Auto merge of rust-lang#47926 - mikhail-m1:subslice_pattern_array_dro…

…p2, r=nikomatsakis

add transform for uniform array move out

reworked second step for fix rust-lang#34708
previous try rust-lang#46686
r? @nikomatsakis

src/librustc_mir/transform/mod.rs

@@ -44,6 +44,7 @@ pub mod copy_prop;
 pub mod generator;
 pub mod inline;
 pub mod lower_128bit;
+pub mod uniform_array_move_out;
 
 pub(crate) fn provide(providers: &mut Providers) {
     self::qualify_consts::provide(providers);
@@ -197,6 +198,7 @@ fn mir_const<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> &'tcx Stea
         simplify::SimplifyCfg::new("initial"),
         type_check::TypeckMir,
         rustc_peek::SanityCheck,
+        uniform_array_move_out::UniformArrayMoveOut,
     ];
     tcx.alloc_steal_mir(mir)
 }
@@ -253,6 +255,7 @@ fn optimized_mir<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> &'tcx
 
         lower_128bit::Lower128Bit,
 
+
         // Optimizations begin.
         inline::Inline,
         instcombine::InstCombine,

src/librustc_mir/transform/uniform_array_move_out.rs

@@ -0,0 +1,153 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// This pass converts move out from array by Subslice and
+// ConstIndex{.., from_end: true} to ConstIndex move out(s) from begin
+// of array. It allows detect error by mir borrowck and elaborate
+// drops for array without additional work.
+//
+// Example:
+//
+// let a = [ box 1,box 2, box 3];
+// if b {
+//  let [_a.., _] = a;
+// } else {
+//  let [.., _b] = a;
+// }
+//
+//  mir statement _10 = move _2[:-1]; replaced by:
+//  StorageLive(_12);
+//  _12 = move _2[0 of 3];
+//  StorageLive(_13);
+//  _13 = move _2[1 of 3];
+//  _10 = [move _12, move _13]
+//  StorageDead(_12);
+//  StorageDead(_13);
+//
+//  and mir statement _11 = move _2[-1 of 1]; replaced by:
+//  _11 = move _2[2 of 3];
+//
+// FIXME: convert to Subslice back for performance reason
+// FIXME: integrate this transformation to the mir build
+
+use rustc::ty;
+use rustc::ty::TyCtxt;
+use rustc::mir::*;
+use rustc::mir::visit::Visitor;
+use transform::{MirPass, MirSource};
+use util::patch::MirPatch;
+
+pub struct UniformArrayMoveOut;
+
+impl MirPass for UniformArrayMoveOut {
+    fn run_pass<'a, 'tcx>(&self,
+                          tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                          _src: MirSource,
+                          mir: &mut Mir<'tcx>) {
+        let mut patch = MirPatch::new(mir);
+        {
+            let mut visitor = UniformArrayMoveOutVisitor{mir, patch: &mut patch, tcx};
+            visitor.visit_mir(mir);
+        }
+        patch.apply(mir);
+    }
+}
+
+struct UniformArrayMoveOutVisitor<'a, 'tcx: 'a> {
+    mir: &'a Mir<'tcx>,
+    patch: &'a mut MirPatch<'tcx>,
+    tcx: TyCtxt<'a, 'tcx, 'tcx>,
+}
+
+impl<'a, 'tcx> Visitor<'tcx> for UniformArrayMoveOutVisitor<'a, 'tcx> {
+    fn visit_statement(&mut self,
+                       block: BasicBlock,
+                       statement: &Statement<'tcx>,
+                       location: Location) {
+        if let StatementKind::Assign(ref dst_place,
+                                     Rvalue::Use(Operand::Move(ref src_place))) = statement.kind {
+            if let Place::Projection(ref proj) = *src_place {
+                if let ProjectionElem::ConstantIndex{offset: _,
+                                                     min_length: _,
+                                                     from_end: false} = proj.elem {
+                    // no need to transformation
+                } else {
+                    let place_ty = proj.base.ty(self.mir, self.tcx).to_ty(self.tcx);
+                    if let ty::TyArray(item_ty, const_size) = place_ty.sty {
+                        if let Some(size) = const_size.val.to_const_int().and_then(|v| v.to_u64()) {
+                            assert!(size <= (u32::max_value() as u64),
+                                    "unform array move out doesn't supported
+                                     for array bigger then u32");
+                            self.uniform(location, dst_place, proj, item_ty, size as u32);
+                        }
+                    }
+
+                }
+            }
+        }
+        return self.super_statement(block, statement, location);
+    }
+}
+
+impl<'a, 'tcx> UniformArrayMoveOutVisitor<'a, 'tcx> {
+    fn uniform(&mut self,
+               location: Location,
+               dst_place: &Place<'tcx>,
+               proj: &PlaceProjection<'tcx>,
+               item_ty: &'tcx ty::TyS<'tcx>,
+               size: u32) {
+        match proj.elem {
+            // uniform _10 = move _2[:-1];
+            ProjectionElem::Subslice{from, to} => {
+                self.patch.make_nop(location);
+                let temps : Vec<_> = (from..(size-to)).map(|i| {
+                    let temp = self.patch.new_temp(item_ty, self.mir.source_info(location).span);
+                    self.patch.add_statement(location, StatementKind::StorageLive(temp));
+                    self.patch.add_assign(location,
+                                          Place::Local(temp),
+                                          Rvalue::Use(
+                                              Operand::Move(
+                                                  Place::Projection(box PlaceProjection{
+                                                      base: proj.base.clone(),
+                                                      elem: ProjectionElem::ConstantIndex{
+                                                          offset: i,
+                                                          min_length: size,
+                                                          from_end: false}
+                                                  }))));
+                    temp
+                }).collect();
+                self.patch.add_assign(location,
+                                      dst_place.clone(),
+                                      Rvalue::Aggregate(box AggregateKind::Array(item_ty),
+                                      temps.iter().map(
+                                          |x| Operand::Move(Place::Local(*x))).collect()
+                                      ));
+                for temp in temps {
+                    self.patch.add_statement(location, StatementKind::StorageDead(temp));
+                }
+            }
+            // _11 = move _2[-1 of 1];
+            ProjectionElem::ConstantIndex{offset, min_length: _, from_end: true} => {
+                self.patch.make_nop(location);
+                self.patch.add_assign(location,
+                                      dst_place.clone(),
+                                      Rvalue::Use(
+                                          Operand::Move(
+                                              Place::Projection(box PlaceProjection{
+                                                  base: proj.base.clone(),
+                                                  elem: ProjectionElem::ConstantIndex{
+                                                      offset: size - offset,
+                                                      min_length: size,
+                                                      from_end: false }}))));
+            }
+            _ => {}
+        }
+    }
+}

src/librustc_mir/util/patch.rs

@@ -23,6 +23,7 @@ pub struct MirPatch<'tcx> {
     new_locals: Vec<LocalDecl<'tcx>>,
     resume_block: BasicBlock,
     next_local: usize,
+    make_nop: Vec<Location>,
 }
 
 impl<'tcx> MirPatch<'tcx> {
@@ -33,7 +34,8 @@ impl<'tcx> MirPatch<'tcx> {
             new_statements: vec![],
             new_locals: vec![],
             next_local: mir.local_decls.len(),
-            resume_block: START_BLOCK
+            resume_block: START_BLOCK,
+            make_nop: vec![]
         };
 
         // make sure the MIR we create has a resume block. It is
@@ -131,7 +133,15 @@ impl<'tcx> MirPatch<'tcx> {
         self.add_statement(loc, StatementKind::Assign(place, rv));
     }
 
+    pub fn make_nop(&mut self, loc: Location) {
+        self.make_nop.push(loc);
+    }
+
     pub fn apply(self, mir: &mut Mir<'tcx>) {
+        debug!("MirPatch: make nops at: {:?}", self.make_nop);
+        for loc in self.make_nop {
+            mir.make_statement_nop(loc);
+        }
         debug!("MirPatch: {:?} new temps, starting from index {}: {:?}",
                self.new_locals.len(), mir.local_decls.len(), self.new_locals);
         debug!("MirPatch: {} new blocks, starting from index {}",

src/test/compile-fail/borrowck/borrowck-move-out-from-array.rs

@@ -0,0 +1,30 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// revisions: ast mir
+//[mir]compile-flags: -Z borrowck=mir
+
+#![feature(box_syntax, slice_patterns, advanced_slice_patterns)]
+
+fn move_out_from_begin_and_end() {
+    let a = [box 1, box 2];
+    let [_, _x] = a;
+    let [.., _y] = a; //[ast]~ ERROR [E0382]
+                      //[mir]~^ ERROR [E0382]
+}
+
+fn move_out_by_const_index_and_subslice() {
+    let a = [box 1, box 2];
+    let [_x, _] = a;
+    let [_y..] = a; //[ast]~ ERROR [E0382]
+                    //[mir]~^ ERROR [E0382]
+}
+
+fn main() {}

src/test/mir-opt/uniform_array_move_out.rs

@@ -0,0 +1,59 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(box_syntax, slice_patterns, advanced_slice_patterns)]
+
+fn move_out_from_end() {
+    let a = [box 1, box 2];
+    let [.., _y] = a;
+}
+
+fn move_out_by_subslice() {
+    let a = [box 1, box 2];
+    let [_y..] = a;
+}
+
+fn main() {
+    move_out_by_subslice();
+    move_out_from_end();
+}
+
+// END RUST SOURCE
+
+// START rustc.move_out_from_end.UniformArrayMoveOut.before.mir
+//     StorageLive(_6);
+//      _6 = move _1[-1 of 1];
+//      _0 = ();
+// END rustc.move_out_from_end.UniformArrayMoveOut.before.mir
+
+// START rustc.move_out_from_end.UniformArrayMoveOut.after.mir
+//     StorageLive(_6);
+//      _6 = move _1[1 of 2];
+//      nop;
+//      _0 = ();
+// END rustc.move_out_from_end.UniformArrayMoveOut.after.mir
+
+// START rustc.move_out_by_subslice.UniformArrayMoveOut.before.mir
+//     StorageLive(_6);
+//      _6 = move _1[0:];
+// END rustc.move_out_by_subslice.UniformArrayMoveOut.before.mir
+
+// START rustc.move_out_by_subslice.UniformArrayMoveOut.after.mir
+//     StorageLive(_6);
+//     StorageLive(_7);
+//     _7 = move _1[0 of 2];
+//     StorageLive(_8);
+//     _8 = move _1[1 of 2];
+//     _6 = [move _7, move _8];
+//     StorageDead(_7);
+//     StorageDead(_8);
+//     nop;
+//     _0 = ();
+// END rustc.move_out_by_subslice.UniformArrayMoveOut.after.mir

src/test/run-pass/dynamic-drop.rs

@@ -225,6 +225,43 @@ fn slice_pattern_one_of(a: &Allocator, i: usize) {
     };
 }
 
+fn subslice_pattern_from_end(a: &Allocator, arg: bool) {
+    let a = [a.alloc(), a.alloc(), a.alloc()];
+    if arg {
+        let[.., _x, _] = a;
+    } else {
+        let[_, _y..] = a;
+    }
+}
+
+fn subslice_pattern_from_end_with_drop(a: &Allocator, arg: bool, arg2: bool) {
+    let a = [a.alloc(), a.alloc(), a.alloc(), a.alloc(), a.alloc()];
+    if arg2 {
+        drop(a);
+        return;
+    }
+
+    if arg {
+        let[.., _x, _] = a;
+    } else {
+        let[_, _y..] = a;
+    }
+}
+
+fn slice_pattern_reassign(a: &Allocator) {
+    let mut ar = [a.alloc(), a.alloc()];
+    let[_, _x] = ar;
+    ar = [a.alloc(), a.alloc()];
+    let[.., _y] = ar;
+}
+
+fn subslice_pattern_reassign(a: &Allocator) {
+    let mut ar = [a.alloc(), a.alloc(), a.alloc()];
+    let[_, _, _x] = ar;
+    ar = [a.alloc(), a.alloc(), a.alloc()];
+    let[_, _y..] = ar;
+}
+
 fn run_test<F>(mut f: F)
     where F: FnMut(&Allocator)
 {
@@ -303,5 +340,14 @@ fn main() {
     run_test(|a| slice_pattern_one_of(a, 2));
     run_test(|a| slice_pattern_one_of(a, 3));
 
+    run_test(|a| subslice_pattern_from_end(a, true));
+    run_test(|a| subslice_pattern_from_end(a, false));
+    run_test(|a| subslice_pattern_from_end_with_drop(a, true, true));
+    run_test(|a| subslice_pattern_from_end_with_drop(a, true, false));
+    run_test(|a| subslice_pattern_from_end_with_drop(a, false, true));
+    run_test(|a| subslice_pattern_from_end_with_drop(a, false, false));
+    run_test(|a| slice_pattern_reassign(a));
+    run_test(|a| subslice_pattern_reassign(a));
+
     run_test_nopanic(|a| union1(a));
 }