe(vm, insn);
       break;