From 8ad9960e208fbff07317d8b34883774edbe9b82b Mon Sep 17 00:00:00 2001
From: Nick Fitzgerald <fitzgen@gmail.com>
Date: Tue, 10 Feb 2026 14:08:06 -0800
Subject: [PATCH 1/2] Implement `serde` support for our OOM-handling
 `SecondaryMap`

---
 cranelift/entity/src/map.rs                   | 15 ++++++
 crates/core/src/alloc/vec.rs                  |  6 +++
 .../environ/src/collections/secondary_map.rs  | 46 ++++++++++++++++++-
 3 files changed, 66 insertions(+), 1 deletion(-)

diff --git a/cranelift/entity/src/map.rs b/cranelift/entity/src/map.rs
index 15db457ebf45..c576b4673ee3 100644
--- a/cranelift/entity/src/map.rs
+++ b/cranelift/entity/src/map.rs
@@ -212,6 +212,21 @@ where
     }
 }
 
+impl<K, V> From<Vec<V>> for SecondaryMap<K, V>
+where
+    K: EntityRef,
+    V: Clone + Default,
+{
+    fn from(elems: Vec<V>) -> Self {
+        let default = Default::default();
+        Self {
+            elems,
+            default,
+            unused: PhantomData,
+        }
+    }
+}
+
 impl<K, V> FromIterator<(K, V)> for SecondaryMap<K, V>
 where
     K: EntityRef,
diff --git a/crates/core/src/alloc/vec.rs b/crates/core/src/alloc/vec.rs
index b4a904acb3d7..dc66a921fb9e 100644
--- a/crates/core/src/alloc/vec.rs
+++ b/crates/core/src/alloc/vec.rs
@@ -264,6 +264,12 @@ impl<'a, T> IntoIterator for &'a mut Vec<T> {
     }
 }
 
+impl<T> From<Vec<T>> for StdVec<T> {
+    fn from(v: Vec<T>) -> Self {
+        v.inner
+    }
+}
+
 impl<T> From<StdVec<T>> for Vec<T> {
     fn from(inner: StdVec<T>) -> Self {
         Self { inner }
diff --git a/crates/environ/src/collections/secondary_map.rs b/crates/environ/src/collections/secondary_map.rs
index 6667010f6528..cfa1c961c234 100644
--- a/crates/environ/src/collections/secondary_map.rs
+++ b/crates/environ/src/collections/secondary_map.rs
@@ -1,6 +1,7 @@
-use crate::error::OutOfMemory;
+use crate::{collections::Vec, error::OutOfMemory};
 use core::{fmt, ops::Index};
 use cranelift_entity::{EntityRef, SecondaryMap as Inner};
+use serde::ser::SerializeSeq;
 
 /// Like [`cranelift_entity::SecondaryMap`] but all allocation is fallible.
 pub struct SecondaryMap<K, V>
@@ -142,3 +143,46 @@ where
         &self.inner[k]
     }
 }
+
+impl<K, V> From<Vec<V>> for SecondaryMap<K, V>
+where
+    K: EntityRef,
+    V: Clone + Default,
+{
+    fn from(values: Vec<V>) -> Self {
+        let values: alloc::vec::Vec<V> = values.into();
+        let inner = Inner::from(values);
+        Self { inner }
+    }
+}
+
+impl<K, V> serde::ser::Serialize for SecondaryMap<K, V>
+where
+    K: EntityRef,
+    V: Clone + serde::ser::Serialize,
+{
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        let mut seq = serializer.serialize_seq(Some(self.capacity()))?;
+        for elem in self.values() {
+            seq.serialize_element(elem)?;
+        }
+        seq.end()
+    }
+}
+
+impl<'de, K, V> serde::de::Deserialize<'de> for SecondaryMap<K, V>
+where
+    K: EntityRef,
+    V: Clone + Default + serde::de::Deserialize<'de>,
+{
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        let values: Vec<V> = serde::de::Deserialize::deserialize(deserializer)?;
+        Ok(Self::from(values))
+    }
+}

From 87ae93c189728113bfe0c5a725fe043b6fd060ba Mon Sep 17 00:00:00 2001
From: Nick Fitzgerald <fitzgen@gmail.com>
Date: Wed, 11 Feb 2026 11:21:09 -0800
Subject: [PATCH 2/2] remove duplicate impl from bad rebase

---
 crates/core/src/alloc/vec.rs | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/crates/core/src/alloc/vec.rs b/crates/core/src/alloc/vec.rs
index dc66a921fb9e..27128c9f9455 100644
--- a/crates/core/src/alloc/vec.rs
+++ b/crates/core/src/alloc/vec.rs
@@ -276,12 +276,6 @@ impl<T> From<StdVec<T>> for Vec<T> {
     }
 }
 
-impl<T> From<Vec<T>> for StdVec<T> {
-    fn from(v: Vec<T>) -> Self {
-        v.inner
-    }
-}
-
 impl<T> From<Box<[T]>> for Vec<T> {
     fn from(boxed_slice: Box<[T]>) -> Self {
         Self::from(StdVec::from(boxed_slice))