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Simplify MIR generation for logical ops
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sinkuu committed Dec 17, 2018
1 parent 1897657 commit e38e954
Showing 1 changed file with 23 additions and 30 deletions.
53 changes: 23 additions & 30 deletions src/librustc_mir/build/expr/into.rs
Original file line number Diff line number Diff line change
Expand Up @@ -126,66 +126,59 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
ExprKind::LogicalOp { op, lhs, rhs } => {
// And:
//
// [block: If(lhs)] -true-> [else_block: If(rhs)] -true-> [true_block]
// | | (false)
// +----------false-----------+------------------> [false_block]
// [block: If(lhs)] -true-> [else_block: dest = (rhs)]
// | (false)
// [shortcurcuit_block: dest = false]
//
// Or:
//
// [block: If(lhs)] -false-> [else_block: If(rhs)] -true-> [true_block]
// | (true) | (false)
// [true_block] [false_block]
// [block: If(lhs)] -false-> [else_block: dest = (rhs)]
// | (true)
// [shortcurcuit_block: dest = true]

let (true_block, false_block, mut else_block, join_block) = (
this.cfg.start_new_block(),
let (shortcircuit_block, mut else_block, join_block) = (
this.cfg.start_new_block(),
this.cfg.start_new_block(),
this.cfg.start_new_block(),
);

let lhs = unpack!(block = this.as_local_operand(block, lhs));
let blocks = match op {
LogicalOp::And => (else_block, false_block),
LogicalOp::Or => (true_block, else_block),
LogicalOp::And => (else_block, shortcircuit_block),
LogicalOp::Or => (shortcircuit_block, else_block),
};
let term = TerminatorKind::if_(this.hir.tcx(), lhs, blocks.0, blocks.1);
this.cfg.terminate(block, source_info, term);

let rhs = unpack!(else_block = this.as_local_operand(else_block, rhs));
let term = TerminatorKind::if_(this.hir.tcx(), rhs, true_block, false_block);
this.cfg.terminate(else_block, source_info, term);

this.cfg.push_assign_constant(
true_block,
shortcircuit_block,
source_info,
destination,
Constant {
span: expr_span,
ty: this.hir.bool_ty(),
user_ty: None,
literal: this.hir.true_literal(),
literal: match op {
LogicalOp::And => this.hir.false_literal(),
LogicalOp::Or => this.hir.true_literal(),
},
},
);

this.cfg.push_assign_constant(
false_block,
this.cfg.terminate(
shortcircuit_block,
source_info,
destination,
Constant {
span: expr_span,
ty: this.hir.bool_ty(),
user_ty: None,
literal: this.hir.false_literal(),
},
TerminatorKind::Goto { target: join_block },
);

this.cfg.terminate(
true_block,
let rhs = unpack!(else_block = this.as_local_operand(else_block, rhs));
this.cfg.push_assign(
else_block,
source_info,
TerminatorKind::Goto { target: join_block },
destination,
Rvalue::Use(rhs),
);
this.cfg.terminate(
false_block,
else_block,
source_info,
TerminatorKind::Goto { target: join_block },
);
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