From b6fa4bc82398b09307f2e6b75e27422d1d1ecb33 Mon Sep 17 00:00:00 2001
From: Mel <einebeere@gmail.com>
Date: Tue, 19 Jul 2022 02:27:19 +0200
Subject: Implement stack hygiene

---
 pkg/lang/vm/exec.go            | 10 ++++++++++
 pkg/lang/vm/text/decompiler.go |  2 +-
 pkg/lang/vm/vm.go              |  5 ++++-
 pkg/lang/vm/vm_test.go         |  5 ++---
 4 files changed, 17 insertions(+), 5 deletions(-)

(limited to 'pkg/lang/vm')

diff --git a/pkg/lang/vm/exec.go b/pkg/lang/vm/exec.go
index f92e486..3a1ce36 100644
--- a/pkg/lang/vm/exec.go
+++ b/pkg/lang/vm/exec.go
@@ -97,6 +97,16 @@ func (vm *VM) execPushType(name string) error {
 	return nil
 }
 
+func (vm *VM) execDrop(dropAmount uint) error {
+	for i := 0; i < int(dropAmount); i++ {
+		if _, err := vm.popAndDrop(); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 func (vm *VM) execGetMember(name string) error {
 	parent, err := vm.stack.Pop()
 	if err != nil {
diff --git a/pkg/lang/vm/text/decompiler.go b/pkg/lang/vm/text/decompiler.go
index b3c8bb4..2b4e704 100644
--- a/pkg/lang/vm/text/decompiler.go
+++ b/pkg/lang/vm/text/decompiler.go
@@ -55,7 +55,6 @@ func (d *Decompiler) decompileInstruction(bc code.Raw) (string, code.Raw) {
 		code.OpPushNull,
 		code.OpPushArray,
 		code.OpPushObject,
-		code.OpDrop,
 		code.OpAnchorType,
 		code.OpAdd,
 		code.OpSub,
@@ -75,6 +74,7 @@ func (d *Decompiler) decompileInstruction(bc code.Raw) (string, code.Raw) {
 
 	// Operations that take an int.
 	case code.OpPushInt,
+		code.OpDrop,
 		code.OpGetLocal,
 		code.OpSetLocal,
 		code.OpGetEnv,
diff --git a/pkg/lang/vm/vm.go b/pkg/lang/vm/vm.go
index ff9c28e..8b47915 100644
--- a/pkg/lang/vm/vm.go
+++ b/pkg/lang/vm/vm.go
@@ -116,7 +116,10 @@ func (vm *VM) step(op code.Op) (stepDecision, error) {
 		err = vm.execPushType(name)
 
 	case code.OpDrop:
-		_, err = vm.stack.Pop()
+		dropAmount, advance := vm.code.GetUint(vm.pc)
+		vm.pc += advance
+
+		err = vm.execDrop(uint(dropAmount))
 
 	case code.OpGetGlobal:
 		panic("not implemented")
diff --git a/pkg/lang/vm/vm_test.go b/pkg/lang/vm/vm_test.go
index 7fe07dd..7e749a4 100644
--- a/pkg/lang/vm/vm_test.go
+++ b/pkg/lang/vm/vm_test.go
@@ -75,7 +75,7 @@ func TestFibonacci(t *testing.T) {
 	temp_arr_push
 
 	# Drop local 1, which was the length of the array, which we no longer need
-	drop
+	drop 1
 
 	get_local 0
 	temp_arr_len
@@ -391,8 +391,7 @@ func TestPrimes(t *testing.T) {
 		add
 		set_local 0
 
-		drop
-		drop
+		drop 2
 
 		jmp @main_loop
 	@end:
-- 
cgit 1.4.1