From c54672e25f41b8ef41d0ff94da8c9a06fd6ed0b5 Mon Sep 17 00:00:00 2001
From: Ben Kimock <kimockb@gmail.com>
Date: Thu, 15 Jun 2023 18:02:55 -0400
Subject: [PATCH] Disable alignment checks on i686-pc-windows-msvc

---
 .../src/check_alignment.rs                    |  3 +++
 tests/ui/mir/mir_alignment_check.rs           |  1 +
 ...ir_alignment_check_i686-pc-windows-msvc.rs | 21 +++++++++++++++++++
 3 files changed, 25 insertions(+)
 create mode 100644 tests/ui/mir/mir_alignment_check_i686-pc-windows-msvc.rs

diff --git a/compiler/rustc_mir_transform/src/check_alignment.rs b/compiler/rustc_mir_transform/src/check_alignment.rs
index ef64f70fdf3..3987614f951 100644
--- a/compiler/rustc_mir_transform/src/check_alignment.rs
+++ b/compiler/rustc_mir_transform/src/check_alignment.rs
@@ -15,6 +15,9 @@
 
 impl<'tcx> MirPass<'tcx> for CheckAlignment {
     fn is_enabled(&self, sess: &Session) -> bool {
+        if sess.target.llvm_target == "i686-pc-windows-msvc" {
+            return false;
+        }
         sess.opts.debug_assertions
     }
 
diff --git a/tests/ui/mir/mir_alignment_check.rs b/tests/ui/mir/mir_alignment_check.rs
index 68a5384b30d..d1bf3d46a7c 100644
--- a/tests/ui/mir/mir_alignment_check.rs
+++ b/tests/ui/mir/mir_alignment_check.rs
@@ -1,5 +1,6 @@
 // run-fail
 // ignore-wasm32-bare: No panic messages
+// ignore-i686-pc-windows-msvc: #112480
 // compile-flags: -C debug-assertions
 // error-pattern: misaligned pointer dereference: address must be a multiple of 0x4 but is
 
diff --git a/tests/ui/mir/mir_alignment_check_i686-pc-windows-msvc.rs b/tests/ui/mir/mir_alignment_check_i686-pc-windows-msvc.rs
new file mode 100644
index 00000000000..56388c1047e
--- /dev/null
+++ b/tests/ui/mir/mir_alignment_check_i686-pc-windows-msvc.rs
@@ -0,0 +1,21 @@
+// run-pass
+// only-i686-pc-windows-msvc
+// compile-flags: -Copt-level=0 -Cdebug-assertions=yes
+
+// MSVC isn't sure if on 32-bit Windows its u64 type is 8-byte-aligned or 4-byte-aligned.
+// So this test ensures that on i686-pc-windows-msvc, we do not insert a runtime check
+// that will fail on dereferencing of a pointer to u64 which is not 8-byte-aligned but is
+// 4-byte-aligned.
+
+#![feature(strict_provenance)]
+
+fn main() {
+    let mut x = [0u64; 2];
+    let ptr: *mut u8 = x.as_mut_ptr().cast::<u8>();
+    unsafe {
+        let misaligned = ptr.add(4).cast::<u64>();
+        assert!(misaligned.addr() % 8 != 0);
+        assert!(misaligned.addr() % 4 == 0);
+        *misaligned = 42;
+    }
+}