From 5c1cb5bbc6532c114ee509db7458ebe4967153da Mon Sep 17 00:00:00 2001
From: Camille GILLOT <gillot.camille@gmail.com>
Date: Sat, 4 Feb 2023 11:48:28 +0000
Subject: [PATCH 1/2] Turn projections into copies in CopyProp.
---
compiler/rustc_mir_transform/src/copy_prop.rs | 4 +--
.../copy-prop/move_projection.f.CopyProp.diff | 31 +++++++++++++++++
tests/mir-opt/copy-prop/move_projection.rs | 34 +++++++++++++++++++
..._option_map_e2e.ezmap.PreCodegen.after.mir | 2 +-
4 files changed, 68 insertions(+), 3 deletions(-)
create mode 100644 tests/mir-opt/copy-prop/move_projection.f.CopyProp.diff
create mode 100644 tests/mir-opt/copy-prop/move_projection.rs
diff --git a/compiler/rustc_mir_transform/src/copy_prop.rs b/compiler/rustc_mir_transform/src/copy_prop.rs
index 4c7d45be0753e..8f16df93a56d1 100644
--- a/compiler/rustc_mir_transform/src/copy_prop.rs
+++ b/compiler/rustc_mir_transform/src/copy_prop.rs
@@ -153,8 +153,8 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'_, 'tcx> {
fn visit_operand(&mut self, operand: &mut Operand<'tcx>, loc: Location) {
if let Operand::Move(place) = *operand
- && let Some(local) = place.as_local()
- && !self.fully_moved.contains(local)
+ && !place.has_deref()
+ && !self.fully_moved.contains(place.local)
{
*operand = Operand::Copy(place);
}
diff --git a/tests/mir-opt/copy-prop/move_projection.f.CopyProp.diff b/tests/mir-opt/copy-prop/move_projection.f.CopyProp.diff
new file mode 100644
index 0000000000000..02308beb88af2
--- /dev/null
+++ b/tests/mir-opt/copy-prop/move_projection.f.CopyProp.diff
@@ -0,0 +1,31 @@
+- // MIR for `f` before CopyProp
++ // MIR for `f` after CopyProp
+
+ fn f(_1: Foo) -> bool {
+ let mut _0: bool; // return place in scope 0 at $DIR/move_projection.rs:+0:17: +0:21
+ let mut _2: Foo; // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+ let mut _3: u8; // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+
+ bb0: {
+- _2 = _1; // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+- _3 = move (_2.0: u8); // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+- _0 = opaque::<Foo>(move _1) -> bb1; // scope 0 at $DIR/move_projection.rs:+6:13: +6:44
++ _3 = (_1.0: u8); // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
++ _0 = opaque::<Foo>(_1) -> bb1; // scope 0 at $DIR/move_projection.rs:+6:13: +6:44
+ // mir::Constant
+ // + span: $DIR/move_projection.rs:19:28: 19:34
+ // + literal: Const { ty: fn(Foo) -> bool {opaque::<Foo>}, val: Value(<ZST>) }
+ }
+
+ bb1: {
+ _0 = opaque::<u8>(move _3) -> bb2; // scope 0 at $DIR/move_projection.rs:+9:13: +9:44
+ // mir::Constant
+ // + span: $DIR/move_projection.rs:22:28: 22:34
+ // + literal: Const { ty: fn(u8) -> bool {opaque::<u8>}, val: Value(<ZST>) }
+ }
+
+ bb2: {
+ return; // scope 0 at $DIR/move_projection.rs:+12:13: +12:21
+ }
+ }
+
diff --git a/tests/mir-opt/copy-prop/move_projection.rs b/tests/mir-opt/copy-prop/move_projection.rs
new file mode 100644
index 0000000000000..2a1bbae99a4c8
--- /dev/null
+++ b/tests/mir-opt/copy-prop/move_projection.rs
@@ -0,0 +1,34 @@
+// unit-test: CopyProp
+
+#![feature(custom_mir, core_intrinsics)]
+#![allow(unused_assignments)]
+extern crate core;
+use core::intrinsics::mir::*;
+
+fn opaque(_: impl Sized) -> bool { true }
+
+struct Foo(u8);
+
+#[custom_mir(dialect = "analysis", phase = "post-cleanup")]
+fn f(a: Foo) -> bool {
+ mir!(
+ {
+ let b = a;
+ // This is a move out of a copy, so must become a copy of `a.0`.
+ let c = Move(b.0);
+ Call(RET, bb1, opaque(Move(a)))
+ }
+ bb1 = {
+ Call(RET, ret, opaque(Move(c)))
+ }
+ ret = {
+ Return()
+ }
+ )
+}
+
+fn main() {
+ assert!(f(Foo(0)));
+}
+
+// EMIT_MIR move_projection.f.CopyProp.diff
diff --git a/tests/mir-opt/simple_option_map_e2e.ezmap.PreCodegen.after.mir b/tests/mir-opt/simple_option_map_e2e.ezmap.PreCodegen.after.mir
index 5c898d798ff16..69d12bc2d5394 100644
--- a/tests/mir-opt/simple_option_map_e2e.ezmap.PreCodegen.after.mir
+++ b/tests/mir-opt/simple_option_map_e2e.ezmap.PreCodegen.after.mir
@@ -37,7 +37,7 @@ fn ezmap(_1: Option<i32>) -> Option<i32> {
}
bb3: {
- _4 = move ((_1 as Some).0: i32); // scope 1 at $DIR/simple_option_map_e2e.rs:7:14: 7:15
+ _4 = ((_1 as Some).0: i32); // scope 1 at $DIR/simple_option_map_e2e.rs:7:14: 7:15
StorageLive(_5); // scope 2 at $DIR/simple_option_map_e2e.rs:7:25: 7:29
StorageLive(_6); // scope 2 at $DIR/simple_option_map_e2e.rs:7:25: 7:29
_6 = (move _4,); // scope 2 at $DIR/simple_option_map_e2e.rs:7:25: 7:29
From 9c5add14e7c1695bc018a941c383f01a7dde8730 Mon Sep 17 00:00:00 2001
From: Camille Gillot <gillot.camille@gmail.com>
Date: Mon, 6 Feb 2023 18:14:24 +0100
Subject: [PATCH 2/2] Comment move->copy transform.
---
compiler/rustc_mir_transform/src/copy_prop.rs | 1 +
1 file changed, 1 insertion(+)
diff --git a/compiler/rustc_mir_transform/src/copy_prop.rs b/compiler/rustc_mir_transform/src/copy_prop.rs
index 8f16df93a56d1..6e279232bcb48 100644
--- a/compiler/rustc_mir_transform/src/copy_prop.rs
+++ b/compiler/rustc_mir_transform/src/copy_prop.rs
@@ -153,6 +153,7 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'_, 'tcx> {
fn visit_operand(&mut self, operand: &mut Operand<'tcx>, loc: Location) {
if let Operand::Move(place) = *operand
+ // A move out of a projection of a copy is equivalent to a copy of the original projection.
&& !place.has_deref()
&& !self.fully_moved.contains(place.local)
{