Rollup merge of rust-lang#70891 - lcnr:replace-rvalue_aggregate, r=eddyb

unit rvalue, use constant `()` instead of tuple fixes rust-lang#70886 r? @eddyb

Author: Centril

src/librustc_mir/transform/promote_consts.rs

@@ -835,7 +835,11 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
  if self.keep_original {
  rhs.clone()
  } else {
- let unit = Rvalue::Aggregate(box AggregateKind::Tuple, vec![]);
+ let unit = Rvalue::Use(Operand::Constant(box Constant {
+ span: statement.source_info.span,
+ user_ty: None,
+ literal: ty::Const::zero_sized(self.tcx, self.tcx.types.unit),
+ }));
  mem::replace(rhs, unit)
  },
  statement.source_info,

src/librustc_mir_build/build/block.rs

@@ -187,7 +187,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
  if destination_ty.is_unit() {
  // We only want to assign an implicit `()` as the return value of the block if the
  // block does not diverge. (Otherwise, we may try to assign a unit to a `!`-type.)
- this.cfg.push_assign_unit(block, source_info, destination);
+ this.cfg.push_assign_unit(block, source_info, destination, this.hir.tcx());
  }
  }
  // Finally, we pop all the let scopes before exiting out from the scope of block

src/librustc_mir_build/build/cfg.rs

@@ -2,6 +2,7 @@
 
 use crate::build::CFG;
 use rustc_middle::mir::*;
+use rustc_middle::ty::{self, TyCtxt};
 
 impl<'tcx> CFG<'tcx> {
  crate fn block_data(&self, blk: BasicBlock) -> &BasicBlockData<'tcx> {
@@ -58,12 +59,17 @@ impl<'tcx> CFG<'tcx> {
  block: BasicBlock,
  source_info: SourceInfo,
  place: Place<'tcx>,
+ tcx: TyCtxt<'tcx>,
  ) {
  self.push_assign(
  block,
  source_info,
  place,
- Rvalue::Aggregate(box AggregateKind::Tuple, vec![]),
+ Rvalue::Use(Operand::Constant(box Constant {
+ span: source_info.span,
+ user_ty: None,
+ literal: ty::Const::zero_sized(tcx, tcx.types.unit),
+ })),
  );
  }
 

src/librustc_mir_build/build/expr/as_rvalue.rs

@@ -225,7 +225,11 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
  }
  ExprKind::Assign { .. } | ExprKind::AssignOp { .. } => {
  block = unpack!(this.stmt_expr(block, expr, None));
- block.and(this.unit_rvalue())
+ block.and(Rvalue::Use(Operand::Constant(box Constant {
+ span: expr_span,
+ user_ty: None,
+ literal: ty::Const::zero_sized(this.hir.tcx(), this.hir.tcx().types.unit),
+ })))
  }
  ExprKind::Yield { .. }
  | ExprKind::Literal { .. }

src/librustc_mir_build/build/expr/into.rs

@@ -331,7 +331,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
  | ExprKind::LlvmInlineAsm { .. }
  | ExprKind::Return { .. } => {
  unpack!(block = this.stmt_expr(block, expr, None));
- this.cfg.push_assign_unit(block, source_info, destination);
+ this.cfg.push_assign_unit(block, source_info, destination, this.hir.tcx());
  block.unit()
  }
 

src/librustc_mir_build/build/misc.rs

@@ -32,10 +32,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
  Operand::Constant(constant)
  }
 
- crate fn unit_rvalue(&mut self) -> Rvalue<'tcx> {
- Rvalue::Aggregate(box AggregateKind::Tuple, vec![])
- }
-
  // Returns a zero literal operand for the appropriate type, works for
  // bool, char and integers.
  crate fn zero_literal(&mut self, span: Span, ty: Ty<'tcx>) -> Operand<'tcx> {

src/librustc_mir_build/build/scope.rs

@@ -523,7 +523,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
  unpack!(block = self.into(destination, block, value));
  self.block_context.pop();
  } else {
- self.cfg.push_assign_unit(block, source_info, destination)
+ self.cfg.push_assign_unit(block, source_info, destination, self.hir.tcx())
  }
  } else {
  assert!(value.is_none(), "`return` and `break` should have a destination");

src/test/mir-opt/address-of/rustc.address_of_reborrow.SimplifyCfg-initial.after.mir

@@ -298,7 +298,13 @@ fn address_of_reborrow() -> () {
  StorageDead(_48); // bb0[157]: scope 13 at $DIR/address-of.rs:36:25: 36:26
  FakeRead(ForLet, _47); // bb0[158]: scope 13 at $DIR/address-of.rs:36:9: 36:10
  AscribeUserType(_47, o, UserTypeProjection { base: UserType(29), projs: [] }); // bb0[159]: scope 13 at $DIR/address-of.rs:36:12: 36:22
- _0 = (); // bb0[160]: scope 0 at $DIR/address-of.rs:3:26: 37:2
+ _0 = const (); // bb0[160]: scope 0 at $DIR/address-of.rs:3:26: 37:2
+ // ty::Const
+ // + ty: ()
+ // + val: Value(Scalar(<ZST>))
+ // mir::Constant
+ // + span: $DIR/address-of.rs:3:26: 37:2
+ // + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
  StorageDead(_47); // bb0[161]: scope 13 at $DIR/address-of.rs:37:1: 37:2
  StorageDead(_45); // bb0[162]: scope 12 at $DIR/address-of.rs:37:1: 37:2
  StorageDead(_44); // bb0[163]: scope 11 at $DIR/address-of.rs:37:1: 37:2

src/test/mir-opt/address-of/rustc.borrow_and_cast.SimplifyCfg-initial.after.mir

@@ -38,7 +38,13 @@ fn borrow_and_cast(_1: i32) -> () {
  _6 = &raw mut (*_7); // bb0[15]: scope 2 at $DIR/address-of.rs:44:13: 44:19
  FakeRead(ForLet, _6); // bb0[16]: scope 2 at $DIR/address-of.rs:44:9: 44:10
  StorageDead(_7); // bb0[17]: scope 2 at $DIR/address-of.rs:44:31: 44:32
- _0 = (); // bb0[18]: scope 0 at $DIR/address-of.rs:41:32: 45:2
+ _0 = const (); // bb0[18]: scope 0 at $DIR/address-of.rs:41:32: 45:2
+ // ty::Const
+ // + ty: ()
+ // + val: Value(Scalar(<ZST>))
+ // mir::Constant
+ // + span: $DIR/address-of.rs:41:32: 45:2
+ // + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
  StorageDead(_6); // bb0[19]: scope 2 at $DIR/address-of.rs:45:1: 45:2
  StorageDead(_4); // bb0[20]: scope 1 at $DIR/address-of.rs:45:1: 45:2
  StorageDead(_2); // bb0[21]: scope 0 at $DIR/address-of.rs:45:1: 45:2

src/test/mir-opt/array-index-is-temporary/32bit/rustc.main.SimplifyCfg-elaborate-drops.after.mir

@@ -82,7 +82,13 @@ fn main() -> () {
  _1[_7] = move _5; // bb2[0]: scope 3 at $DIR/array-index-is-temporary.rs:16:5: 16:29
  StorageDead(_5); // bb2[1]: scope 3 at $DIR/array-index-is-temporary.rs:16:28: 16:29
  StorageDead(_7); // bb2[2]: scope 3 at $DIR/array-index-is-temporary.rs:16:29: 16:30
- _0 = (); // bb2[3]: scope 0 at $DIR/array-index-is-temporary.rs:12:11: 17:2
+ _0 = const (); // bb2[3]: scope 0 at $DIR/array-index-is-temporary.rs:12:11: 17:2
+ // ty::Const
+ // + ty: ()
+ // + val: Value(Scalar(<ZST>))
+ // mir::Constant
+ // + span: $DIR/array-index-is-temporary.rs:12:11: 17:2
+ // + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
  StorageDead(_3); // bb2[4]: scope 2 at $DIR/array-index-is-temporary.rs:17:1: 17:2
  StorageDead(_2); // bb2[5]: scope 1 at $DIR/array-index-is-temporary.rs:17:1: 17:2
  StorageDead(_1); // bb2[6]: scope 0 at $DIR/array-index-is-temporary.rs:17:1: 17:2