From 7585786ecb24e7cc3eaad08a6706ae3fb8e63ea8 Mon Sep 17 00:00:00 2001
From: Scott McMurray <scottmcm@users.noreply.github.com>
Date: Sat, 14 Feb 2026 17:58:44 -0800
Subject: [PATCH] Add a mir-opt test for alignment check generation

---
 tests/mir-opt/alignment_checks.rs             | 19 +++++++++++++
 ....sized_ptr.CheckAlignment.panic-abort.diff | 27 +++++++++++++++++++
 ...sized_ptr.CheckAlignment.panic-unwind.diff | 27 +++++++++++++++++++
 3 files changed, 73 insertions(+)
 create mode 100644 tests/mir-opt/alignment_checks.rs
 create mode 100644 tests/mir-opt/alignment_checks.sized_ptr.CheckAlignment.panic-abort.diff
 create mode 100644 tests/mir-opt/alignment_checks.sized_ptr.CheckAlignment.panic-unwind.diff

diff --git a/tests/mir-opt/alignment_checks.rs b/tests/mir-opt/alignment_checks.rs
new file mode 100644
index 000000000000..6f1329cb4e64
--- /dev/null
+++ b/tests/mir-opt/alignment_checks.rs
@@ -0,0 +1,19 @@
+//@ compile-flags: -Copt-level=1 -Zmir-opt-level=2 -Zub-checks
+//@ only-64bit
+// EMIT_MIR_FOR_EACH_PANIC_STRATEGY
+
+#![crate_type = "lib"]
+
+// The diff shows exactly what is generated by the pass;
+// then we check the final `-O1` output for people who want to run them
+// without the codegen being too terrible.
+
+// EMIT_MIR alignment_checks.sized_ptr.CheckAlignment.diff
+pub unsafe fn sized_ptr(ptr: *const u32) -> u32 {
+    // CHECK-LABEL: fn sized_ptr(_1: *const u32)
+    // CHECK: _2 = copy _1 as usize (Transmute);
+    // CHECK: _3 = BitAnd(copy _2, const 3_usize);
+    // CHECK: _4 = Eq(copy _3, const 0_usize);
+    // CHECK: assert(copy _4,
+    *ptr
+}
diff --git a/tests/mir-opt/alignment_checks.sized_ptr.CheckAlignment.panic-abort.diff b/tests/mir-opt/alignment_checks.sized_ptr.CheckAlignment.panic-abort.diff
new file mode 100644
index 000000000000..c383975d9c0f
--- /dev/null
+++ b/tests/mir-opt/alignment_checks.sized_ptr.CheckAlignment.panic-abort.diff
@@ -0,0 +1,27 @@
+- // MIR for `sized_ptr` before CheckAlignment
++ // MIR for `sized_ptr` after CheckAlignment
+  
+  fn sized_ptr(_1: *const u32) -> u32 {
+      debug ptr => _1;
+      let mut _0: u32;
++     let mut _2: *const ();
++     let mut _3: usize;
++     let mut _4: usize;
++     let mut _5: usize;
++     let mut _6: bool;
+  
+      bb0: {
++         _2 = copy _1 as *const () (PtrToPtr);
++         _3 = copy _2 as usize (Transmute);
++         _4 = Sub(const <u32 as std::mem::SizedTypeProperties>::ALIGN, const 1_usize);
++         _5 = BitAnd(copy _3, copy _4);
++         _6 = Eq(copy _5, const 0_usize);
++         assert(copy _6, "misaligned pointer dereference: address must be a multiple of {} but is {}", const <u32 as std::mem::SizedTypeProperties>::ALIGN, copy _3) -> [success: bb1, unwind unreachable];
++     }
++ 
++     bb1: {
+          _0 = copy (*_1);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/alignment_checks.sized_ptr.CheckAlignment.panic-unwind.diff b/tests/mir-opt/alignment_checks.sized_ptr.CheckAlignment.panic-unwind.diff
new file mode 100644
index 000000000000..c383975d9c0f
--- /dev/null
+++ b/tests/mir-opt/alignment_checks.sized_ptr.CheckAlignment.panic-unwind.diff
@@ -0,0 +1,27 @@
+- // MIR for `sized_ptr` before CheckAlignment
++ // MIR for `sized_ptr` after CheckAlignment
+  
+  fn sized_ptr(_1: *const u32) -> u32 {
+      debug ptr => _1;
+      let mut _0: u32;
++     let mut _2: *const ();
++     let mut _3: usize;
++     let mut _4: usize;
++     let mut _5: usize;
++     let mut _6: bool;
+  
+      bb0: {
++         _2 = copy _1 as *const () (PtrToPtr);
++         _3 = copy _2 as usize (Transmute);
++         _4 = Sub(const <u32 as std::mem::SizedTypeProperties>::ALIGN, const 1_usize);
++         _5 = BitAnd(copy _3, copy _4);
++         _6 = Eq(copy _5, const 0_usize);
++         assert(copy _6, "misaligned pointer dereference: address must be a multiple of {} but is {}", const <u32 as std::mem::SizedTypeProperties>::ALIGN, copy _3) -> [success: bb1, unwind unreachable];
++     }
++ 
++     bb1: {
+          _0 = copy (*_1);
+          return;
+      }
+  }
+