From 762f52b714871b475db7aceb4fc6784333df5e82 Mon Sep 17 00:00:00 2001
From: Richard Feldman <oss@rtfeldman.com>
Date: Fri, 16 Feb 2024 20:32:13 -0500
Subject: [PATCH] Use ListLenU64 where it's needed over ListLenUsize

---
 crates/compiler/mono/src/ir/pattern.rs | 27 ++++++++++++--------------
 1 file changed, 12 insertions(+), 15 deletions(-)

diff --git a/crates/compiler/mono/src/ir/pattern.rs b/crates/compiler/mono/src/ir/pattern.rs
index 155b3a2641..e04d6f72f4 100644
--- a/crates/compiler/mono/src/ir/pattern.rs
+++ b/crates/compiler/mono/src/ir/pattern.rs
@@ -1397,22 +1397,20 @@ pub(crate) fn build_list_index_probe<'a>(
     list_sym: Symbol,
     list_index: &ListIndex,
 ) -> (Symbol, impl DoubleEndedIterator<Item = Store<'a>>) {
-    let usize_layout = Layout::usize(env.target_info);
-
     let list_index = list_index.0;
     let index_sym = env.unique_symbol();
 
     let (opt_len_store, opt_offset_store, index_store) = if list_index >= 0 {
         let index_expr = Expr::Literal(Literal::Int((list_index as i128).to_ne_bytes()));
 
-        let index_store = (index_sym, usize_layout, index_expr);
+        let index_store = (index_sym, Layout::U64, index_expr);
 
         (None, None, index_store)
     } else {
         let len_sym = env.unique_symbol();
         let len_expr = Expr::Call(Call {
             call_type: CallType::LowLevel {
-                op: LowLevel::ListLenUsize,
+                op: LowLevel::ListLenU64,
                 update_mode: env.next_update_mode_id(),
             },
             arguments: env.arena.alloc([list_sym]),
@@ -1430,9 +1428,9 @@ pub(crate) fn build_list_index_probe<'a>(
             arguments: env.arena.alloc([len_sym, offset_sym]),
         });
 
-        let len_store = (len_sym, usize_layout, len_expr);
-        let offset_store = (offset_sym, usize_layout, offset_expr);
-        let index_store = (index_sym, usize_layout, index_expr);
+        let len_store = (len_sym, Layout::U64, len_expr);
+        let offset_store = (offset_sym, Layout::U64, offset_expr);
+        let index_store = (index_sym, Layout::U64, index_expr);
 
         (Some(len_store), Some(offset_store), index_store)
     };
@@ -1560,17 +1558,16 @@ fn store_list_rest<'a>(
     if let Some((index, Some(rest_sym))) = opt_rest {
         is_productive = true;
 
-        let usize_layout = Layout::usize(env.target_info);
-
         let total_dropped = list_arity.min_len();
-
         let total_dropped_sym = env.unique_symbol();
         let total_dropped_expr = Expr::Literal(Literal::Int((total_dropped as u128).to_ne_bytes()));
 
         let list_len_sym = env.unique_symbol();
         let list_len_expr = Expr::Call(Call {
             call_type: CallType::LowLevel {
-                op: LowLevel::ListLenUsize,
+                // Must use ListLenU64 here because we're using it with List.sublist,
+                // which takes U64s for start and len.
+                op: LowLevel::ListLenU64,
                 update_mode: env.next_update_mode_id(),
             },
             arguments: env.arena.alloc([list_sym]),
@@ -1596,10 +1593,10 @@ fn store_list_rest<'a>(
             arguments: env.arena.alloc([list_sym, start_sym, rest_len_sym]),
         });
         let needed_stores = [
-            (total_dropped_sym, total_dropped_expr, usize_layout),
-            (list_len_sym, list_len_expr, usize_layout),
-            (rest_len_sym, rest_len_expr, usize_layout),
-            (start_sym, start_expr, usize_layout),
+            (total_dropped_sym, total_dropped_expr, Layout::U64),
+            (list_len_sym, list_len_expr, Layout::U64),
+            (rest_len_sym, rest_len_expr, Layout::U64),
+            (start_sym, start_expr, Layout::U64),
             (*rest_sym, rest_expr, list_layout),
         ];
         for (sym, expr, lay) in needed_stores.into_iter().rev() {