feat: Allow signed narrow-width loads (#62)

js/expression.ml

@@ -83,11 +83,12 @@ let global_set wasm_mod name value =
   let scope = get wasm_mod "global" in
   meth_call scope "set" [| inject (string name); inject value |]
 
-let load wasm_mod byts offset align typ ptr =
+let load wasm_mod byts ?(signed=false) offset align typ ptr =
   meth_call global##.binaryen "_BinaryenLoad"
     [|
       inject wasm_mod;
       inject byts;
+      inject signed;
       inject offset;
       inject align;
       inject typ;

src/binaryen_stubs_expressions.c

@@ -204,21 +204,22 @@ caml_binaryen_global_set(value _module, value _name, value _val) {
 }
 
 CAMLprim value
-caml_binaryen_load(value _module, value _bytes, value _offset, value _align, value _ty, value _ptr) {
-  CAMLparam5(_module, _bytes, _offset, _align, _ty);
-  CAMLxparam1(_ptr);
+caml_binaryen_load(value _module, value _bytes, value _signed_, value _offset, value _align, value _ty, value _ptr) {
+  CAMLparam5(_module, _bytes, _signed_, _offset, _align);
+  CAMLxparam2(_ty, _ptr);
   BinaryenModuleRef module = BinaryenModuleRef_val(_module);
   int bytes = Int_val(_bytes);
+  int8_t signed_ = Bool_val(_signed_);
   int offset = Int_val(_offset);
   int align = Int_val(_align);
   BinaryenType ty = BinaryenType_val(_ty);
   BinaryenExpressionRef ptr = BinaryenExpressionRef_val(_ptr);
-  BinaryenExpressionRef exp = BinaryenLoad(module, bytes, 0, offset, align, ty, ptr);
+  BinaryenExpressionRef exp = BinaryenLoad(module, bytes, signed_, offset, align, ty, ptr);
   CAMLreturn(alloc_BinaryenExpressionRef(exp));
 }
 CAMLprim value
 caml_binaryen_load__bytecode(value * argv) {
-  return caml_binaryen_load(argv[0], argv[1], argv[2], argv[3], argv[4], argv[5]);
+  return caml_binaryen_load(argv[0], argv[1], argv[2], argv[3], argv[4], argv[5], argv[6]);
 }
 
 CAMLprim value

src/expression.ml

@@ -51,9 +51,11 @@ external global_get : Module.t -> string -> Type.t -> t
 external global_set : Module.t -> string -> t -> t = "caml_binaryen_global_set"
 (** Module, name, value. *)
 
-external load : Module.t -> int -> int -> int -> Type.t -> t -> t
+external load : Module.t -> int -> bool -> int -> int -> Type.t -> t -> t
   = "caml_binaryen_load__bytecode" "caml_binaryen_load"
-(** Module, num_bytes, offset, align, type, ptr. *)
+let load wasm_mod bytes ?(signed=false) offset align ty ptr =
+  load wasm_mod bytes signed offset align ty ptr
+(** Module, num_bytes, ?signed, offset, align, type, ptr. *)
 
 external store : Module.t -> int -> int -> int -> t -> t -> Type.t -> t
   = "caml_binaryen_store__bytecode" "caml_binaryen_store"

test/test.expected

@@ -1,11 +1,15 @@
 (module
  (type $i32_i32_=>_i32 (func (param i32 i32) (result i32)))
+ (memory $0 1)
+ (export "memory" (memory $0))
  (func $adder (param $0 i32) (param $1 i32) (result i32)
   (block $add (result i32)
    (i32.add
     (select
      (local.get $0)
-     (local.get $1)
+     (i32.load8_s
+      (local.get $1)
+     )
      (i32.const 1)
     )
     (local.get $1)
@@ -15,11 +19,15 @@
 )
 (module
  (type $i32_i32_=>_i32 (func (param i32 i32) (result i32)))
+ (memory $0 1)
+ (export "memory" (memory $0))
  (func $0 (param $0 i32) (param $1 i32) (result i32)
   (i32.add
    (select
     (local.get $0)
-    (local.get $1)
+    (i32.load8_s
+     (local.get $1)
+    )
     (i32.const 1)
    )
    (local.get $1)

test/test.ml

@@ -7,18 +7,21 @@ let params = Type.create [| Type.int32; Type.int32 |]
 
 let results = Type.int32
 
-(* Get arguments 0 and 1, add them *)
-let x = Expression.local_get wasm_mod 0 Type.int32
+let x () = Expression.local_get wasm_mod 0 Type.int32
 
-let y = Expression.local_get wasm_mod 1 Type.int32
+let y () = Expression.local_get wasm_mod 1 Type.int32
 
-let select = Expression.select wasm_mod (Expression.const wasm_mod (Literal.int32 1l)) x y
+let load = Expression.load wasm_mod 1 ~signed:true 0 0 Type.int32 (y ())
 
-let add = Expression.block wasm_mod ~return_type:Type.int32 "add" [Expression.binary wasm_mod Op.add_int32 select y]
+let select = Expression.select wasm_mod (Expression.const wasm_mod (Literal.int32 1l)) (x ()) load
+
+let add = Expression.block wasm_mod ~return_type:Type.int32 "add" [Expression.binary wasm_mod Op.add_int32 select (y ())]
 
 (* Create the add function *)
 let adder = Function.add_function wasm_mod "adder" params results [||] add
 
+let _ = Memory.set_memory wasm_mod 1 Memory.unlimited "memory" [] false
+
 let _ = Module.print wasm_mod
 
 let byts, _ = Module.write wasm_mod None

virtual/expression.mli

@@ -28,7 +28,7 @@ val global_get : Module.t -> string -> Type.t -> t
 
 val global_set : Module.t -> string -> t -> t
 
-val load : Module.t -> int -> int -> int -> Type.t -> t -> t
+val load : Module.t -> int -> ?signed:bool -> int -> int -> Type.t -> t -> t
 
 val store : Module.t -> int -> int -> int -> t -> t -> Type.t -> t