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Implement checked Shl/Shr at MIR building.

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This commit is contained in:
Camille GILLOT 2023-02-13 21:08:15 +00:00
parent 43ee4d15bf
commit dd582bd7db
7 changed files with 109 additions and 107 deletions
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23
compiler/rustc_codegen_cranelift/src/num.rs
View file

@ -170,14 +170,6 @@ pub(crate) fn codegen_checked_int_binop<'tcx>(
in_lhs: CValue<'tcx>,
in_rhs: CValue<'tcx>,
) -> CValue<'tcx> {
if bin_op != BinOp::Shl && bin_op != BinOp::Shr {
assert_eq!(
in_lhs.layout().ty,
in_rhs.layout().ty,
"checked int binop requires lhs and rhs of same type"
);
}
let lhs = in_lhs.load_scalar(fx);
let rhs = in_rhs.load_scalar(fx);
@ -271,21 +263,6 @@ pub(crate) fn codegen_checked_int_binop<'tcx>(
_ => unreachable!("invalid non-integer type {}", ty),
}
}
BinOp::Shl => {
let val = fx.bcx.ins().ishl(lhs, rhs);
let ty = fx.bcx.func.dfg.value_type(val);
let max_shift = i64::from(ty.bits()) - 1;
let has_overflow = fx.bcx.ins().icmp_imm(IntCC::UnsignedGreaterThan, rhs, max_shift);
(val, has_overflow)
}
BinOp::Shr => {
let val =
if !signed { fx.bcx.ins().ushr(lhs, rhs) } else { fx.bcx.ins().sshr(lhs, rhs) };
let ty = fx.bcx.func.dfg.value_type(val);
let max_shift = i64::from(ty.bits()) - 1;
let has_overflow = fx.bcx.ins().icmp_imm(IntCC::UnsignedGreaterThan, rhs, max_shift);
(val, has_overflow)
}
_ => bug!("binop {:?} on checked int/uint lhs: {:?} rhs: {:?}", bin_op, in_lhs, in_rhs),
};

11
compiler/rustc_codegen_ssa/src/mir/rvalue.rs
View file

@ -663,17 +663,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
};
bx.checked_binop(oop, input_ty, lhs, rhs)
}
mir::BinOp::Shl | mir::BinOp::Shr => {
let lhs_llty = bx.cx().val_ty(lhs);
let rhs_llty = bx.cx().val_ty(rhs);
let invert_mask = common::shift_mask_val(bx, lhs_llty, rhs_llty, true);
let outer_bits = bx.and(rhs, invert_mask);
let of = bx.icmp(IntPredicate::IntNE, outer_bits, bx.cx().const_null(rhs_llty));
let val = self.codegen_scalar_binop(bx, op, lhs, rhs, input_ty);
(val, of)
}
_ => bug!("Operator `{:?}` is not a checkable operator", op),
};

9
compiler/rustc_const_eval/src/transform/validate.rs
View file

@ -553,15 +553,6 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
);
}
}
Shl | Shr => {
for x in [a, b] {
check_kinds!(
x,
"Cannot perform checked shift on non-integer type {:?}",
ty::Uint(..) | ty::Int(..)
)
}
}
_ => self.fail(location, format!("There is no checked version of {:?}", op)),
}
}

24
compiler/rustc_middle/src/ty/util.rs
View file

@ -59,22 +59,13 @@ impl<'tcx> fmt::Display for Discr<'tcx> {
}
}
fn int_size_and_signed<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> (Size, bool) {
let (int, signed) = match *ty.kind() {
ty::Int(ity) => (Integer::from_int_ty(&tcx, ity), true),
ty::Uint(uty) => (Integer::from_uint_ty(&tcx, uty), false),
_ => bug!("non integer discriminant"),
};
(int.size(), signed)
}
impl<'tcx> Discr<'tcx> {
/// Adds `1` to the value and wraps around if the maximum for the type is reached.
pub fn wrap_incr(self, tcx: TyCtxt<'tcx>) -> Self {
self.checked_add(tcx, 1).0
}
pub fn checked_add(self, tcx: TyCtxt<'tcx>, n: u128) -> (Self, bool) {
let (size, signed) = int_size_and_signed(tcx, self.ty);
let (size, signed) = self.ty.int_size_and_signed(tcx);
let (val, oflo) = if signed {
let min = size.signed_int_min();
let max = size.signed_int_max();
@ -922,12 +913,21 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for OpaqueTypeExpander<'tcx> {
}
impl<'tcx> Ty<'tcx> {
pub fn int_size_and_signed(self, tcx: TyCtxt<'tcx>) -> (Size, bool) {
let (int, signed) = match *self.kind() {
ty::Int(ity) => (Integer::from_int_ty(&tcx, ity), true),
ty::Uint(uty) => (Integer::from_uint_ty(&tcx, uty), false),
_ => bug!("non integer discriminant"),
};
(int.size(), signed)
}
/// Returns the maximum value for the given numeric type (including `char`s)
/// or returns `None` if the type is not numeric.
pub fn numeric_max_val(self, tcx: TyCtxt<'tcx>) -> Option<ty::Const<'tcx>> {
let val = match self.kind() {
ty::Int(_) | ty::Uint(_) => {
let (size, signed) = int_size_and_signed(tcx, self);
let (size, signed) = self.int_size_and_signed(tcx);
let val =
if signed { size.signed_int_max() as u128 } else { size.unsigned_int_max() };
Some(val)
@ -948,7 +948,7 @@ impl<'tcx> Ty<'tcx> {
pub fn numeric_min_val(self, tcx: TyCtxt<'tcx>) -> Option<ty::Const<'tcx>> {
let val = match self.kind() {
ty::Int(_) | ty::Uint(_) => {
let (size, signed) = int_size_and_signed(tcx, self);
let (size, signed) = self.int_size_and_signed(tcx);
let val = if signed { size.truncate(size.signed_int_min() as u128) } else { 0 };
Some(val)
}

85
compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
View file

@ -9,6 +9,7 @@ use crate::build::expr::category::{Category, RvalueFunc};
use crate::build::{BlockAnd, BlockAndExtension, Builder, NeedsTemporary};
use rustc_hir::lang_items::LangItem;
use rustc_middle::middle::region;
use rustc_middle::mir::interpret::Scalar;
use rustc_middle::mir::AssertKind;
use rustc_middle::mir::Place;
use rustc_middle::mir::*;
@ -519,30 +520,68 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
) -> BlockAnd<Rvalue<'tcx>> {
let source_info = self.source_info(span);
let bool_ty = self.tcx.types.bool;
if self.check_overflow && op.is_checkable() && ty.is_integral() {
let result_tup = self.tcx.mk_tup(&[ty, bool_ty]);
let result_value = self.temp(result_tup, span);
let rvalue = match op {
BinOp::Add | BinOp::Sub | BinOp::Mul if self.check_overflow && ty.is_integral() => {
let result_tup = self.tcx.mk_tup(&[ty, bool_ty]);
let result_value = self.temp(result_tup, span);
self.cfg.push_assign(
block,
source_info,
result_value,
Rvalue::CheckedBinaryOp(op, Box::new((lhs.to_copy(), rhs.to_copy()))),
);
let val_fld = Field::new(0);
let of_fld = Field::new(1);
self.cfg.push_assign(
block,
source_info,
result_value,
Rvalue::CheckedBinaryOp(op, Box::new((lhs.to_copy(), rhs.to_copy()))),
);
let val_fld = Field::new(0);
let of_fld = Field::new(1);
let tcx = self.tcx;
let val = tcx.mk_place_field(result_value, val_fld, ty);
let of = tcx.mk_place_field(result_value, of_fld, bool_ty);
let tcx = self.tcx;
let val = tcx.mk_place_field(result_value, val_fld, ty);
let of = tcx.mk_place_field(result_value, of_fld, bool_ty);
let err = AssertKind::Overflow(op, lhs, rhs);
let err = AssertKind::Overflow(op, lhs, rhs);
block = self.assert(block, Operand::Move(of), false, err, span);
block = self.assert(block, Operand::Move(of), false, err, span);
Rvalue::Use(Operand::Move(val))
}
BinOp::Shl | BinOp::Shr if self.check_overflow && ty.is_integral() => {
// Consider that the shift overflows if `rhs < 0` or `rhs >= bits`.
// This can be encoded as a single operation as `(rhs & -bits) != 0`.
let (size, _) = ty.int_size_and_signed(self.tcx);
let bits = size.bits();
debug_assert!(bits.is_power_of_two());
let mask = !((bits - 1) as u128);
block.and(Rvalue::Use(Operand::Move(val)))
} else {
if ty.is_integral() && (op == BinOp::Div || op == BinOp::Rem) {
let rhs_ty = rhs.ty(&self.local_decls, self.tcx);
let (rhs_size, _) = rhs_ty.int_size_and_signed(self.tcx);
let mask = Operand::const_from_scalar(
self.tcx,
rhs_ty,
Scalar::from_uint(rhs_size.truncate(mask), rhs_size),
span,
);
let outer_bits = self.temp(rhs_ty, span);
self.cfg.push_assign(
block,
source_info,
outer_bits,
Rvalue::BinaryOp(BinOp::BitAnd, Box::new((rhs.to_copy(), mask))),
);
let overflows = self.temp(bool_ty, span);
let zero = self.zero_literal(span, rhs_ty);
self.cfg.push_assign(
block,
source_info,
overflows,
Rvalue::BinaryOp(BinOp::Ne, Box::new((Operand::Move(outer_bits), zero))),
);
let overflow_err = AssertKind::Overflow(op, lhs.to_copy(), rhs.to_copy());
block = self.assert(block, Operand::Move(overflows), false, overflow_err, span);
Rvalue::BinaryOp(op, Box::new((lhs, rhs)))
}
BinOp::Div | BinOp::Rem if ty.is_integral() => {
// 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.
@ -601,10 +640,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
block = self.assert(block, Operand::Move(of), false, overflow_err, span);
}
}
block.and(Rvalue::BinaryOp(op, Box::new((lhs, rhs))))
}
Rvalue::BinaryOp(op, Box::new((lhs, rhs)))
}
_ => Rvalue::BinaryOp(op, Box::new((lhs, rhs))),
};
block.and(rvalue)
}
fn build_zero_repeat(