From a7d48fcc15f9f71917927144e1e1ece4f6f5e5a4 Mon Sep 17 00:00:00 2001
From: DianQK <dianqk@dianqk.net>
Date: Sun, 28 Jul 2024 13:28:44 +0800
Subject: [PATCH] Simplify some of the copy-like forms

---
 .../rustc_mir_transform/src/instsimplify.rs   |  18 +-
 ...l_copy.InstSimplify-after-simplifycfg.diff |  47 +++++
 ...t_type.InstSimplify-after-simplifycfg.diff |  46 +++++
 ...hanged.InstSimplify-after-simplifycfg.diff |  47 +++++
 ...y_move.InstSimplify-after-simplifycfg.diff |  46 +++++
 ..._ret_2.InstSimplify-after-simplifycfg.diff |  68 ++++++++
 ...hanged.InstSimplify-after-simplifycfg.diff |  53 ++++++
 ...nged_2.InstSimplify-after-simplifycfg.diff |  52 ++++++
 ...ruct_1.InstSimplify-after-simplifycfg.diff |  13 ++
 ...ruct_2.InstSimplify-after-simplifycfg.diff |  13 ++
 ...t_copy.InstSimplify-after-simplifycfg.diff |  68 ++++++++
 tests/mir-opt/instsimplify/copy_like.rs       | 160 ++++++++++++++++++
 ..._index.InstSimplify-after-simplifycfg.diff |  35 ++++
 13 files changed, 663 insertions(+), 3 deletions(-)
 create mode 100644 tests/mir-opt/instsimplify/copy_like.all_copy.InstSimplify-after-simplifycfg.diff
 create mode 100644 tests/mir-opt/instsimplify/copy_like.all_copy_different_type.InstSimplify-after-simplifycfg.diff
 create mode 100644 tests/mir-opt/instsimplify/copy_like.all_copy_has_changed.InstSimplify-after-simplifycfg.diff
 create mode 100644 tests/mir-opt/instsimplify/copy_like.all_copy_move.InstSimplify-after-simplifycfg.diff
 create mode 100644 tests/mir-opt/instsimplify/copy_like.all_copy_ret_2.InstSimplify-after-simplifycfg.diff
 create mode 100644 tests/mir-opt/instsimplify/copy_like.all_copy_use_changed.InstSimplify-after-simplifycfg.diff
 create mode 100644 tests/mir-opt/instsimplify/copy_like.all_copy_use_changed_2.InstSimplify-after-simplifycfg.diff
 create mode 100644 tests/mir-opt/instsimplify/copy_like.empty_struct_1.InstSimplify-after-simplifycfg.diff
 create mode 100644 tests/mir-opt/instsimplify/copy_like.empty_struct_2.InstSimplify-after-simplifycfg.diff
 create mode 100644 tests/mir-opt/instsimplify/copy_like.nest_copy.InstSimplify-after-simplifycfg.diff
 create mode 100644 tests/mir-opt/instsimplify/copy_like.rs
 create mode 100644 tests/mir-opt/instsimplify/copy_like.same_type_different_index.InstSimplify-after-simplifycfg.diff

diff --git a/compiler/rustc_mir_transform/src/instsimplify.rs b/compiler/rustc_mir_transform/src/instsimplify.rs
index 51bc648bf95a9..c84fb32992bbe 100644
--- a/compiler/rustc_mir_transform/src/instsimplify.rs
+++ b/compiler/rustc_mir_transform/src/instsimplify.rs
@@ -265,8 +265,18 @@ impl<'tcx> InstSimplifyContext<'tcx, '_> {
                     }
                     // Collect available assignments, including those transformed from `Aggregate`.
                     if let Some(local) = dest.as_local() {
-                        assignments[local] = if let Rvalue::Use(Operand::Copy(place)) = rvalue {
-                            Some(*place)
+                        assignments[local] = if let Rvalue::Use(operand) = rvalue
+                            && let Some(place) = operand.place()
+                        {
+                            if let Some(rvalue_local) = place.as_local() {
+                                let place = assignments[rvalue_local];
+                                if operand.is_move() {
+                                    assignments[rvalue_local] = None;
+                                }
+                                place
+                            } else {
+                                Some(place)
+                            }
                         } else {
                             // This assignment generally comes from debuginfo (e.g., Ref),
                             // but we still need to check if a local is being overridden.
@@ -277,7 +287,9 @@ impl<'tcx> InstSimplifyContext<'tcx, '_> {
                         assignments.reset_all(None);
                     }
                 }
-                StatementKind::StorageLive(_) | StatementKind::StorageDead(_) => {}
+                StatementKind::StorageLive(_)
+                | StatementKind::StorageDead(_)
+                | StatementKind::Nop => {}
                 _ => {
                     assignments.reset_all(None);
                 }
diff --git a/tests/mir-opt/instsimplify/copy_like.all_copy.InstSimplify-after-simplifycfg.diff b/tests/mir-opt/instsimplify/copy_like.all_copy.InstSimplify-after-simplifycfg.diff
new file mode 100644
index 0000000000000..0f0408cc4c1e9
--- /dev/null
+++ b/tests/mir-opt/instsimplify/copy_like.all_copy.InstSimplify-after-simplifycfg.diff
@@ -0,0 +1,47 @@
+- // MIR for `all_copy` before InstSimplify-after-simplifycfg
++ // MIR for `all_copy` after InstSimplify-after-simplifycfg
+  
+  fn all_copy(_1: &AllCopy) -> AllCopy {
+      debug v => _1;
+      let mut _0: AllCopy;
+      let _2: i32;
+      let mut _5: i32;
+      let mut _6: u64;
+      let mut _7: [i8; 3];
+      scope 1 {
+          debug a => _2;
+          let _3: u64;
+          scope 2 {
+              debug b => _3;
+              let _4: [i8; 3];
+              scope 3 {
+                  debug c => _4;
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_2);
+          _2 = ((*_1).0: i32);
+          StorageLive(_3);
+          _3 = ((*_1).1: u64);
+          StorageLive(_4);
+          _4 = ((*_1).2: [i8; 3]);
+          StorageLive(_5);
+          _5 = _2;
+          StorageLive(_6);
+          _6 = _3;
+          StorageLive(_7);
+          _7 = _4;
+-         _0 = AllCopy { a: move _5, b: move _6, c: move _7 };
++         _0 = (*_1);
+          StorageDead(_7);
+          StorageDead(_6);
+          StorageDead(_5);
+          StorageDead(_4);
+          StorageDead(_3);
+          StorageDead(_2);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/instsimplify/copy_like.all_copy_different_type.InstSimplify-after-simplifycfg.diff b/tests/mir-opt/instsimplify/copy_like.all_copy_different_type.InstSimplify-after-simplifycfg.diff
new file mode 100644
index 0000000000000..5bbe3328fbb53
--- /dev/null
+++ b/tests/mir-opt/instsimplify/copy_like.all_copy_different_type.InstSimplify-after-simplifycfg.diff
@@ -0,0 +1,46 @@
+- // MIR for `all_copy_different_type` before InstSimplify-after-simplifycfg
++ // MIR for `all_copy_different_type` after InstSimplify-after-simplifycfg
+  
+  fn all_copy_different_type(_1: &AllCopy) -> AllCopy2 {
+      debug v => _1;
+      let mut _0: AllCopy2;
+      let _2: i32;
+      let mut _5: i32;
+      let mut _6: u64;
+      let mut _7: [i8; 3];
+      scope 1 {
+          debug a => _2;
+          let _3: u64;
+          scope 2 {
+              debug b => _3;
+              let _4: [i8; 3];
+              scope 3 {
+                  debug c => _4;
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_2);
+          _2 = ((*_1).0: i32);
+          StorageLive(_3);
+          _3 = ((*_1).1: u64);
+          StorageLive(_4);
+          _4 = ((*_1).2: [i8; 3]);
+          StorageLive(_5);
+          _5 = _2;
+          StorageLive(_6);
+          _6 = _3;
+          StorageLive(_7);
+          _7 = _4;
+          _0 = AllCopy2 { a: move _5, b: move _6, c: move _7 };
+          StorageDead(_7);
+          StorageDead(_6);
+          StorageDead(_5);
+          StorageDead(_4);
+          StorageDead(_3);
+          StorageDead(_2);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/instsimplify/copy_like.all_copy_has_changed.InstSimplify-after-simplifycfg.diff b/tests/mir-opt/instsimplify/copy_like.all_copy_has_changed.InstSimplify-after-simplifycfg.diff
new file mode 100644
index 0000000000000..037c114da0318
--- /dev/null
+++ b/tests/mir-opt/instsimplify/copy_like.all_copy_has_changed.InstSimplify-after-simplifycfg.diff
@@ -0,0 +1,47 @@
+- // MIR for `all_copy_has_changed` before InstSimplify-after-simplifycfg
++ // MIR for `all_copy_has_changed` after InstSimplify-after-simplifycfg
+  
+  fn all_copy_has_changed(_1: &mut AllCopy) -> AllCopy {
+      debug v => _1;
+      let mut _0: AllCopy;
+      let _2: i32;
+      let mut _5: i32;
+      let mut _6: u64;
+      let mut _7: [i8; 3];
+      scope 1 {
+          debug a => _2;
+          let _3: u64;
+          scope 2 {
+              debug b => _3;
+              let _4: [i8; 3];
+              scope 3 {
+                  debug c => _4;
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_2);
+          _2 = ((*_1).0: i32);
+          StorageLive(_3);
+          _3 = ((*_1).1: u64);
+          StorageLive(_4);
+          _4 = ((*_1).2: [i8; 3]);
+          ((*_1).0: i32) = const 1_i32;
+          StorageLive(_5);
+          _5 = _2;
+          StorageLive(_6);
+          _6 = _3;
+          StorageLive(_7);
+          _7 = _4;
+          _0 = AllCopy { a: move _5, b: move _6, c: move _7 };
+          StorageDead(_7);
+          StorageDead(_6);
+          StorageDead(_5);
+          StorageDead(_4);
+          StorageDead(_3);
+          StorageDead(_2);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/instsimplify/copy_like.all_copy_move.InstSimplify-after-simplifycfg.diff b/tests/mir-opt/instsimplify/copy_like.all_copy_move.InstSimplify-after-simplifycfg.diff
new file mode 100644
index 0000000000000..0fde7c3d4e53b
--- /dev/null
+++ b/tests/mir-opt/instsimplify/copy_like.all_copy_move.InstSimplify-after-simplifycfg.diff
@@ -0,0 +1,46 @@
+- // MIR for `all_copy_move` before InstSimplify-after-simplifycfg
++ // MIR for `all_copy_move` after InstSimplify-after-simplifycfg
+  
+  fn all_copy_move(_1: AllCopy) -> AllCopy {
+      debug v => _1;
+      let mut _0: AllCopy;
+      let _2: i32;
+      let mut _5: i32;
+      let mut _6: u64;
+      let mut _7: [i8; 3];
+      scope 1 {
+          debug a => _2;
+          let _3: u64;
+          scope 2 {
+              debug b => _3;
+              let _4: [i8; 3];
+              scope 3 {
+                  debug c => _4;
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_2);
+          _2 = (_1.0: i32);
+          StorageLive(_3);
+          _3 = (_1.1: u64);
+          StorageLive(_4);
+          _4 = (_1.2: [i8; 3]);
+          StorageLive(_5);
+          _5 = _2;
+          StorageLive(_6);
+          _6 = _3;
+          StorageLive(_7);
+          _7 = _4;
+          _0 = AllCopy { a: move _5, b: move _6, c: move _7 };
+          StorageDead(_7);
+          StorageDead(_6);
+          StorageDead(_5);
+          StorageDead(_4);
+          StorageDead(_3);
+          StorageDead(_2);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/instsimplify/copy_like.all_copy_ret_2.InstSimplify-after-simplifycfg.diff b/tests/mir-opt/instsimplify/copy_like.all_copy_ret_2.InstSimplify-after-simplifycfg.diff
new file mode 100644
index 0000000000000..f6c91b6535fed
--- /dev/null
+++ b/tests/mir-opt/instsimplify/copy_like.all_copy_ret_2.InstSimplify-after-simplifycfg.diff
@@ -0,0 +1,68 @@
+- // MIR for `all_copy_ret_2` before InstSimplify-after-simplifycfg
++ // MIR for `all_copy_ret_2` after InstSimplify-after-simplifycfg
+  
+  fn all_copy_ret_2(_1: &AllCopy) -> (AllCopy, AllCopy) {
+      debug v => _1;
+      let mut _0: (AllCopy, AllCopy);
+      let _2: i32;
+      let mut _5: AllCopy;
+      let mut _6: i32;
+      let mut _7: u64;
+      let mut _8: [i8; 3];
+      let mut _9: AllCopy;
+      let mut _10: i32;
+      let mut _11: u64;
+      let mut _12: [i8; 3];
+      scope 1 {
+          debug a => _2;
+          let _3: u64;
+          scope 2 {
+              debug b => _3;
+              let _4: [i8; 3];
+              scope 3 {
+                  debug c => _4;
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_2);
+          _2 = ((*_1).0: i32);
+          StorageLive(_3);
+          _3 = ((*_1).1: u64);
+          StorageLive(_4);
+          _4 = ((*_1).2: [i8; 3]);
+          StorageLive(_5);
+          StorageLive(_6);
+          _6 = _2;
+          StorageLive(_7);
+          _7 = _3;
+          StorageLive(_8);
+          _8 = _4;
+-         _5 = AllCopy { a: move _6, b: move _7, c: move _8 };
++         _5 = (*_1);
+          StorageDead(_8);
+          StorageDead(_7);
+          StorageDead(_6);
+          StorageLive(_9);
+          StorageLive(_10);
+          _10 = _2;
+          StorageLive(_11);
+          _11 = _3;
+          StorageLive(_12);
+          _12 = _4;
+-         _9 = AllCopy { a: move _10, b: move _11, c: move _12 };
++         _9 = (*_1);
+          StorageDead(_12);
+          StorageDead(_11);
+          StorageDead(_10);
+          _0 = (move _5, move _9);
+          StorageDead(_9);
+          StorageDead(_5);
+          StorageDead(_4);
+          StorageDead(_3);
+          StorageDead(_2);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/instsimplify/copy_like.all_copy_use_changed.InstSimplify-after-simplifycfg.diff b/tests/mir-opt/instsimplify/copy_like.all_copy_use_changed.InstSimplify-after-simplifycfg.diff
new file mode 100644
index 0000000000000..b7ea5b62eb0f0
--- /dev/null
+++ b/tests/mir-opt/instsimplify/copy_like.all_copy_use_changed.InstSimplify-after-simplifycfg.diff
@@ -0,0 +1,53 @@
+- // MIR for `all_copy_use_changed` before InstSimplify-after-simplifycfg
++ // MIR for `all_copy_use_changed` after InstSimplify-after-simplifycfg
+  
+  fn all_copy_use_changed(_1: &mut AllCopy) -> AllCopy {
+      debug v => _1;
+      let mut _0: AllCopy;
+      let mut _2: i32;
+      let mut _3: i32;
+      let mut _6: i32;
+      let mut _7: u64;
+      let mut _8: [i8; 3];
+      scope 1 {
+          debug a => _2;
+          let _4: u64;
+          scope 2 {
+              debug b => _4;
+              let _5: [i8; 3];
+              scope 3 {
+                  debug c => _5;
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_2);
+          _2 = ((*_1).0: i32);
+          ((*_1).0: i32) = const 1_i32;
+          StorageLive(_3);
+          _3 = ((*_1).0: i32);
+          _2 = move _3;
+          StorageDead(_3);
+          StorageLive(_4);
+          _4 = ((*_1).1: u64);
+          StorageLive(_5);
+          _5 = ((*_1).2: [i8; 3]);
+          StorageLive(_6);
+          _6 = _2;
+          StorageLive(_7);
+          _7 = _4;
+          StorageLive(_8);
+          _8 = _5;
+-         _0 = AllCopy { a: move _6, b: move _7, c: move _8 };
++         _0 = (*_1);
+          StorageDead(_8);
+          StorageDead(_7);
+          StorageDead(_6);
+          StorageDead(_5);
+          StorageDead(_4);
+          StorageDead(_2);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/instsimplify/copy_like.all_copy_use_changed_2.InstSimplify-after-simplifycfg.diff b/tests/mir-opt/instsimplify/copy_like.all_copy_use_changed_2.InstSimplify-after-simplifycfg.diff
new file mode 100644
index 0000000000000..c1a2e6c977623
--- /dev/null
+++ b/tests/mir-opt/instsimplify/copy_like.all_copy_use_changed_2.InstSimplify-after-simplifycfg.diff
@@ -0,0 +1,52 @@
+- // MIR for `all_copy_use_changed_2` before InstSimplify-after-simplifycfg
++ // MIR for `all_copy_use_changed_2` after InstSimplify-after-simplifycfg
+  
+  fn all_copy_use_changed_2(_1: &mut AllCopy) -> AllCopy {
+      debug v => _1;
+      let mut _0: AllCopy;
+      let mut _2: i32;
+      let mut _5: i32;
+      let mut _6: i32;
+      let mut _7: u64;
+      let mut _8: [i8; 3];
+      scope 1 {
+          debug a => _2;
+          let _3: u64;
+          scope 2 {
+              debug b => _3;
+              let _4: [i8; 3];
+              scope 3 {
+                  debug c => _4;
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_2);
+          _2 = ((*_1).0: i32);
+          StorageLive(_3);
+          _3 = ((*_1).1: u64);
+          StorageLive(_4);
+          _4 = ((*_1).2: [i8; 3]);
+          ((*_1).0: i32) = const 1_i32;
+          StorageLive(_5);
+          _5 = ((*_1).0: i32);
+          _2 = move _5;
+          StorageDead(_5);
+          StorageLive(_6);
+          _6 = _2;
+          StorageLive(_7);
+          _7 = _3;
+          StorageLive(_8);
+          _8 = _4;
+          _0 = AllCopy { a: move _6, b: move _7, c: move _8 };
+          StorageDead(_8);
+          StorageDead(_7);
+          StorageDead(_6);
+          StorageDead(_4);
+          StorageDead(_3);
+          StorageDead(_2);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/instsimplify/copy_like.empty_struct_1.InstSimplify-after-simplifycfg.diff b/tests/mir-opt/instsimplify/copy_like.empty_struct_1.InstSimplify-after-simplifycfg.diff
new file mode 100644
index 0000000000000..e39dec643fa2a
--- /dev/null
+++ b/tests/mir-opt/instsimplify/copy_like.empty_struct_1.InstSimplify-after-simplifycfg.diff
@@ -0,0 +1,13 @@
+- // MIR for `empty_struct_1` before InstSimplify-after-simplifycfg
++ // MIR for `empty_struct_1` after InstSimplify-after-simplifycfg
+  
+  fn empty_struct_1(_1: &EmptyStruct1) -> EmptyStruct1 {
+      debug v => _1;
+      let mut _0: EmptyStruct1;
+  
+      bb0: {
+          _0 = EmptyStruct1;
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/instsimplify/copy_like.empty_struct_2.InstSimplify-after-simplifycfg.diff b/tests/mir-opt/instsimplify/copy_like.empty_struct_2.InstSimplify-after-simplifycfg.diff
new file mode 100644
index 0000000000000..fbf2b0133f5ed
--- /dev/null
+++ b/tests/mir-opt/instsimplify/copy_like.empty_struct_2.InstSimplify-after-simplifycfg.diff
@@ -0,0 +1,13 @@
+- // MIR for `empty_struct_2` before InstSimplify-after-simplifycfg
++ // MIR for `empty_struct_2` after InstSimplify-after-simplifycfg
+  
+  fn empty_struct_2(_1: &EmptyStruct2) -> EmptyStruct2 {
+      debug v => _1;
+      let mut _0: EmptyStruct2;
+  
+      bb0: {
+          _0 = EmptyStruct2;
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/instsimplify/copy_like.nest_copy.InstSimplify-after-simplifycfg.diff b/tests/mir-opt/instsimplify/copy_like.nest_copy.InstSimplify-after-simplifycfg.diff
new file mode 100644
index 0000000000000..aba8b651be31a
--- /dev/null
+++ b/tests/mir-opt/instsimplify/copy_like.nest_copy.InstSimplify-after-simplifycfg.diff
@@ -0,0 +1,68 @@
+- // MIR for `nest_copy` before InstSimplify-after-simplifycfg
++ // MIR for `nest_copy` after InstSimplify-after-simplifycfg
+  
+  fn nest_copy(_1: &NestCopy) -> NestCopy {
+      debug v => _1;
+      let mut _0: NestCopy;
+      let _2: i32;
+      let mut _6: i32;
+      let mut _7: u64;
+      let mut _8: [i8; 3];
+      let mut _10: i32;
+      let mut _11: AllCopy;
+      scope 1 {
+          debug a => _2;
+          let _3: u64;
+          scope 2 {
+              debug b => _3;
+              let _4: [i8; 3];
+              scope 3 {
+                  debug c => _4;
+                  let _5: AllCopy;
+                  scope 4 {
+                      debug all_copy => _5;
+                      let _9: i32;
+                      scope 5 {
+                          debug d => _9;
+                      }
+                  }
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_2);
+          _2 = (((*_1).1: AllCopy).0: i32);
+          StorageLive(_3);
+          _3 = (((*_1).1: AllCopy).1: u64);
+          StorageLive(_4);
+          _4 = (((*_1).1: AllCopy).2: [i8; 3]);
+          StorageLive(_5);
+          StorageLive(_6);
+          _6 = _2;
+          StorageLive(_7);
+          _7 = _3;
+          StorageLive(_8);
+          _8 = _4;
+          _5 = AllCopy { a: move _6, b: move _7, c: move _8 };
+          StorageDead(_8);
+          StorageDead(_7);
+          StorageDead(_6);
+          StorageLive(_9);
+          _9 = ((*_1).0: i32);
+          StorageLive(_10);
+          _10 = _9;
+          StorageLive(_11);
+          _11 = move _5;
+          _0 = NestCopy { d: move _10, all_copy: move _11 };
+          StorageDead(_11);
+          StorageDead(_10);
+          StorageDead(_9);
+          StorageDead(_5);
+          StorageDead(_4);
+          StorageDead(_3);
+          StorageDead(_2);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/instsimplify/copy_like.rs b/tests/mir-opt/instsimplify/copy_like.rs
new file mode 100644
index 0000000000000..143474d0f0c6f
--- /dev/null
+++ b/tests/mir-opt/instsimplify/copy_like.rs
@@ -0,0 +1,160 @@
+//@ test-mir-pass: InstSimplify-after-simplifycfg
+
+struct AllCopy {
+    a: i32,
+    b: u64,
+    c: [i8; 3],
+}
+
+// EMIT_MIR copy_like.all_copy.InstSimplify-after-simplifycfg.diff
+fn all_copy(v: &AllCopy) -> AllCopy {
+    // CHECK-LABEL: fn all_copy(
+    // CHECK: bb0: {
+    // CHECK-NOT: = AllCopy { {{.*}} };
+    // CHECK: _0 = (*_1);
+    let a = v.a;
+    let b = v.b;
+    let c = v.c;
+    AllCopy { a, b, c }
+}
+
+// FIXME: This can be transformed into `Copy`.
+// EMIT_MIR copy_like.all_copy_move.InstSimplify-after-simplifycfg.diff
+fn all_copy_move(v: AllCopy) -> AllCopy {
+    // CHECK-LABEL: fn all_copy_move(
+    // CHECK: bb0: {
+    // CHECK-NOT: _0 = (*_1);
+    // CHECK: = AllCopy { {{.*}} };
+    let a = v.a;
+    let b = v.b;
+    let c = v.c;
+    AllCopy { a, b, c }
+}
+
+// EMIT_MIR copy_like.all_copy_ret_2.InstSimplify-after-simplifycfg.diff
+fn all_copy_ret_2(v: &AllCopy) -> (AllCopy, AllCopy) {
+    // CHECK-LABEL: fn all_copy_ret_2(
+    // CHECK: bb0: {
+    // CHECK-NOT: = AllCopy { {{.*}} };
+    // CHECK: [[V1:_.*]] = (*_1);
+    // CHECK: [[V2:_.*]] = (*_1);
+    // CHECK: _0 = (move [[V1]], move [[V2]]);
+    let a = v.a;
+    let b = v.b;
+    let c = v.c;
+    (AllCopy { a, b, c }, AllCopy { a, b, c })
+}
+
+struct AllCopy2 {
+    a: i32,
+    b: u64,
+    c: [i8; 3],
+}
+
+// EMIT_MIR copy_like.all_copy_different_type.InstSimplify-after-simplifycfg.diff
+fn all_copy_different_type(v: &AllCopy) -> AllCopy2 {
+    // CHECK-LABEL: fn all_copy_different_type(
+    // CHECK: bb0: {
+    // CHECK: _0 = AllCopy2 { {{.*}} };
+    let a = v.a;
+    let b = v.b;
+    let c = v.c;
+    AllCopy2 { a, b, c }
+}
+
+struct SameType {
+    a: i32,
+    b: i32,
+}
+
+// EMIT_MIR copy_like.same_type_different_index.InstSimplify-after-simplifycfg.diff
+fn same_type_different_index(v: &SameType) -> SameType {
+    // CHECK-LABEL: fn same_type_different_index(
+    // CHECK: bb0: {
+    // CHECK: _0 = SameType { {{.*}} };
+    let a = v.b;
+    let b = v.a;
+    SameType { a, b }
+}
+
+// EMIT_MIR copy_like.all_copy_has_changed.InstSimplify-after-simplifycfg.diff
+fn all_copy_has_changed(v: &mut AllCopy) -> AllCopy {
+    // CHECK-LABEL: fn all_copy_has_changed(
+    // CHECK: bb0: {
+    // CHECK: _0 = AllCopy { {{.*}} };
+    let a = v.a;
+    let b = v.b;
+    let c = v.c;
+    v.a = 1;
+    AllCopy { a, b, c }
+}
+
+// EMIT_MIR copy_like.all_copy_use_changed.InstSimplify-after-simplifycfg.diff
+fn all_copy_use_changed(v: &mut AllCopy) -> AllCopy {
+    // CHECK-LABEL: fn all_copy_use_changed(
+    // CHECK: bb0: {
+    // CHECK-NOT: = AllCopy { {{.*}} };
+    // CHECK: _0 = (*_1);
+    let mut a = v.a;
+    v.a = 1;
+    a = v.a;
+    let b = v.b;
+    let c = v.c;
+    AllCopy { a, b, c }
+}
+
+// We deleted the records for b and c,
+// because we couldn't easily determine which field had been updated.
+// EMIT_MIR copy_like.all_copy_use_changed_2.InstSimplify-after-simplifycfg.diff
+fn all_copy_use_changed_2(v: &mut AllCopy) -> AllCopy {
+    // CHECK-LABEL: fn all_copy_use_changed_2(
+    // CHECK: bb0: {
+    // CHECK-NOT: _0 = (*_1);
+    // CHECK: = AllCopy { {{.*}} };
+    let mut a = v.a;
+    let b = v.b;
+    let c = v.c;
+    v.a = 1;
+    a = v.a;
+    AllCopy { a, b, c }
+}
+
+struct NestCopy {
+    d: i32,
+    all_copy: AllCopy,
+}
+
+// FIXME: Consider supporting multi-level fields?
+// (Note: clone becomes a single-level field after inlining)
+// EMIT_MIR copy_like.nest_copy.InstSimplify-after-simplifycfg.diff
+fn nest_copy(v: &NestCopy) -> NestCopy {
+    // CHECK-LABEL: fn nest_copy(
+    // CHECK: bb0: {
+    // CHECK: = AllCopy { {{.*}} };
+    // CHECK: = NestCopy { {{.*}} };
+    let a = v.all_copy.a;
+    let b = v.all_copy.b;
+    let c = v.all_copy.c;
+    let all_copy = AllCopy { a, b, c };
+    let d = v.d;
+    NestCopy { d, all_copy }
+}
+
+struct EmptyStruct1;
+struct EmptyStruct2 {}
+
+// EMIT_MIR copy_like.empty_struct_1.InstSimplify-after-simplifycfg.diff
+fn empty_struct_1(v: &EmptyStruct1) -> EmptyStruct1 {
+    // CHECK-LABEL: fn empty_struct_1(
+    // CHECK: bb0: {
+    // CHECK: _0 = EmptyStruct1;
+    EmptyStruct1
+}
+
+// EMIT_MIR copy_like.empty_struct_2.InstSimplify-after-simplifycfg.diff
+fn empty_struct_2(v: &EmptyStruct2) -> EmptyStruct2 {
+    // CHECK-LABEL: fn empty_struct_2(
+    // CHECK: bb0: {
+    // CHECK: _0 = EmptyStruct2;
+    EmptyStruct2 {}
+}
diff --git a/tests/mir-opt/instsimplify/copy_like.same_type_different_index.InstSimplify-after-simplifycfg.diff b/tests/mir-opt/instsimplify/copy_like.same_type_different_index.InstSimplify-after-simplifycfg.diff
new file mode 100644
index 0000000000000..4e53266bc42bc
--- /dev/null
+++ b/tests/mir-opt/instsimplify/copy_like.same_type_different_index.InstSimplify-after-simplifycfg.diff
@@ -0,0 +1,35 @@
+- // MIR for `same_type_different_index` before InstSimplify-after-simplifycfg
++ // MIR for `same_type_different_index` after InstSimplify-after-simplifycfg
+  
+  fn same_type_different_index(_1: &SameType) -> SameType {
+      debug v => _1;
+      let mut _0: SameType;
+      let _2: i32;
+      let mut _4: i32;
+      let mut _5: i32;
+      scope 1 {
+          debug a => _2;
+          let _3: i32;
+          scope 2 {
+              debug b => _3;
+          }
+      }
+  
+      bb0: {
+          StorageLive(_2);
+          _2 = ((*_1).1: i32);
+          StorageLive(_3);
+          _3 = ((*_1).0: i32);
+          StorageLive(_4);
+          _4 = _2;
+          StorageLive(_5);
+          _5 = _3;
+          _0 = SameType { a: move _4, b: move _5 };
+          StorageDead(_5);
+          StorageDead(_4);
+          StorageDead(_3);
+          StorageDead(_2);
+          return;
+      }
+  }
+