compiler/vm: implement sys:abscond-from special form.

* share/txr/stdlib/asm.tl (abscsr): New instruction.
(op-abscsr): New opcode class, derived from op-retsr.

* share/txr/stdlib/compiler.tl: Handle sys:abscond-from via
comp-return-from method.
(compiler comp-return-from): Handle sys:abscond-from by
switching to abscsr opcode instead of ret pseudo-op.

* vm.c (vm_abscsr): New static function.
(vm_execute): Dispatch ABSCSR opcode.

* vmop.h: Regenerated.

1 files changed, 12 insertions, 0 deletions

diff --git a/vm.c b/vm.c
index 3b9c64ca..f36652f0 100644
--- a/vm.c
+++ b/vm.c
@@ -660,6 +660,15 @@ static void vm_retrr(struct vm *vm, vm_word_t insn)
   vm_no_block_err(vm, tag);
 }
 
+static void vm_abscsr(struct vm *vm, vm_word_t insn)
+{
+  val res = vm_get(vm->dspl, vm_insn_operand(insn));
+  val tag = vm_get(vm->dspl, vm_insn_extra(insn));
+
+  uw_block_abscond(tag, res);
+  vm_no_block_err(vm, tag);
+}
+
 static void vm_catch(struct vm *vm, vm_word_t insn)
 {
   unsigned catch_ip = vm_insn_bigop(insn);
@@ -852,6 +861,9 @@ static val vm_execute(struct vm *vm)
     case RETRR:
       vm_retrr(vm, insn);
       break;
+    case ABSCSR:
+      vm_abscsr(vm, insn);
+      break;
     case CATCH:
       vm_catch(vm, insn);
       break;