Change %mulint primitive behavior (#7358)

* Change `%mulint` primitive behavior

* add changelog

Author: cometkim

CHANGELOG.md

@@ -28,6 +28,7 @@
 - Replace ~date with ~day in Date.make\*. https://github.com/rescript-lang/rescript/pull/7324
 - Remove `-bs-jsx-mode`. https://github.com/rescript-lang/rescript/pull/7327
 - Drop Node.js version <20 support, as it is reaching End-of-Life. https://github.com/rescript-lang/rescript-compiler/pull/7354
+- Treat `int` multiplication as a normal int32 operation instead of using `Math.imul`. https://github.com/rescript-lang/rescript/pull/7358
 
 #### :house: Internal
 

compiler/core/js_exp_make.ml

@@ -1607,14 +1607,8 @@ let int32_mul ?comment (e1 : J.expression) (e2 : J.expression) : J.expression =
   | {expression_desc = Number (Int {i = i0}); _}, e ->
     let i = is_pos_pow i0 in
     if i >= 0 then int32_lsl e (small_int i)
-    else
-      call ?comment ~info:Js_call_info.builtin_runtime_call
-        (dot (js_global "Math") Literals.imul)
-        [e1; e2]
-  | _ ->
-    call ?comment ~info:Js_call_info.builtin_runtime_call
-      (dot (js_global "Math") Literals.imul)
-      [e1; e2]
+    else to_int32 (float_mul ?comment e1 e2)
+  | _ -> to_int32 (float_mul ?comment e1 e2)
 
 let unchecked_int32_mul ?comment e1 e2 : J.expression =
   {comment; expression_desc = Bin (Mul, e1, e2)}

compiler/ext/literals.ml

@@ -50,8 +50,6 @@ let runtime = "runtime" (* runtime directory *)
 
 let stdlib = "stdlib"
 
-let imul = "imul" (* signed int32 mul *)
-
 let setter_suffix = "#="
 
 let setter_suffix_len = String.length setter_suffix

lib/es6/Primitive_hash.js

@@ -36,7 +36,7 @@ function unsafe_pop(q) {
     RE_EXN_ID: "Assert_failure",
     _1: [
       "Primitive_hash.res",
-      70,
+      73,
       12
     ],
     Error: new Error()

lib/es6/Stdlib_Int.js

@@ -46,7 +46,7 @@ function range(start, end, optionsOpt) {
     let range$2 = options.inclusive === true ? range$1 + 1 | 0 : range$1;
     length = Math.ceil(range$2 / abs(step)) | 0;
   }
-  return Stdlib_Array.fromInitializer(length, i => start + Math.imul(i, step) | 0);
+  return Stdlib_Array.fromInitializer(length, i => start + (i * step | 0) | 0);
 }
 
 function rangeWithOptions(start, end, options) {

lib/js/Primitive_hash.js

@@ -36,7 +36,7 @@ function unsafe_pop(q) {
     RE_EXN_ID: "Assert_failure",
     _1: [
       "Primitive_hash.res",
-      70,
+      73,
       12
     ],
     Error: new Error()

lib/js/Stdlib_Int.js

@@ -46,7 +46,7 @@ function range(start, end, optionsOpt) {
     let range$2 = options.inclusive === true ? range$1 + 1 | 0 : range$1;
     length = Math.ceil(range$2 / abs(step)) | 0;
   }
-  return Stdlib_Array.fromInitializer(length, i => start + Math.imul(i, step) | 0);
+  return Stdlib_Array.fromInitializer(length, i => start + (i * step | 0) | 0);
 }
 
 function rangeWithOptions(start, end, options) {

runtime/Primitive_hash.res

@@ -29,6 +29,9 @@ module String = Primitive_string_extern
 
 @send external charCodeAt: (string, int) => int = "charCodeAt"
 
+// Multiply int32 with C-style overflow behavior
+external imul: (int, int) => int = "Math.imul"
+
 type rec cell<'a> = {
   content: 'a,
   mutable next: option<cell<'a>>,
@@ -85,19 +88,19 @@ let rotl32 = (x: int, n) => lor(lsl(x, n), lsr(x, 32 - n))
 
 let hash_mix_int = (h, d) => {
   let d = ref(d)
-  d.contents = d.contents * 0xcc9e2d51
+  d.contents = imul(d.contents, 0xcc9e2d51)
   d.contents = rotl32(d.contents, 15)
-  d.contents = d.contents * 0x1b873593
+  d.contents = imul(d.contents, 0x1b873593)
   let h = ref(lxor(h, d.contents))
   h.contents = rotl32(h.contents, 13)
   h.contents + lsl(h.contents, 2) + 0xe6546b64
 }
 
 let hash_final_mix = h => {
   let h = ref(lxor(h, lsr(h, 16)))
-  h.contents = h.contents * 0x85ebca6b
+  h.contents = imul(h.contents, 0x85ebca6b)
   h.contents = lxor(h.contents, lsr(h.contents, 13))
-  h.contents = h.contents * 0xc2b2ae35
+  h.contents = imul(h.contents, 0xc2b2ae35)
   lxor(h.contents, lsr(h.contents, 16))
 }