expose decref_pointer_check_NULL

compiler/builtins/bitcode/src/main.zig

@@ -110,6 +110,7 @@ const utils = @import("utils.zig");
 comptime {
     exportUtilsFn(utils.test_panic, "test_panic");
     exportUtilsFn(utils.decrefC, "decref");
+    exportUtilsFn(utils.decrefCheckNullC, "decref_check_null");
 
     @export(utils.panic, .{ .name = "roc_builtins.utils." ++ "panic", .linkage = .Weak });
 }

compiler/builtins/bitcode/src/utils.zig

@@ -117,6 +117,15 @@ pub fn decrefC(
     return @call(.{ .modifier = always_inline }, decref_ptr_to_refcount, .{ bytes, alignment });
 }
 
+pub fn decrefCheckNullC(
+    bytes_or_null: ?[*]isize,
+    alignment: u32,
+) callconv(.C) void {
+    if (bytes_or_null) |bytes| {
+        return @call(.{ .modifier = always_inline }, decref_ptr_to_refcount, .{ bytes, alignment });
+    }
+}
+
 pub fn decref(
     bytes_or_null: ?[*]u8,
     data_bytes: usize,

compiler/builtins/src/bitcode.rs

@@ -83,3 +83,4 @@ pub const DEC_DIV: &str = "roc_builtins.dec.div";
 
 pub const UTILS_TEST_PANIC: &str = "roc_builtins.utils.test_panic";
 pub const UTILS_DECREF: &str = "roc_builtins.utils.decref";
+pub const UTILS_DECREF_CHECK_NULL: &str = "roc_builtins.utils.decref_check_null";

compiler/gen_llvm/src/llvm/refcounting.rs

@@ -250,6 +250,27 @@ pub fn decref_pointer<'a, 'ctx, 'env>(
     );
 }
 
+/// Assumes a pointer to the refcount
+pub fn decref_pointer_check_null<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    pointer: PointerValue<'ctx>,
+    alignment: u32,
+) {
+    let alignment = env.context.i32_type().const_int(alignment as _, false);
+    call_void_bitcode_fn(
+        env,
+        &[
+            env.builder.build_bitcast(
+                pointer,
+                env.ptr_int().ptr_type(AddressSpace::Generic),
+                "to_isize_ptr",
+            ),
+            alignment.into(),
+        ],
+        roc_builtins::bitcode::UTILS_DECREF_CHECK_NULL,
+    );
+}
+
 fn modify_refcount_struct<'a, 'ctx, 'env>(
     env: &Env<'a, 'ctx, 'env>,
     layout_ids: &mut LayoutIds<'a>,