From b2455dc91ce7d43ea883ea5d2ec8adb6e90fc4d4 Mon Sep 17 00:00:00 2001
From: Rune Tynan <runetynan@gmail.com>
Date: Mon, 13 Feb 2023 23:16:56 -0500
Subject: [PATCH] Add mentioned from_raw_bytes constructor

---
 .../src/mir/interpret/allocation.rs             | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/compiler/rustc_middle/src/mir/interpret/allocation.rs b/compiler/rustc_middle/src/mir/interpret/allocation.rs
index 2ddfdbbc25a..974db3f4402 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation.rs
@@ -270,6 +270,23 @@ pub fn subrange(self, subrange: AllocRange) -> AllocRange {
 
 // The constructors are all without extra; the extra gets added by a machine hook later.
 impl<Prov: Provenance, Bytes: AllocBytes> Allocation<Prov, (), Bytes> {
+    /// Creates an allocation from an existing `Bytes` value - this is needed for miri FFI support
+    pub fn from_raw_bytes<'a>(
+        bytes: Bytes,
+        align: Align,
+        mutability: Mutability,
+    ) -> Self {
+        let size = Size::from_bytes(bytes.len());
+        Self {
+            bytes,
+            provenance: ProvenanceMap::new(),
+            init_mask: InitMask::new(size, true),
+            align,
+            mutability,
+            extra: (),
+        }
+    }
+
     /// Creates an allocation initialized by the given bytes
     pub fn from_bytes<'a>(
         slice: impl Into<Cow<'a, [u8]>>,