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[const-prop] Extract some functions out of _const_prop
This commit is contained in:
Wesley Wiser
parent
e083273ec7
commit
397a2fd744
@ -469,6 +469,121 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
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}
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}
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fn check_unary_op(&mut self, arg: &Operand<'tcx>, source_info: SourceInfo) -> Option<()> {
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self.use_ecx(source_info, |this| {
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let ty = arg.ty(&this.local_decls, this.tcx);
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if ty.is_integral() {
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let arg = this.ecx.eval_operand(arg, None)?;
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let prim = this.ecx.read_immediate(arg)?;
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// Need to do overflow check here: For actual CTFE, MIR
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// generation emits code that does this before calling the op.
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if prim.to_bits()? == (1 << (prim.layout.size.bits() - 1)) {
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throw_panic!(OverflowNeg)
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}
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}
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Ok(())
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})?;
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Some(())
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}
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fn check_binary_op(
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&mut self,
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op: BinOp,
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left: &Operand<'tcx>,
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right: &Operand<'tcx>,
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source_info: SourceInfo,
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place_layout: TyLayout<'tcx>,
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overflow_check: bool,
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) -> Option<()> {
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let r = self.use_ecx(source_info, |this| {
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this.ecx.read_immediate(this.ecx.eval_operand(right, None)?)
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})?;
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if op == BinOp::Shr || op == BinOp::Shl {
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let left_bits = place_layout.size.bits();
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let right_size = r.layout.size;
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let r_bits = r.to_scalar().and_then(|r| r.to_bits(right_size));
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if r_bits.map_or(false, |b| b >= left_bits as u128) {
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let lint_root = self.lint_root(source_info)?;
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let dir = if op == BinOp::Shr { "right" } else { "left" };
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self.tcx.lint_hir(
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::rustc::lint::builtin::EXCEEDING_BITSHIFTS,
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lint_root,
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source_info.span,
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&format!("attempt to shift {} with overflow", dir),
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);
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return None;
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}
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}
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// If overflow checking is enabled (like in debug mode by default),
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// then we'll already catch overflow when we evaluate the `Assert` statement
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// in MIR. However, if overflow checking is disabled, then there won't be any
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// `Assert` statement and so we have to do additional checking here.
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if !overflow_check {
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self.use_ecx(source_info, |this| {
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let l = this.ecx.read_immediate(this.ecx.eval_operand(left, None)?)?;
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let (_, overflow, _ty) = this.ecx.overflowing_binary_op(op, l, r)?;
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if overflow {
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let err = err_panic!(Overflow(op)).into();
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return Err(err);
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}
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Ok(())
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})?;
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}
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Some(())
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}
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fn check_cast(
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&mut self,
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op: &Operand<'tcx>,
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ty: Ty<'tcx>,
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source_info: SourceInfo,
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place_layout: TyLayout<'tcx>,
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) -> Option<()> {
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if ty.is_integral() && op.ty(&self.local_decls, self.tcx).is_integral() {
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let value = self.use_ecx(source_info, |this| {
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this.ecx.read_immediate(this.ecx.eval_operand(op, None)?)
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})?;
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// Do not try to read bits for ZSTs
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if !value.layout.is_zst() {
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let value_size = value.layout.size;
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let value_bits = value.to_scalar().and_then(|r| r.to_bits(value_size));
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if let Ok(value_bits) = value_bits {
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let truncated = truncate(value_bits, place_layout.size);
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if truncated != value_bits {
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let scope = source_info.scope;
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let lint_root = match &self.source_scopes[scope].local_data {
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ClearCrossCrate::Set(data) => data.lint_root,
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ClearCrossCrate::Clear => return None,
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};
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self.tcx.lint_hir(
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::rustc::lint::builtin::CONST_ERR,
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lint_root,
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source_info.span,
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&format!(
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"truncating cast: the value {} requires {} bits but \
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the target type is only {} bits",
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value_bits,
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value_size.bits(),
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place_layout.size.bits()
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),
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);
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return None;
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}
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}
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}
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}
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Some(())
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}
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fn const_prop(
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&mut self,
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rvalue: &Rvalue<'tcx>,
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@ -476,8 +591,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
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source_info: SourceInfo,
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place: &Place<'tcx>,
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) -> Option<()> {
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let span = source_info.span;
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// #66397: Don't try to eval into large places as that can cause an OOM
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if place_layout.size >= Size::from_bytes(MAX_ALLOC_LIMIT) {
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return None;
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@ -498,66 +611,14 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
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// if an overflow would occur.
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Rvalue::UnaryOp(UnOp::Neg, arg) if !overflow_check => {
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trace!("checking UnaryOp(op = Neg, arg = {:?})", arg);
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self.use_ecx(source_info, |this| {
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let ty = arg.ty(&this.local_decls, this.tcx);
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if ty.is_integral() {
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let arg = this.ecx.eval_operand(arg, None)?;
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let prim = this.ecx.read_immediate(arg)?;
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// Need to do overflow check here: For actual CTFE, MIR
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// generation emits code that does this before calling the op.
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if prim.to_bits()? == (1 << (prim.layout.size.bits() - 1)) {
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throw_panic!(OverflowNeg)
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}
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}
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Ok(())
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})?;
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self.check_unary_op(arg, source_info)?;
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}
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// Additional checking: check for overflows on integer binary operations and report
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// them to the user as lints.
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Rvalue::BinaryOp(op, left, right) => {
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trace!("checking BinaryOp(op = {:?}, left = {:?}, right = {:?})", op, left, right);
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let r = self.use_ecx(source_info, |this| {
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this.ecx.read_immediate(this.ecx.eval_operand(right, None)?)
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})?;
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if *op == BinOp::Shr || *op == BinOp::Shl {
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let left_bits = place_layout.size.bits();
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let right_size = r.layout.size;
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let r_bits = r.to_scalar().and_then(|r| r.to_bits(right_size));
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if r_bits.map_or(false, |b| b >= left_bits as u128) {
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let lint_root = self.lint_root(source_info)?;
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let dir = if *op == BinOp::Shr { "right" } else { "left" };
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self.tcx.lint_hir(
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::rustc::lint::builtin::EXCEEDING_BITSHIFTS,
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lint_root,
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span,
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&format!("attempt to shift {} with overflow", dir),
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);
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return None;
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}
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}
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// If overflow checking is enabled (like in debug mode by default),
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// then we'll already catch overflow when we evaluate the `Assert` statement
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// in MIR. However, if overflow checking is disabled, then there won't be any
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// `Assert` statement and so we have to do additional checking here.
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if !overflow_check {
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self.use_ecx(source_info, |this| {
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let l = this.ecx.read_immediate(this.ecx.eval_operand(left, None)?)?;
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let (_, overflow, _ty) = this.ecx.overflowing_binary_op(*op, l, r)?;
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if overflow {
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let err = err_panic!(Overflow(*op)).into();
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return Err(err);
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}
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Ok(())
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})?;
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}
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self.check_binary_op(*op, left, right, source_info, place_layout, overflow_check)?;
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}
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// Work around: avoid ICE in miri. FIXME(wesleywiser)
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@ -586,41 +647,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
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Rvalue::Cast(CastKind::Misc, op, ty) => {
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trace!("checking Cast(Misc, {:?}, {:?})", op, ty);
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if ty.is_integral() && op.ty(&self.local_decls, self.tcx).is_integral() {
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let value = self.use_ecx(source_info, |this| {
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this.ecx.read_immediate(this.ecx.eval_operand(op, None)?)
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})?;
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// Do not try to read bits for ZSTs
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if !value.layout.is_zst() {
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let value_size = value.layout.size;
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let value_bits = value.to_scalar().and_then(|r| r.to_bits(value_size));
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if let Ok(value_bits) = value_bits {
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let truncated = truncate(value_bits, place_layout.size);
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if truncated != value_bits {
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let scope = source_info.scope;
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let lint_root = match &self.source_scopes[scope].local_data {
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ClearCrossCrate::Set(data) => data.lint_root,
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ClearCrossCrate::Clear => return None,
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};
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self.tcx.lint_hir(
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::rustc::lint::builtin::CONST_ERR,
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lint_root,
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span,
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&format!(
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"truncating cast: the value {} requires {} bits but \
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the target type is only {} bits",
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value_bits,
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value_size.bits(),
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place_layout.size.bits()
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),
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);
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return None;
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}
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}
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}
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}
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self.check_cast(op, ty, source_info, place_layout)?;
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}
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_ => {}
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