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as_rvalue.rs
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as_rvalue.rs
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// 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.
//! See docs in build/expr/mod.rs
use std;
use rustc_const_math::{ConstMathErr, Op};
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::indexed_vec::Idx;
use build::{BlockAnd, BlockAndExtension, Builder};
use build::expr::category::{Category, RvalueFunc};
use hair::*;
use rustc_const_math::{ConstInt, ConstIsize};
use rustc::middle::const_val::ConstVal;
use rustc::middle::region::CodeExtent;
use rustc::ty;
use rustc::mir::*;
use syntax::ast;
use syntax_pos::Span;
impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
/// See comment on `as_local_operand`
pub fn as_local_rvalue<M>(&mut self, block: BasicBlock, expr: M)
-> BlockAnd<Rvalue<'tcx>>
where M: Mirror<'tcx, Output = Expr<'tcx>>
{
let topmost_scope = self.topmost_scope(); // FIXME(#6393)
self.as_rvalue(block, Some(topmost_scope), expr)
}
/// Compile `expr`, yielding an rvalue.
pub fn as_rvalue<M>(&mut self, block: BasicBlock, scope: Option<CodeExtent>, expr: M)
-> BlockAnd<Rvalue<'tcx>>
where M: Mirror<'tcx, Output = Expr<'tcx>>
{
let expr = self.hir.mirror(expr);
self.expr_as_rvalue(block, scope, expr)
}
fn expr_as_rvalue(&mut self,
mut block: BasicBlock,
scope: Option<CodeExtent>,
expr: Expr<'tcx>)
-> BlockAnd<Rvalue<'tcx>> {
debug!("expr_as_rvalue(block={:?}, expr={:?})", block, expr);
let this = self;
let expr_span = expr.span;
let source_info = this.source_info(expr_span);
match expr.kind {
ExprKind::Scope { extent, value } => {
this.in_scope(extent, block, |this| this.as_rvalue(block, scope, value))
}
ExprKind::Repeat { value, count } => {
let value_operand = unpack!(block = this.as_operand(block, scope, value));
block.and(Rvalue::Repeat(value_operand, count))
}
ExprKind::Borrow { region, borrow_kind, arg } => {
let arg_lvalue = unpack!(block = this.as_lvalue(block, arg));
block.and(Rvalue::Ref(region, borrow_kind, arg_lvalue))
}
ExprKind::Binary { op, lhs, rhs } => {
let lhs = unpack!(block = this.as_operand(block, scope, lhs));
let rhs = unpack!(block = this.as_operand(block, scope, rhs));
this.build_binary_op(block, op, expr_span, expr.ty,
lhs, rhs)
}
ExprKind::Unary { op, arg } => {
let arg = unpack!(block = this.as_operand(block, scope, arg));
// Check for -MIN on signed integers
if this.hir.check_overflow() && op == UnOp::Neg && expr.ty.is_signed() {
let bool_ty = this.hir.bool_ty();
let minval = this.minval_literal(expr_span, expr.ty);
let is_min = this.temp(bool_ty);
this.cfg.push_assign(block, source_info, &is_min,
Rvalue::BinaryOp(BinOp::Eq, arg.clone(), minval));
let err = ConstMathErr::Overflow(Op::Neg);
block = this.assert(block, Operand::Consume(is_min), false,
AssertMessage::Math(err), expr_span);
}
block.and(Rvalue::UnaryOp(op, arg))
}
ExprKind::Box { value, value_extents } => {
let value = this.hir.mirror(value);
let result = this.temp(expr.ty);
// to start, malloc some memory of suitable type (thus far, uninitialized):
this.cfg.push_assign(block, source_info, &result, Rvalue::Box(value.ty));
this.in_scope(value_extents, block, |this| {
// schedule a shallow free of that memory, lest we unwind:
this.schedule_box_free(expr_span, value_extents, &result, value.ty);
// initialize the box contents:
unpack!(block = this.into(&result.clone().deref(), block, value));
block.and(Rvalue::Use(Operand::Consume(result)))
})
}
ExprKind::Cast { source } => {
let source = this.hir.mirror(source);
let source = unpack!(block = this.as_operand(block, scope, source));
block.and(Rvalue::Cast(CastKind::Misc, source, expr.ty))
}
ExprKind::Use { source } => {
let source = unpack!(block = this.as_operand(block, scope, source));
block.and(Rvalue::Use(source))
}
ExprKind::ReifyFnPointer { source } => {
let source = unpack!(block = this.as_operand(block, scope, source));
block.and(Rvalue::Cast(CastKind::ReifyFnPointer, source, expr.ty))
}
ExprKind::UnsafeFnPointer { source } => {
let source = unpack!(block = this.as_operand(block, scope, source));
block.and(Rvalue::Cast(CastKind::UnsafeFnPointer, source, expr.ty))
}
ExprKind::ClosureFnPointer { source } => {
let source = unpack!(block = this.as_operand(block, scope, source));
block.and(Rvalue::Cast(CastKind::ClosureFnPointer, source, expr.ty))
}
ExprKind::Unsize { source } => {
let source = unpack!(block = this.as_operand(block, scope, source));
block.and(Rvalue::Cast(CastKind::Unsize, source, expr.ty))
}
ExprKind::Array { fields } => {
// (*) We would (maybe) be closer to trans if we
// handled this and other aggregate cases via
// `into()`, not `as_rvalue` -- in that case, instead
// of generating
//
// let tmp1 = ...1;
// let tmp2 = ...2;
// dest = Rvalue::Aggregate(Foo, [tmp1, tmp2])
//
// we could just generate
//
// dest.f = ...1;
// dest.g = ...2;
//
// The problem is that then we would need to:
//
// (a) have a more complex mechanism for handling
// partial cleanup;
// (b) distinguish the case where the type `Foo` has a
// destructor, in which case creating an instance
// as a whole "arms" the destructor, and you can't
// write individual fields; and,
// (c) handle the case where the type Foo has no
// fields. We don't want `let x: ();` to compile
// to the same MIR as `let x = ();`.
// first process the set of fields
let el_ty = expr.ty.sequence_element_type(this.hir.tcx());
let fields: Vec<_> =
fields.into_iter()
.map(|f| unpack!(block = this.as_operand(block, scope, f)))
.collect();
block.and(Rvalue::Aggregate(AggregateKind::Array(el_ty), fields))
}
ExprKind::Tuple { fields } => { // see (*) above
// first process the set of fields
let fields: Vec<_> =
fields.into_iter()
.map(|f| unpack!(block = this.as_operand(block, scope, f)))
.collect();
block.and(Rvalue::Aggregate(AggregateKind::Tuple, fields))
}
ExprKind::Closure { closure_id, substs, upvars } => { // see (*) above
let upvars =
upvars.into_iter()
.map(|upvar| unpack!(block = this.as_operand(block, scope, upvar)))
.collect();
block.and(Rvalue::Aggregate(AggregateKind::Closure(closure_id, substs), upvars))
}
ExprKind::Adt {
adt_def, variant_index, substs, fields, base
} => { // see (*) above
let is_union = adt_def.is_union();
let active_field_index = if is_union { Some(fields[0].name.index()) } else { None };
// first process the set of fields that were provided
// (evaluating them in order given by user)
let fields_map: FxHashMap<_, _> = fields.into_iter()
.map(|f| (f.name, unpack!(block = this.as_operand(block, scope, f.expr))))
.collect();
let field_names = this.hir.all_fields(adt_def, variant_index);
let fields = if let Some(FruInfo { base, field_types }) = base {
let base = unpack!(block = this.as_lvalue(block, base));
// MIR does not natively support FRU, so for each
// base-supplied field, generate an operand that
// reads it from the base.
field_names.into_iter()
.zip(field_types.into_iter())
.map(|(n, ty)| match fields_map.get(&n) {
Some(v) => v.clone(),
None => Operand::Consume(base.clone().field(n, ty))
})
.collect()
} else {
field_names.iter().filter_map(|n| fields_map.get(n).cloned()).collect()
};
let adt = AggregateKind::Adt(adt_def, variant_index, substs, active_field_index);
block.and(Rvalue::Aggregate(adt, fields))
}
ExprKind::Assign { .. } |
ExprKind::AssignOp { .. } => {
block = unpack!(this.stmt_expr(block, expr));
block.and(this.unit_rvalue())
}
ExprKind::Literal { .. } |
ExprKind::Block { .. } |
ExprKind::Match { .. } |
ExprKind::If { .. } |
ExprKind::NeverToAny { .. } |
ExprKind::Loop { .. } |
ExprKind::LogicalOp { .. } |
ExprKind::Call { .. } |
ExprKind::Field { .. } |
ExprKind::Deref { .. } |
ExprKind::Index { .. } |
ExprKind::VarRef { .. } |
ExprKind::SelfRef |
ExprKind::Break { .. } |
ExprKind::Continue { .. } |
ExprKind::Return { .. } |
ExprKind::InlineAsm { .. } |
ExprKind::StaticRef { .. } => {
// these do not have corresponding `Rvalue` variants,
// so make an operand and then return that
debug_assert!(match Category::of(&expr.kind) {
Some(Category::Rvalue(RvalueFunc::AsRvalue)) => false,
_ => true,
});
let operand = unpack!(block = this.as_operand(block, scope, expr));
block.and(Rvalue::Use(operand))
}
}
}
pub fn build_binary_op(&mut self, mut block: BasicBlock,
op: BinOp, span: Span, ty: ty::Ty<'tcx>,
lhs: Operand<'tcx>, rhs: Operand<'tcx>) -> BlockAnd<Rvalue<'tcx>> {
let source_info = self.source_info(span);
let bool_ty = self.hir.bool_ty();
if self.hir.check_overflow() && op.is_checkable() && ty.is_integral() {
let result_tup = self.hir.tcx().intern_tup(&[ty, bool_ty], false);
let result_value = self.temp(result_tup);
self.cfg.push_assign(block, source_info,
&result_value, Rvalue::CheckedBinaryOp(op,
lhs,
rhs));
let val_fld = Field::new(0);
let of_fld = Field::new(1);
let val = result_value.clone().field(val_fld, ty);
let of = result_value.field(of_fld, bool_ty);
let err = ConstMathErr::Overflow(match op {
BinOp::Add => Op::Add,
BinOp::Sub => Op::Sub,
BinOp::Mul => Op::Mul,
BinOp::Shl => Op::Shl,
BinOp::Shr => Op::Shr,
_ => {
bug!("MIR build_binary_op: {:?} is not checkable", op)
}
});
block = self.assert(block, Operand::Consume(of), false,
AssertMessage::Math(err), span);
block.and(Rvalue::Use(Operand::Consume(val)))
} else {
if ty.is_integral() && (op == BinOp::Div || op == BinOp::Rem) {
// Checking division and remainder is more complex, since we 1. always check
// and 2. there are two possible failure cases, divide-by-zero and overflow.
let (zero_err, overflow_err) = if op == BinOp::Div {
(ConstMathErr::DivisionByZero,
ConstMathErr::Overflow(Op::Div))
} else {
(ConstMathErr::RemainderByZero,
ConstMathErr::Overflow(Op::Rem))
};
// Check for / 0
let is_zero = self.temp(bool_ty);
let zero = self.zero_literal(span, ty);
self.cfg.push_assign(block, source_info, &is_zero,
Rvalue::BinaryOp(BinOp::Eq, rhs.clone(), zero));
block = self.assert(block, Operand::Consume(is_zero), false,
AssertMessage::Math(zero_err), span);
// We only need to check for the overflow in one case:
// MIN / -1, and only for signed values.
if ty.is_signed() {
let neg_1 = self.neg_1_literal(span, ty);
let min = self.minval_literal(span, ty);
let is_neg_1 = self.temp(bool_ty);
let is_min = self.temp(bool_ty);
let of = self.temp(bool_ty);
// this does (rhs == -1) & (lhs == MIN). It could short-circuit instead
self.cfg.push_assign(block, source_info, &is_neg_1,
Rvalue::BinaryOp(BinOp::Eq, rhs.clone(), neg_1));
self.cfg.push_assign(block, source_info, &is_min,
Rvalue::BinaryOp(BinOp::Eq, lhs.clone(), min));
let is_neg_1 = Operand::Consume(is_neg_1);
let is_min = Operand::Consume(is_min);
self.cfg.push_assign(block, source_info, &of,
Rvalue::BinaryOp(BinOp::BitAnd, is_neg_1, is_min));
block = self.assert(block, Operand::Consume(of), false,
AssertMessage::Math(overflow_err), span);
}
}
block.and(Rvalue::BinaryOp(op, lhs, rhs))
}
}
// Helper to get a `-1` value of the appropriate type
fn neg_1_literal(&mut self, span: Span, ty: ty::Ty<'tcx>) -> Operand<'tcx> {
let literal = match ty.sty {
ty::TyInt(ity) => {
let val = match ity {
ast::IntTy::I8 => ConstInt::I8(-1),
ast::IntTy::I16 => ConstInt::I16(-1),
ast::IntTy::I32 => ConstInt::I32(-1),
ast::IntTy::I64 => ConstInt::I64(-1),
ast::IntTy::I128 => ConstInt::I128(-1),
ast::IntTy::Is => {
let int_ty = self.hir.tcx().sess.target.int_type;
let val = ConstIsize::new(-1, int_ty).unwrap();
ConstInt::Isize(val)
}
};
Literal::Value { value: ConstVal::Integral(val) }
}
_ => {
span_bug!(span, "Invalid type for neg_1_literal: `{:?}`", ty)
}
};
self.literal_operand(span, ty, literal)
}
// Helper to get the minimum value of the appropriate type
fn minval_literal(&mut self, span: Span, ty: ty::Ty<'tcx>) -> Operand<'tcx> {
let literal = match ty.sty {
ty::TyInt(ity) => {
let val = match ity {
ast::IntTy::I8 => ConstInt::I8(i8::min_value()),
ast::IntTy::I16 => ConstInt::I16(i16::min_value()),
ast::IntTy::I32 => ConstInt::I32(i32::min_value()),
ast::IntTy::I64 => ConstInt::I64(i64::min_value()),
ast::IntTy::I128 => ConstInt::I128(i128::min_value()),
ast::IntTy::Is => {
let int_ty = self.hir.tcx().sess.target.int_type;
let min = match int_ty {
ast::IntTy::I16 => std::i16::MIN as i64,
ast::IntTy::I32 => std::i32::MIN as i64,
ast::IntTy::I64 => std::i64::MIN,
_ => unreachable!()
};
let val = ConstIsize::new(min, int_ty).unwrap();
ConstInt::Isize(val)
}
};
Literal::Value { value: ConstVal::Integral(val) }
}
_ => {
span_bug!(span, "Invalid type for minval_literal: `{:?}`", ty)
}
};
self.literal_operand(span, ty, literal)
}
}