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// Copyright 2016 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.
use build::scope::BreakableScope;
use build::{BlockAnd, BlockAndExtension, BlockFrame, Builder};
use hair::*;
use rustc::mir::*;
impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
pub fn stmt_expr(&mut self, mut block: BasicBlock, expr: Expr<'tcx>) -> BlockAnd<()> {
let this = self;
let expr_span = expr.span;
let source_info = this.source_info(expr.span);
// Handle a number of expressions that don't need a destination at all. This
// avoids needing a mountain of temporary `()` variables.
let expr2 = expr.clone();
match expr.kind {
ExprKind::Scope {
region_scope,
lint_level,
value,
} => {
let value = this.hir.mirror(value);
this.in_scope((region_scope, source_info), lint_level, block, |this| {
this.stmt_expr(block, value)
})
}
ExprKind::Assign { lhs, rhs } => {
let lhs = this.hir.mirror(lhs);
let rhs = this.hir.mirror(rhs);
let lhs_span = lhs.span;
// Note: we evaluate assignments right-to-left. This
// is better for borrowck interaction with overloaded
// operators like x[j] = x[i].
debug!("stmt_expr Assign block_context.push(SubExpr) : {:?}", expr2);
this.block_context.push(BlockFrame::SubExpr);
// Generate better code for things that don't need to be
// dropped.
if this.hir.needs_drop(lhs.ty) {
let rhs = unpack!(block = this.as_local_operand(block, rhs));
let lhs = unpack!(block = this.as_place(block, lhs));
unpack!(block = this.build_drop_and_replace(block, lhs_span, lhs, rhs));
} else {
let rhs = unpack!(block = this.as_local_rvalue(block, rhs));
let lhs = unpack!(block = this.as_place(block, lhs));
this.cfg.push_assign(block, source_info, &lhs, rhs);
}
this.block_context.pop();
block.unit()
}
ExprKind::AssignOp { op, lhs, rhs } => {
// FIXME(#28160) there is an interesting semantics
// question raised here -- should we "freeze" the
// value of the lhs here? I'm inclined to think not,
// since it seems closer to the semantics of the
// overloaded version, which takes `&mut self`. This
// only affects weird things like `x += {x += 1; x}`
// -- is that equal to `x + (x + 1)` or `2*(x+1)`?
let lhs = this.hir.mirror(lhs);
let lhs_ty = lhs.ty;
debug!("stmt_expr AssignOp block_context.push(SubExpr) : {:?}", expr2);
this.block_context.push(BlockFrame::SubExpr);
// As above, RTL.
let rhs = unpack!(block = this.as_local_operand(block, rhs));
let lhs = unpack!(block = this.as_place(block, lhs));
// we don't have to drop prior contents or anything
// because AssignOp is only legal for Copy types
// (overloaded ops should be desugared into a call).
let result = unpack!(
block = this.build_binary_op(
block,
op,
expr_span,
lhs_ty,
Operand::Copy(lhs.clone()),
rhs
)
);
this.cfg.push_assign(block, source_info, &lhs, result);
this.block_context.pop();
block.unit()
}
ExprKind::Continue { label } => {
let BreakableScope {
continue_block,
region_scope,
..
} = *this.find_breakable_scope(expr_span, label);
let continue_block = continue_block
.expect("Attempted to continue in non-continuable breakable block");
this.exit_scope(
expr_span,
(region_scope, source_info),
block,
continue_block,
);
this.cfg.start_new_block().unit()
}
ExprKind::Break { label, value } => {
let (break_block, region_scope, destination) = {
let BreakableScope {
break_block,
region_scope,
ref break_destination,
..
} = *this.find_breakable_scope(expr_span, label);
(break_block, region_scope, break_destination.clone())
};
if let Some(value) = value {
debug!("stmt_expr Break val block_context.push(SubExpr) : {:?}", expr2);
this.block_context.push(BlockFrame::SubExpr);
unpack!(block = this.into(&destination, block, value));
this.block_context.pop();
} else {
this.cfg.push_assign_unit(block, source_info, &destination)
}
this.exit_scope(expr_span, (region_scope, source_info), block, break_block);
this.cfg.start_new_block().unit()
}
ExprKind::Return { value } => {
block = match value {
Some(value) => {
debug!("stmt_expr Return val block_context.push(SubExpr) : {:?}", expr2);
this.block_context.push(BlockFrame::SubExpr);
let result = unpack!(this.into(&Place::Local(RETURN_PLACE), block, value));
this.block_context.pop();
result
}
None => {
this.cfg
.push_assign_unit(block, source_info, &Place::Local(RETURN_PLACE));
block
}
};
let region_scope = this.region_scope_of_return_scope();
let return_block = this.return_block();
this.exit_scope(expr_span, (region_scope, source_info), block, return_block);
this.cfg.start_new_block().unit()
}
ExprKind::InlineAsm {
asm,
outputs,
inputs,
} => {
debug!("stmt_expr InlineAsm block_context.push(SubExpr) : {:?}", expr2);
this.block_context.push(BlockFrame::SubExpr);
let outputs = outputs
.into_iter()
.map(|output| unpack!(block = this.as_place(block, output)))
.collect::<Vec<_>>()
.into_boxed_slice();
let inputs = inputs
.into_iter()
.map(|input| unpack!(block = this.as_local_operand(block, input)))
.collect::<Vec<_>>()
.into_boxed_slice();
this.cfg.push(
block,
Statement {
source_info,
kind: StatementKind::InlineAsm {
asm: box asm.clone(),
outputs,
inputs,
},
},
);
this.block_context.pop();
block.unit()
}
_ => {
let expr_ty = expr.ty;
let temp = this.temp(expr.ty.clone(), expr_span);
unpack!(block = this.into(&temp, block, expr));
unpack!(block = this.build_drop(block, expr_span, temp, expr_ty));
block.unit()
}
}
}
}
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