From c151ed4764636b380aab6f6edc6e369c4a7a2f58 Mon Sep 17 00:00:00 2001
From: Camille GILLOT <gillot.camille@gmail.com>
Date: Mon, 5 Feb 2024 23:19:48 +0000
Subject: [PATCH 1/2] Add test.

---
 tests/mir-opt/gvn_copy_moves.fn0.GVN.diff | 27 +++++++++++++
 tests/mir-opt/gvn_copy_moves.rs           | 46 +++++++++++++++++++++++
 2 files changed, 73 insertions(+)
 create mode 100644 tests/mir-opt/gvn_copy_moves.fn0.GVN.diff
 create mode 100644 tests/mir-opt/gvn_copy_moves.rs

diff --git a/tests/mir-opt/gvn_copy_moves.fn0.GVN.diff b/tests/mir-opt/gvn_copy_moves.fn0.GVN.diff
new file mode 100644
index 0000000000000..b7463a08d9f3f
--- /dev/null
+++ b/tests/mir-opt/gvn_copy_moves.fn0.GVN.diff
@@ -0,0 +1,27 @@
+- // MIR for `fn0` before GVN
++ // MIR for `fn0` after GVN
+  
+  fn fn0() -> () {
+      let mut _0: ();
+      let mut _1: usize;
+      let mut _2: [u128; 6];
+      let mut _3: ([u128; 6],);
+      let mut _4: ([u128; 6],);
+      let mut _5: ();
+  
+      bb0: {
+          _1 = const 1_usize;
+          _2 = [const 42_u128; 6];
+-         _2[_1] = const 1_u128;
++         _2[1 of 2] = const 1_u128;
+          _3 = (_2,);
+          _4 = _3;
+-         _5 = fn1(move (_3.0: [u128; 6]), _4) -> [return: bb1, unwind unreachable];
++         _5 = fn1(move (_3.0: [u128; 6]), _3) -> [return: bb1, unwind unreachable];
+      }
+  
+      bb1: {
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/gvn_copy_moves.rs b/tests/mir-opt/gvn_copy_moves.rs
new file mode 100644
index 0000000000000..d216825e5e689
--- /dev/null
+++ b/tests/mir-opt/gvn_copy_moves.rs
@@ -0,0 +1,46 @@
+// unit-test: GVN
+
+#![feature(custom_mir, core_intrinsics)]
+extern crate core;
+use core::intrinsics::mir::*;
+
+#[custom_mir(dialect = "runtime", phase = "initial")]
+fn fn0() {
+    // CHECK-LABEL: fn fn0(
+    mir! {
+        let a: usize;
+        let b: [u128; 6];
+        let c: ([u128; 6],);
+        let d: ([u128; 6],);
+        let x: ();
+        {
+            // CHECK: bb0: {
+            // CHECK-NEXT: _1 = const 1_usize;
+            // CHECK-NEXT: _2 = [const 42_u128; 6];
+            // CHECK-NEXT: _2[1 of 2] = const 1_u128;
+            // CHECK-NEXT: _3 = (_2,);
+            // CHECK-NEXT: _4 = _3;
+            // CHECK-NEXT: _5 = fn1((_3.0: [u128; 6]), _3)
+            a = 1_usize;
+            b = [42; 6];
+            b[a] = 1;
+            c = (b,);
+            d = c;
+            Call(x = fn1(Move(c.0), d), ReturnTo(bb1), UnwindUnreachable())
+        }
+        bb1 = {
+            Return()
+        }
+    }
+}
+
+#[inline(never)]
+fn fn1(a: [u128; 6], mut b: ([u128; 6],)) {
+    b.0 = [0; 6];
+}
+
+fn main() {
+    fn0();
+}
+
+// EMIT_MIR gvn_copy_moves.fn0.GVN.diff

From 6fbd761644932a31457b15f425f87378387fbdc1 Mon Sep 17 00:00:00 2001
From: Camille GILLOT <gillot.camille@gmail.com>
Date: Mon, 5 Feb 2024 23:21:33 +0000
Subject: [PATCH 2/2] Also turn moves into copies even if through projections.

---
 compiler/rustc_mir_transform/src/gvn.rs                     | 4 ++--
 tests/mir-opt/gvn_copy_moves.fn0.GVN.diff                   | 2 +-
 .../separate_const_switch.identity.SeparateConstSwitch.diff | 6 +++---
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/compiler/rustc_mir_transform/src/gvn.rs b/compiler/rustc_mir_transform/src/gvn.rs
index 390ec3e1a36ac..07b788526706d 100644
--- a/compiler/rustc_mir_transform/src/gvn.rs
+++ b/compiler/rustc_mir_transform/src/gvn.rs
@@ -1228,8 +1228,8 @@ impl<'tcx> MutVisitor<'tcx> for StorageRemover<'tcx> {
 
     fn visit_operand(&mut self, operand: &mut Operand<'tcx>, _: Location) {
         if let Operand::Move(place) = *operand
-            && let Some(local) = place.as_local()
-            && self.reused_locals.contains(local)
+            && !place.is_indirect_first_projection()
+            && self.reused_locals.contains(place.local)
         {
             *operand = Operand::Copy(place);
         }
diff --git a/tests/mir-opt/gvn_copy_moves.fn0.GVN.diff b/tests/mir-opt/gvn_copy_moves.fn0.GVN.diff
index b7463a08d9f3f..b12de636f58b1 100644
--- a/tests/mir-opt/gvn_copy_moves.fn0.GVN.diff
+++ b/tests/mir-opt/gvn_copy_moves.fn0.GVN.diff
@@ -17,7 +17,7 @@
           _3 = (_2,);
           _4 = _3;
 -         _5 = fn1(move (_3.0: [u128; 6]), _4) -> [return: bb1, unwind unreachable];
-+         _5 = fn1(move (_3.0: [u128; 6]), _3) -> [return: bb1, unwind unreachable];
++         _5 = fn1((_3.0: [u128; 6]), _3) -> [return: bb1, unwind unreachable];
       }
   
       bb1: {
diff --git a/tests/mir-opt/separate_const_switch.identity.SeparateConstSwitch.diff b/tests/mir-opt/separate_const_switch.identity.SeparateConstSwitch.diff
index e7280f148377c..d273161528464 100644
--- a/tests/mir-opt/separate_const_switch.identity.SeparateConstSwitch.diff
+++ b/tests/mir-opt/separate_const_switch.identity.SeparateConstSwitch.diff
@@ -66,7 +66,7 @@
           _5 = ((_2 as Break).0: std::result::Result<std::convert::Infallible, i32>);
           StorageLive(_6);
           _6 = _5;
-          _12 = move ((_5 as Err).0: i32);
+          _12 = ((_5 as Err).0: i32);
           _0 = Result::<i32, i32>::Err(_12);
           StorageDead(_6);
           StorageDead(_2);
@@ -83,7 +83,7 @@
       }
   
       bb4: {
-          _10 = move ((_1 as Err).0: i32);
+          _10 = ((_1 as Err).0: i32);
           StorageLive(_11);
           _11 = Result::<Infallible, i32>::Err(_10);
           _2 = ControlFlow::<Result<Infallible, i32>, i32>::Break(move _11);
@@ -92,7 +92,7 @@
       }
   
       bb5: {
-          _9 = move ((_1 as Ok).0: i32);
+          _9 = ((_1 as Ok).0: i32);
           _2 = ControlFlow::<Result<Infallible, i32>, i32>::Continue(_9);
           goto -> bb3;
       }