From 7997cf95e7f8e3b1d65da0b9ebab7d2bf8f0df0a Mon Sep 17 00:00:00 2001
From: Brendan Hansknecht <brendan.hansknecht@gmail.com>
Date: Sun, 25 Aug 2024 11:48:46 -0700
Subject: [PATCH] ensure alignment is never 0. Must be at least 1.

---
 crates/compiler/gen_llvm/src/llvm/convert.rs |  3 ++-
 crates/compiler/mono/src/layout.rs           | 12 ++++++------
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/crates/compiler/gen_llvm/src/llvm/convert.rs b/crates/compiler/gen_llvm/src/llvm/convert.rs
index 90ad7a56824..73eb20f3440 100644
--- a/crates/compiler/gen_llvm/src/llvm/convert.rs
+++ b/crates/compiler/gen_llvm/src/llvm/convert.rs
@@ -404,7 +404,8 @@ impl<'ctx> RocUnion<'ctx> {
         let mut width = self.data_width;
 
         // add padding between data and the tag id
-        width = round_up_to_alignment(width, tag_id_width);
+        let tag_id_alignment = tag_id_width.max(1);
+        width = round_up_to_alignment(width, tag_id_alignment);
 
         // add tag id
         width += tag_id_width;
diff --git a/crates/compiler/mono/src/layout.rs b/crates/compiler/mono/src/layout.rs
index 258b3bed038..bc02bb97d46 100644
--- a/crates/compiler/mono/src/layout.rs
+++ b/crates/compiler/mono/src/layout.rs
@@ -1027,7 +1027,7 @@ impl<'a> UnionLayout<'a> {
         tags.iter()
             .map(|field_layouts| LayoutRepr::struct_(field_layouts).alignment_bytes(interner))
             .max()
-            .unwrap_or(0)
+            .unwrap_or(1)
     }
 
     pub fn allocation_alignment_bytes<I>(&self, interner: &I) -> u32
@@ -1196,8 +1196,8 @@ impl Discriminant {
         }
     }
 
-    pub const fn alignment_bytes(&self) -> u32 {
-        self.stack_size()
+    pub fn alignment_bytes(&self) -> u32 {
+        self.stack_size().max(1)
     }
 
     pub const fn layout(&self) -> InLayout<'static> {
@@ -2381,9 +2381,9 @@ impl<'a, 'b> Env<'a, 'b> {
     }
 }
 
-pub const fn round_up_to_alignment(width: u32, alignment: u32) -> u32 {
+pub fn round_up_to_alignment(width: u32, alignment: u32) -> u32 {
     match alignment {
-        0 => width,
+        0 => panic!("Alignment invalid: Got 0, but alignment must be at least 1"),
         1 => width,
         _ => {
             if width % alignment > 0 {
@@ -2770,7 +2770,7 @@ impl<'a> LayoutRepr<'a> {
                 .iter()
                 .map(|x| interner.get_repr(*x).alignment_bytes(interner))
                 .max()
-                .unwrap_or(0),
+                .unwrap_or(1),
 
             Union(variant) => {
                 use UnionLayout::*;