From 22b0ce775dea2944579f33e65c7a12c48e698cb7 Mon Sep 17 00:00:00 2001
From: tali <iitalics@gmail.com>
Date: Wed, 29 Nov 2023 23:06:12 -0500
Subject: [PATCH] compile if expressions into conditional branches

---
 bin/main.ml        |  2 +-
 lib/compile/bcc.ml | 17 +++++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/bin/main.ml b/bin/main.ml
index 3c329fe..162774f 100644
--- a/bin/main.ml
+++ b/bin/main.ml
@@ -5,7 +5,7 @@ let[@warning "-26"] () =
   Logs.set_level (Some Logs.Debug);
 
   try
-    let ast = parse "val ret = 1 + 1 == 2" in
+    let ast = parse "val x = 3 val y = 5 val output = 2 * (if(9 < 8) x else 1 + y)" in
     let prog = compile ast in
     let ret = run prog in
     Fmt.pr "{\"program\":%a,\"output\":%a}" Code.pp_program prog Value.pp ret
diff --git a/lib/compile/bcc.ml b/lib/compile/bcc.ml
index 3cd03b4..ad62b11 100644
--- a/lib/compile/bcc.ml
+++ b/lib/compile/bcc.ml
@@ -50,6 +50,23 @@ let compile modl =
             emit (NOT ret)
         | _ -> Fmt.failwith "Bcc.compile_exp: TODO: %S" (Ast.string_of_binop op));
         Reg ret
+    | Ast.If (cnd, e1, e2) ->
+        let l1 = Code.make_basic_block [] in
+        let l2 = Code.make_basic_block [] in
+        let jp = Code.make_basic_block [] in
+        let tmp = !sp in
+        emit (CBR (compile_exp env cnd, l1, l2));
+        sp := tmp;
+        bb := l1;
+        emit_mov tmp (compile_exp env e1);
+        emit (JMP jp);
+        sp := tmp;
+        bb := l2;
+        emit_mov tmp (compile_exp env e2);
+        emit (JMP jp);
+        sp := tmp + 1;
+        bb := jp;
+        Reg tmp
     | Ast.Obj body -> compile_obj env body
     | _ -> failwith "Bcc.compile_exp: TODO"
   and compile_obj env items =