Fix signed remainder assumption

codegen-luajit/runtime/runtime.lua

@@ -24,6 +24,7 @@ do
 	local sub = {}
 	local mul = {}
 	local div = {}
+	local rem = {}
 	local neg = {}
 	local copysign = {}
 	local nearest = {}
@@ -78,6 +79,21 @@ do
 		return (i64(u64(lhs) / u64(rhs)))
 	end
 
+	function rem.u32(lhs, rhs)
+		assert(rhs ~= 0, "division by zero")
+
+		lhs = to_number(u32(lhs))
+		rhs = to_number(u32(rhs))
+
+		return (to_signed(lhs % rhs))
+	end
+
+	function rem.u64(lhs, rhs)
+		assert(rhs ~= 0, "division by zero")
+
+		return (i64(u64(lhs) % u64(rhs)))
+	end
+
 	function neg.num(num)
 		return -num
 	end
@@ -106,6 +122,7 @@ do
 	module.sub = sub
 	module.mul = mul
 	module.div = div
+	module.rem = rem
 	module.neg = neg
 	module.copysign = copysign
 	module.nearest = nearest

codegen-luajit/src/analyzer/operator.rs

@@ -6,9 +6,7 @@ pub fn bin_symbol_of(op: BinOpType) -> Option<&'static str> {
 		BinOpType::Sub_I64 | BinOpType::Sub_FN => "-",
 		BinOpType::Mul_I64 | BinOpType::Mul_FN => "*",
 		BinOpType::DivS_I64 | BinOpType::Div_FN => "/",
-		BinOpType::RemS_I32 | BinOpType::RemU_I32 | BinOpType::RemS_I64 | BinOpType::RemU_I64 => {
+		BinOpType::RemS_I64 => "%",
-			"%"
-		}
 		_ => return None,
 	};
 

codegen-luajit/src/translator.rs

@@ -238,7 +238,9 @@ fn write_local_operation(head: &str, tail: &str, w: &mut dyn Write) -> Result<()
 		("abs" | "ceil" | "floor" | "sqrt" | "min" | "max", _) => {
 			write!(w, "local {head}_{tail} = math.{head} ")
 		}
-
+		("rem", "i32") => {
+			write!(w, "local {head}_{tail} = math.fmod ")
+		}
 		_ => write!(w, "local {head}_{tail} = rt.{head}.{tail} "),
 	}
 }