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Move Ref-from-arg checking from step.rs to const_prop.rs
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@wesleywiser
wesleywiser committed Sep 14, 2019
1 parent 039fc48 commit 0b333ef
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Showing 2 changed files with 95 additions and 99 deletions.
21 changes: 2 additions & 19 deletions src/librustc_mir/interpret/step.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,11 +2,11 @@
//!
//! The main entry point is the `step` method.
use rustc::mir::{self, Place, PlaceBase};
use rustc::mir;
use rustc::ty::layout::LayoutOf;
use rustc::mir::interpret::{InterpResult, Scalar, PointerArithmetic};

use super::{InterpCx, LocalValue, Machine};
use super::{InterpCx, Machine};

/// Classify whether an operator is "left-homogeneous", i.e., the LHS has the
/// same type as the result.
Expand Down Expand Up @@ -240,23 +240,6 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
}

Ref(_, _, ref place) => {
// FIXME(wesleywiser) we don't currently handle the case where we try to make a ref
// from a function argument that hasn't been assigned to in this function. So just
// report those as uninitialized for now.
if let Place {
base: PlaceBase::Local(local),
projection: None
} = place {
let alive =
if let LocalValue::Live(_) = self.frame().locals[*local].value {
true
} else { false };

if local.as_usize() <= self.frame().body.arg_count && !alive {
trace!("skipping Ref({:?})", place);
throw_unsup!(UninitializedLocal);
}
}
let src = self.eval_place(place)?;
let place = self.force_allocation(src)?;
if place.layout.size.bytes() > 0 {
Expand Down
173 changes: 93 additions & 80 deletions src/librustc_mir/transform/const_prop.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,7 @@ use rustc::ty::layout::{

use crate::interpret::{
self, InterpCx, ScalarMaybeUndef, Immediate, OpTy,
ImmTy, StackPopCleanup, LocalValue, LocalState,
StackPopCleanup, LocalValue, LocalState,
};
use crate::const_eval::{
CompileTimeInterpreter, error_to_const_error, mk_eval_cx,
Expand Down Expand Up @@ -311,102 +311,115 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
place: &Place<'tcx>,
) -> Option<Const<'tcx>> {
let span = source_info.span;
match *rvalue {

// if this isn't a supported operation, then return None
match rvalue {
Rvalue::Repeat(..) |
Rvalue::Aggregate(..) |
Rvalue::NullaryOp(NullOp::Box, _) |
Rvalue::Discriminant(..) => None,
Rvalue::Discriminant(..) => return None,

Rvalue::Use(_) |
Rvalue::Len(_) |
Rvalue::Cast(..) |
Rvalue::NullaryOp(..) |
Rvalue::CheckedBinaryOp(..) |
Rvalue::Ref(..) => {
self.use_ecx(source_info, |this| {
this.ecx.eval_rvalue_into_place(rvalue, place)?;
this.ecx.eval_place_to_op(place, Some(place_layout))
})
},
Rvalue::Ref(..) |
Rvalue::UnaryOp(..) |
Rvalue::BinaryOp(..) => { }
}

Rvalue::UnaryOp(op, ref arg) => {
let overflow_check = self.tcx.sess.overflow_checks();

self.use_ecx(source_info, |this| {
// We check overflow in debug mode already
// so should only check in release mode.
if op == UnOp::Neg && !overflow_check {
let ty = arg.ty(&this.local_decls, this.tcx);

if ty.is_integral() {
let arg = this.ecx.eval_operand(arg, None)?;
let prim = this.ecx.read_immediate(arg)?;
// Need to do overflow check here: For actual CTFE, MIR
// generation emits code that does this before calling the op.
if prim.to_bits()? == (1 << (prim.layout.size.bits() - 1)) {
throw_panic!(OverflowNeg)
}
// perform any special checking for specific Rvalue types
if let Rvalue::UnaryOp(op, arg) = rvalue {
trace!("checking UnaryOp(op = {:?}, arg = {:?})", op, arg);
let overflow_check = self.tcx.sess.overflow_checks();

self.use_ecx(source_info, |this| {
// We check overflow in debug mode already
// so should only check in release mode.
if *op == UnOp::Neg && !overflow_check {
let ty = arg.ty(&this.local_decls, this.tcx);

if ty.is_integral() {
let arg = this.ecx.eval_operand(arg, None)?;
let prim = this.ecx.read_immediate(arg)?;
// Need to do overflow check here: For actual CTFE, MIR
// generation emits code that does this before calling the op.
if prim.to_bits()? == (1 << (prim.layout.size.bits() - 1)) {
throw_panic!(OverflowNeg)
}
}

this.ecx.eval_rvalue_into_place(rvalue, place)?;
this.ecx.eval_place_to_op(place, Some(place_layout))
})
}
Rvalue::BinaryOp(op, ref left, ref right) => {
trace!("rvalue binop {:?} for {:?} and {:?}", op, left, right);

let r = self.use_ecx(source_info, |this| {
this.ecx.read_immediate(this.ecx.eval_operand(right, None)?)
})?;
if op == BinOp::Shr || op == BinOp::Shl {
let left_bits = place_layout.size.bits();
let right_size = r.layout.size;
let r_bits = r.to_scalar().and_then(|r| r.to_bits(right_size));
if r_bits.ok().map_or(false, |b| b >= left_bits as u128) {
let source_scope_local_data = match self.source_scope_local_data {
ClearCrossCrate::Set(ref data) => data,
ClearCrossCrate::Clear => return None,
};
let dir = if op == BinOp::Shr {
"right"
} else {
"left"
};
let hir_id = source_scope_local_data[source_info.scope].lint_root;
self.tcx.lint_hir(
::rustc::lint::builtin::EXCEEDING_BITSHIFTS,
hir_id,
span,
&format!("attempt to shift {} with overflow", dir));
return None;
}
}
trace!("const evaluating {:?} for {:?} and {:?}", op, left, right);
let val = self.use_ecx(source_info, |this| {
let l = this.ecx.read_immediate(this.ecx.eval_operand(left, None)?)?;
let (val, overflow, _ty) = this.ecx.overflowing_binary_op(op, l, r)?;

// We check overflow in debug mode already
// so should only check in release mode.
if !this.tcx.sess.overflow_checks() && overflow {
let err = err_panic!(Overflow(op)).into();
return Err(err);
}

let val = ImmTy {
imm: Immediate::Scalar(val.into()),
layout: place_layout,
Ok(())
})?;
} else if let Rvalue::BinaryOp(op, left, right) = rvalue {
trace!("checking BinaryOp(op = {:?}, left = {:?}, right = {:?})", op, left, right);

let r = self.use_ecx(source_info, |this| {
this.ecx.read_immediate(this.ecx.eval_operand(right, None)?)
})?;
if *op == BinOp::Shr || *op == BinOp::Shl {
let left_bits = place_layout.size.bits();
let right_size = r.layout.size;
let r_bits = r.to_scalar().and_then(|r| r.to_bits(right_size));
if r_bits.ok().map_or(false, |b| b >= left_bits as u128) {
let source_scope_local_data = match self.source_scope_local_data {
ClearCrossCrate::Set(ref data) => data,
ClearCrossCrate::Clear => return None,
};
let dir = if *op == BinOp::Shr {
"right"
} else {
"left"
};
let hir_id = source_scope_local_data[source_info.scope].lint_root;
self.tcx.lint_hir(
::rustc::lint::builtin::EXCEEDING_BITSHIFTS,
hir_id,
span,
&format!("attempt to shift {} with overflow", dir));
return None;
}
}
self.use_ecx(source_info, |this| {
let l = this.ecx.read_immediate(this.ecx.eval_operand(left, None)?)?;
let (_, overflow, _ty) = this.ecx.overflowing_binary_op(*op, l, r)?;

// We check overflow in debug mode already
// so should only check in release mode.
if !this.tcx.sess.overflow_checks() && overflow {
let err = err_panic!(Overflow(*op)).into();
return Err(err);
}

let dest = this.ecx.eval_place(place)?;
this.ecx.write_immediate(*val, dest)?;

Ok(val)
})?;
Some(val.into())
},
Ok(())
})?;
} else if let Rvalue::Ref(_, _, place) = rvalue {
trace!("checking Ref({:?})", place);
// FIXME(wesleywiser) we don't currently handle the case where we try to make a ref
// from a function argument that hasn't been assigned to in this function.
if let Place {
base: PlaceBase::Local(local),
projection: box []
} = place {
let alive =
if let LocalValue::Live(_) = self.ecx.frame().locals[*local].value {
true
} else { false };

if local.as_usize() <= self.ecx.frame().body.arg_count && !alive {
trace!("skipping Ref({:?})", place);
return None;
}
}
}

self.use_ecx(source_info, |this| {
trace!("calling eval_rvalue_into_place(rvalue = {:?}, place = {:?})", rvalue, place);
this.ecx.eval_rvalue_into_place(rvalue, place)?;
this.ecx.eval_place_to_op(place, Some(place_layout))
})
}

fn operand_from_scalar(&self, scalar: Scalar, ty: Ty<'tcx>, span: Span) -> Operand<'tcx> {
Expand Down

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