From bfa7d44823717c30bc21abc1ca3675d0b78c80a2 Mon Sep 17 00:00:00 2001
From: DrMeepster <19316085+DrMeepster@users.noreply.github.com>
Date: Sun, 27 Feb 2022 00:48:17 -0800
Subject: [PATCH 1/2] fix box icing when it has aggregate abi

---
 compiler/rustc_codegen_ssa/src/mir/place.rs | 13 +++++++++++-
 src/test/ui/box/issue-81270-ice.rs          | 22 +++++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)
 create mode 100644 src/test/ui/box/issue-81270-ice.rs

diff --git a/compiler/rustc_codegen_ssa/src/mir/place.rs b/compiler/rustc_codegen_ssa/src/mir/place.rs
index 6976999c0e4f7..aee385ab050e4 100644
--- a/compiler/rustc_codegen_ssa/src/mir/place.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/place.rs
@@ -453,7 +453,18 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         };
         for elem in place_ref.projection[base..].iter() {
             cg_base = match elem.clone() {
-                mir::ProjectionElem::Deref => bx.load_operand(cg_base).deref(bx.cx()),
+                mir::ProjectionElem::Deref => {
+                    // custom allocators can change box's abi, making it unable to be derefed directly
+                    if cg_base.layout.ty.is_box()
+                        && matches!(cg_base.layout.abi, Abi::Aggregate { .. })
+                    {
+                        let ptr = cg_base.project_field(bx, 0).project_field(bx, 0);
+
+                        bx.load_operand(ptr).deref(bx.cx())
+                    } else {
+                        bx.load_operand(cg_base).deref(bx.cx())
+                    }
+                }
                 mir::ProjectionElem::Field(ref field, _) => {
                     cg_base.project_field(bx, field.index())
                 }
diff --git a/src/test/ui/box/issue-81270-ice.rs b/src/test/ui/box/issue-81270-ice.rs
new file mode 100644
index 0000000000000..fb42aed7aaebf
--- /dev/null
+++ b/src/test/ui/box/issue-81270-ice.rs
@@ -0,0 +1,22 @@
+// check-pass
+#![feature(allocator_api)]
+
+use std::alloc::Allocator;
+
+struct BigAllocator([usize; 2]);
+
+unsafe impl Allocator for BigAllocator {
+    fn allocate(
+        &self,
+        _: std::alloc::Layout,
+    ) -> Result<std::ptr::NonNull<[u8]>, std::alloc::AllocError> {
+        todo!()
+    }
+    unsafe fn deallocate(&self, _: std::ptr::NonNull<u8>, _: std::alloc::Layout) {
+        todo!()
+    }
+}
+
+fn main() {
+    Box::new_in((), BigAllocator([0; 2]));
+}

From d316aba04c4644093ba07d1ec8d334b599b8eb01 Mon Sep 17 00:00:00 2001
From: DrMeepster <19316085+DrMeepster@users.noreply.github.com>
Date: Sun, 27 Feb 2022 20:25:16 -0800
Subject: [PATCH 2/2] expadn abi check + condese & fix tests

---
 compiler/rustc_codegen_ssa/src/mir/place.rs                 | 2 +-
 src/test/ui/box/issue-78459-ice.rs                          | 6 ------
 .../ui/box/{issue-81270-ice.rs => large-allocator-ice.rs}   | 3 ++-
 3 files changed, 3 insertions(+), 8 deletions(-)
 delete mode 100644 src/test/ui/box/issue-78459-ice.rs
 rename src/test/ui/box/{issue-81270-ice.rs => large-allocator-ice.rs} (88%)

diff --git a/compiler/rustc_codegen_ssa/src/mir/place.rs b/compiler/rustc_codegen_ssa/src/mir/place.rs
index aee385ab050e4..809d64479084a 100644
--- a/compiler/rustc_codegen_ssa/src/mir/place.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/place.rs
@@ -456,7 +456,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 mir::ProjectionElem::Deref => {
                     // custom allocators can change box's abi, making it unable to be derefed directly
                     if cg_base.layout.ty.is_box()
-                        && matches!(cg_base.layout.abi, Abi::Aggregate { .. })
+                        && matches!(cg_base.layout.abi, Abi::Aggregate { .. } | Abi::Uninhabited)
                     {
                         let ptr = cg_base.project_field(bx, 0).project_field(bx, 0);
 
diff --git a/src/test/ui/box/issue-78459-ice.rs b/src/test/ui/box/issue-78459-ice.rs
deleted file mode 100644
index 89f75fea15b1d..0000000000000
--- a/src/test/ui/box/issue-78459-ice.rs
+++ /dev/null
@@ -1,6 +0,0 @@
-// check-pass
-#![feature(allocator_api)]
-
-fn main() {
-    Box::new_in((), &std::alloc::Global);
-}
diff --git a/src/test/ui/box/issue-81270-ice.rs b/src/test/ui/box/large-allocator-ice.rs
similarity index 88%
rename from src/test/ui/box/issue-81270-ice.rs
rename to src/test/ui/box/large-allocator-ice.rs
index fb42aed7aaebf..3ef1171ff50d9 100644
--- a/src/test/ui/box/issue-81270-ice.rs
+++ b/src/test/ui/box/large-allocator-ice.rs
@@ -1,4 +1,4 @@
-// check-pass
+// build-pass
 #![feature(allocator_api)]
 
 use std::alloc::Allocator;
@@ -18,5 +18,6 @@ unsafe impl Allocator for BigAllocator {
 }
 
 fn main() {
+    Box::new_in((), &std::alloc::Global);
     Box::new_in((), BigAllocator([0; 2]));
 }