diff --git a/src/ir.c b/src/ir.c
index 0d5e7d0..387ebb2 100644
--- a/src/ir.c
+++ b/src/ir.c
@@ -103,16 +103,17 @@ var push_var(reg reg) {
 }
 
 void load_args(struct label* label, var* args) {
-    struct stack_frame* dest_frame = &stack_frames[label->frame];
+    struct stack_frame* dest_frame = &stack_frames[label->frame - 1];
     uint32_t depth_diff = stack_depth - dest_frame->depth;
     if (depth_diff > 0) {
         // FIXME: should be immX!!!
-        x86_inst_add_r64_imm8(SP, depth_diff);
+        x86_inst_add_r64_imm8(SP, depth_diff * 8);
     }
     for (uint32_t arg = 0; arg < label->argc; arg++) {
         load_var(AX, args[arg]);
         x86_inst_push_r64(AX);
     }
+    stack_depth = dest_frame->depth + label->argc;
 }
 
 void jump(label l, var* args) {
@@ -126,20 +127,15 @@ void jump_table(size_t branches, label* labels, var index, var* args) {
     assert(0); // UNIMPLEMENTED
 }
 
-void jump_if(label l, var cond, var* args) {
-    struct label* label = &labels[l];
-    printf("JUMP_IF %i (%i)\n", l, label->argc);
+void jump_if(label t, label e, var cond, var* args) {
+    struct label* then = &labels[t];
+    struct label* else_ = &labels[e];
+    printf("JUMP_IF %i ELSE %i (%i)\n", t, e, then->argc);
+    assert(then->argc == else_->argc && then->frame == else_->frame);
     load_var(BX, cond);
-    load_args(label, args);
-    inst_jump_if_not_zero(label->symbol, BX);
-}
-
-void jump_unless(label l, var cond, var* args) {
-    struct label* label = &labels[l];
-    printf("JUMP_UNLESS %i (%i)\n", l, label->argc);
-    load_var(BX, cond);
-    load_args(label, args);
-    inst_jump_if_zero(label->symbol, BX);
+    load_args(then, args);
+    inst_jump_if_not_zero(then->symbol, BX);
+    inst_jump(else_->symbol);
 }
 
 var lit(uint64_t lit) {
diff --git a/src/ir.h b/src/ir.h
index 408cd27..94d53a5 100644
--- a/src/ir.h
+++ b/src/ir.h
@@ -7,6 +7,40 @@
 typedef uint32_t var;
 typedef uint32_t label;
 
+struct jump_target {
+    label label;
+    var* args;
+};
+
+/// Declare a new label in the current scope with the provided number
+/// of arguments.
+///
+/// Local variables (not part of a stack frame generated by `define` or `enter`)
+/// will not be in scope of the definition of the label.
+label declare(uint32_t argc);
+
+/// Define a label and create a new scope for local variables.
+///
+/// The new scope will have access to all of the variables
+/// of the parent scope of the label and the label's arguments,
+/// but not any local variables from previous definitions.
+void define(label label, var* args);
+
+/// Create a new scope which encompasses all local variables defined up to this point.
+///
+/// This allows nested definitions to have access to local variables.
+void enter(void);
+
+/// Jump to label, unconditionally. Ends the continuation.
+void jump(struct jump_target dest);
+
+/// Jump to `then` if `cond` is not zero; jump to `else` otherwise.
+/// Ends the continuation.
+void jump_if(struct jump_target then, struct jump_target else_, var cond);
+
+/// Jump to the `index`th destination. Ends the continuation.
+void jump_table(uint32_t destc, struct jump_target* destinations, var index);
+
 /// Call this at the beginning of execution.
 /// It performs initialization and stuff.
 void init_ir(var* argc, var* argv, var* env);
@@ -61,11 +95,8 @@ void jump(label label, var* args);
 /// `index` must not be out of bounds.
 void jump_table(size_t branches, label* labels, var index, var* args);
 
-/// Jump to label if `cond` is not zero.
-void jump_if(label label, var cond, var* args);
-
-/// Jump to label if `cond` is zero.
-void jump_unless(label label, var cond, var* args);
+/// Jump to `then` if cond is not zero, `else` if cond is zero.
+void jump_if(label then, label else_, var cond, var* args);
 
 /// Integer literal.
 var lit(uint64_t lit);
diff --git a/src/lang.c b/src/lang.c
index bd15142..bcc2583 100644
--- a/src/lang.c
+++ b/src/lang.c
@@ -473,8 +473,7 @@ void exit_expr(void) {
         case IF_CRUMB: {
             struct if_crumb* ifc = &ctx->data.if_;
             assert(ifc->state == IF_COND);
-            jump_unless(ifc->else_, ret, NULL);
-            //jump(ifc->then_, NULL);
+            jump_if(ifc->then, ifc->else_, ret, NULL);
             ifc->state = IF_THEN;
             break;
         }