blob: 44832df824064a769d063eb897a2a1efc7a63c12 [file] [log] [blame]
use rustc::hir;
use rustc::middle::const_val::{ConstEvalErr, ErrKind};
use rustc::middle::const_val::ErrKind::{TypeckError, CheckMatchError};
use rustc::mir;
use rustc::ty::{self, TyCtxt, Ty, Instance};
use rustc::ty::layout::{self, LayoutOf, Primitive};
use rustc::ty::subst::Subst;
use syntax::ast::Mutability;
use syntax::codemap::Span;
use syntax::codemap::DUMMY_SP;
use rustc::mir::interpret::{
EvalResult, EvalError, EvalErrorKind, GlobalId,
Value, Scalar, AllocId, Allocation, ConstValue,
};
use super::{Place, EvalContext, StackPopCleanup, ValTy, PlaceExtra, Memory, MemoryKind};
use std::fmt;
use std::error::Error;
use rustc_data_structures::sync::Lrc;
pub fn mk_borrowck_eval_cx<'a, 'mir, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
instance: Instance<'tcx>,
mir: &'mir mir::Mir<'tcx>,
span: Span,
) -> EvalResult<'tcx, EvalContext<'a, 'mir, 'tcx, CompileTimeEvaluator>> {
debug!("mk_borrowck_eval_cx: {:?}", instance);
let param_env = tcx.param_env(instance.def_id());
let mut ecx = EvalContext::new(tcx.at(span), param_env, CompileTimeEvaluator, ());
// insert a stack frame so any queries have the correct substs
ecx.push_stack_frame(
instance,
span,
mir,
Place::undef(),
StackPopCleanup::None,
)?;
Ok(ecx)
}
pub fn mk_eval_cx<'a, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
instance: Instance<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> EvalResult<'tcx, EvalContext<'a, 'tcx, 'tcx, CompileTimeEvaluator>> {
debug!("mk_eval_cx: {:?}, {:?}", instance, param_env);
let span = tcx.def_span(instance.def_id());
let mut ecx = EvalContext::new(tcx.at(span), param_env, CompileTimeEvaluator, ());
let mir = ecx.load_mir(instance.def)?;
// insert a stack frame so any queries have the correct substs
ecx.push_stack_frame(
instance,
mir.span,
mir,
Place::undef(),
StackPopCleanup::None,
)?;
Ok(ecx)
}
pub fn eval_promoted<'a, 'mir, 'tcx>(
ecx: &mut EvalContext<'a, 'mir, 'tcx, CompileTimeEvaluator>,
cid: GlobalId<'tcx>,
mir: &'mir mir::Mir<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> Option<(Value, Scalar, Ty<'tcx>)> {
ecx.with_fresh_body(|ecx| {
let res = eval_body_using_ecx(ecx, cid, Some(mir), param_env);
match res {
Ok(val) => Some(val),
Err(mut err) => {
ecx.report(&mut err, false, None);
None
}
}
})
}
pub fn eval_body<'a, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
cid: GlobalId<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> Option<(Value, Scalar, Ty<'tcx>)> {
let (res, ecx) = eval_body_and_ecx(tcx, cid, None, param_env);
match res {
Ok(val) => Some(val),
Err(mut err) => {
ecx.report(&mut err, true, None);
None
}
}
}
pub fn value_to_const_value<'tcx>(
ecx: &EvalContext<'_, '_, 'tcx, CompileTimeEvaluator>,
val: Value,
ty: Ty<'tcx>,
) -> &'tcx ty::Const<'tcx> {
let layout = ecx.tcx.layout_of(ty::ParamEnv::reveal_all().and(ty)).unwrap();
match (val, &layout.abi) {
(Value::Scalar(Scalar::Bits { defined: 0, ..}), _) if layout.is_zst() => {},
(Value::ByRef(..), _) |
(Value::Scalar(_), &layout::Abi::Scalar(_)) |
(Value::ScalarPair(..), &layout::Abi::ScalarPair(..)) => {},
_ => bug!("bad value/layout combo: {:#?}, {:#?}", val, layout),
}
let val = (|| {
match val {
Value::Scalar(val) => Ok(ConstValue::Scalar(val)),
Value::ScalarPair(a, b) => Ok(ConstValue::ScalarPair(a, b)),
Value::ByRef(ptr, align) => {
let ptr = ptr.to_ptr().unwrap();
let alloc = ecx.memory.get(ptr.alloc_id)?;
assert!(alloc.align.abi() >= align.abi());
assert!(alloc.bytes.len() as u64 - ptr.offset.bytes() >= layout.size.bytes());
let mut alloc = alloc.clone();
alloc.align = align;
let alloc = ecx.tcx.intern_const_alloc(alloc);
Ok(ConstValue::ByRef(alloc, ptr.offset))
}
}
})();
match val {
Ok(val) => ty::Const::from_const_value(ecx.tcx.tcx, val, ty),
Err(mut err) => {
ecx.report(&mut err, true, None);
bug!("miri error occured when converting Value to ConstValue")
}
}
}
fn eval_body_and_ecx<'a, 'mir, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
cid: GlobalId<'tcx>,
mir: Option<&'mir mir::Mir<'tcx>>,
param_env: ty::ParamEnv<'tcx>,
) -> (EvalResult<'tcx, (Value, Scalar, Ty<'tcx>)>, EvalContext<'a, 'mir, 'tcx, CompileTimeEvaluator>) {
debug!("eval_body_and_ecx: {:?}, {:?}", cid, param_env);
// we start out with the best span we have
// and try improving it down the road when more information is available
let span = tcx.def_span(cid.instance.def_id());
let span = mir.map(|mir| mir.span).unwrap_or(span);
let mut ecx = EvalContext::new(tcx.at(span), param_env, CompileTimeEvaluator, ());
let r = eval_body_using_ecx(&mut ecx, cid, mir, param_env);
(r, ecx)
}
fn eval_body_using_ecx<'a, 'mir, 'tcx>(
ecx: &mut EvalContext<'a, 'mir, 'tcx, CompileTimeEvaluator>,
cid: GlobalId<'tcx>,
mir: Option<&'mir mir::Mir<'tcx>>,
param_env: ty::ParamEnv<'tcx>,
) -> EvalResult<'tcx, (Value, Scalar, Ty<'tcx>)> {
debug!("eval_body: {:?}, {:?}", cid, param_env);
let tcx = ecx.tcx.tcx;
let mut mir = match mir {
Some(mir) => mir,
None => ecx.load_mir(cid.instance.def)?,
};
if let Some(index) = cid.promoted {
mir = &mir.promoted[index];
}
let layout = ecx.layout_of(mir.return_ty().subst(tcx, cid.instance.substs))?;
assert!(!layout.is_unsized());
let ptr = ecx.memory.allocate(
layout.size,
layout.align,
None,
)?;
let internally_mutable = !layout.ty.is_freeze(tcx, param_env, mir.span);
let is_static = tcx.is_static(cid.instance.def_id());
let mutability = if is_static == Some(hir::Mutability::MutMutable) || internally_mutable {
Mutability::Mutable
} else {
Mutability::Immutable
};
let cleanup = StackPopCleanup::MarkStatic(mutability);
let name = ty::tls::with(|tcx| tcx.item_path_str(cid.instance.def_id()));
let prom = cid.promoted.map_or(String::new(), |p| format!("::promoted[{:?}]", p));
trace!("const_eval: pushing stack frame for global: {}{}", name, prom);
assert!(mir.arg_count == 0);
ecx.push_stack_frame(
cid.instance,
mir.span,
mir,
Place::from_ptr(ptr, layout.align),
cleanup,
)?;
while ecx.step()? {}
let ptr = ptr.into();
// always try to read the value and report errors
let value = match ecx.try_read_value(ptr, layout.align, layout.ty)? {
Some(val) if is_static.is_none() => val,
// point at the allocation
_ => Value::ByRef(ptr, layout.align),
};
Ok((value, ptr, layout.ty))
}
pub struct CompileTimeEvaluator;
impl<'tcx> Into<EvalError<'tcx>> for ConstEvalError {
fn into(self) -> EvalError<'tcx> {
EvalErrorKind::MachineError(self.to_string()).into()
}
}
#[derive(Clone, Debug)]
enum ConstEvalError {
NeedsRfc(String),
NotConst(String),
}
impl fmt::Display for ConstEvalError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
use self::ConstEvalError::*;
match *self {
NeedsRfc(ref msg) => {
write!(
f,
"\"{}\" needs an rfc before being allowed inside constants",
msg
)
}
NotConst(ref msg) => write!(f, "{}", msg),
}
}
}
impl Error for ConstEvalError {
fn description(&self) -> &str {
use self::ConstEvalError::*;
match *self {
NeedsRfc(_) => "this feature needs an rfc before being allowed inside constants",
NotConst(_) => "this feature is not compatible with constant evaluation",
}
}
fn cause(&self) -> Option<&dyn Error> {
None
}
}
impl<'mir, 'tcx> super::Machine<'mir, 'tcx> for CompileTimeEvaluator {
type MemoryData = ();
type MemoryKinds = !;
fn eval_fn_call<'a>(
ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
instance: ty::Instance<'tcx>,
destination: Option<(Place, mir::BasicBlock)>,
args: &[ValTy<'tcx>],
span: Span,
sig: ty::FnSig<'tcx>,
) -> EvalResult<'tcx, bool> {
debug!("eval_fn_call: {:?}", instance);
if !ecx.tcx.is_const_fn(instance.def_id()) {
let def_id = instance.def_id();
let (op, oflo) = if let Some(op) = ecx.tcx.is_binop_lang_item(def_id) {
op
} else {
return Err(
ConstEvalError::NotConst(format!("calling non-const fn `{}`", instance)).into(),
);
};
let (dest, bb) = destination.expect("128 lowerings can't diverge");
let dest_ty = sig.output();
if oflo {
ecx.intrinsic_with_overflow(op, args[0], args[1], dest, dest_ty)?;
} else {
ecx.intrinsic_overflowing(op, args[0], args[1], dest, dest_ty)?;
}
ecx.goto_block(bb);
return Ok(true);
}
let mir = match ecx.load_mir(instance.def) {
Ok(mir) => mir,
Err(err) => {
if let EvalErrorKind::NoMirFor(ref path) = err.kind {
return Err(
ConstEvalError::NeedsRfc(format!("calling extern function `{}`", path))
.into(),
);
}
return Err(err);
}
};
let (return_place, return_to_block) = match destination {
Some((place, block)) => (place, StackPopCleanup::Goto(block)),
None => (Place::undef(), StackPopCleanup::None),
};
ecx.push_stack_frame(
instance,
span,
mir,
return_place,
return_to_block,
)?;
Ok(false)
}
fn call_intrinsic<'a>(
ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
instance: ty::Instance<'tcx>,
args: &[ValTy<'tcx>],
dest: Place,
dest_layout: layout::TyLayout<'tcx>,
target: mir::BasicBlock,
) -> EvalResult<'tcx> {
let substs = instance.substs;
let intrinsic_name = &ecx.tcx.item_name(instance.def_id()).as_str()[..];
match intrinsic_name {
"min_align_of" => {
let elem_ty = substs.type_at(0);
let elem_align = ecx.layout_of(elem_ty)?.align.abi();
let align_val = Scalar::Bits {
bits: elem_align as u128,
defined: dest_layout.size.bits() as u8,
};
ecx.write_scalar(dest, align_val, dest_layout.ty)?;
}
"size_of" => {
let ty = substs.type_at(0);
let size = ecx.layout_of(ty)?.size.bytes() as u128;
let size_val = Scalar::Bits {
bits: size,
defined: dest_layout.size.bits() as u8,
};
ecx.write_scalar(dest, size_val, dest_layout.ty)?;
}
"type_id" => {
let ty = substs.type_at(0);
let type_id = ecx.tcx.type_id_hash(ty) as u128;
let id_val = Scalar::Bits {
bits: type_id,
defined: dest_layout.size.bits() as u8,
};
ecx.write_scalar(dest, id_val, dest_layout.ty)?;
}
"ctpop" | "cttz" | "cttz_nonzero" | "ctlz" | "ctlz_nonzero" | "bswap" => {
let ty = substs.type_at(0);
let layout_of = ecx.layout_of(ty)?;
let bits = ecx.value_to_scalar(args[0])?.to_bits(layout_of.size)?;
let kind = match layout_of.abi {
ty::layout::Abi::Scalar(ref scalar) => scalar.value,
_ => Err(::rustc::mir::interpret::EvalErrorKind::TypeNotPrimitive(ty))?,
};
let out_val = if intrinsic_name.ends_with("_nonzero") {
if bits == 0 {
return err!(Intrinsic(format!("{} called on 0", intrinsic_name)));
}
numeric_intrinsic(intrinsic_name.trim_right_matches("_nonzero"), bits, kind)?
} else {
numeric_intrinsic(intrinsic_name, bits, kind)?
};
ecx.write_scalar(dest, out_val, ty)?;
}
name => return Err(
ConstEvalError::NeedsRfc(format!("calling intrinsic `{}`", name)).into()
),
}
ecx.goto_block(target);
// Since we pushed no stack frame, the main loop will act
// as if the call just completed and it's returning to the
// current frame.
Ok(())
}
fn try_ptr_op<'a>(
_ecx: &EvalContext<'a, 'mir, 'tcx, Self>,
_bin_op: mir::BinOp,
left: Scalar,
_left_ty: Ty<'tcx>,
right: Scalar,
_right_ty: Ty<'tcx>,
) -> EvalResult<'tcx, Option<(Scalar, bool)>> {
if left.is_bits() && right.is_bits() {
Ok(None)
} else {
Err(
ConstEvalError::NeedsRfc("Pointer arithmetic or comparison".to_string()).into(),
)
}
}
fn mark_static_initialized<'a>(
_mem: &mut Memory<'a, 'mir, 'tcx, Self>,
_id: AllocId,
_mutability: Mutability,
) -> EvalResult<'tcx, bool> {
Ok(false)
}
fn init_static<'a>(
ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
cid: GlobalId<'tcx>,
) -> EvalResult<'tcx, AllocId> {
Ok(ecx
.tcx
.alloc_map
.lock()
.intern_static(cid.instance.def_id()))
}
fn box_alloc<'a>(
_ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
_ty: Ty<'tcx>,
_dest: Place,
) -> EvalResult<'tcx> {
Err(
ConstEvalError::NeedsRfc("Heap allocations via `box` keyword".to_string()).into(),
)
}
fn global_item_with_linkage<'a>(
_ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
_instance: ty::Instance<'tcx>,
_mutability: Mutability,
) -> EvalResult<'tcx> {
Err(
ConstEvalError::NotConst("statics with `linkage` attribute".to_string()).into(),
)
}
}
pub fn const_val_field<'a, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
param_env: ty::ParamEnv<'tcx>,
instance: ty::Instance<'tcx>,
variant: Option<usize>,
field: mir::Field,
value: ConstValue<'tcx>,
ty: Ty<'tcx>,
) -> ::rustc::middle::const_val::EvalResult<'tcx> {
trace!("const_val_field: {:?}, {:?}, {:?}, {:?}", instance, field, value, ty);
let mut ecx = mk_eval_cx(tcx, instance, param_env).unwrap();
let result = (|| {
let value = ecx.const_value_to_value(value, ty)?;
let layout = ecx.layout_of(ty)?;
let (ptr, align) = match value {
Value::ByRef(ptr, align) => (ptr, align),
Value::ScalarPair(..) | Value::Scalar(_) => {
let ptr = ecx.alloc_ptr(ty)?.into();
ecx.write_value_to_ptr(value, ptr, layout.align, ty)?;
(ptr, layout.align)
},
};
let place = Place::Ptr {
ptr,
align,
extra: variant.map_or(PlaceExtra::None, PlaceExtra::DowncastVariant),
};
let (place, layout) = ecx.place_field(place, field, layout)?;
let (ptr, align) = place.to_ptr_align();
let mut new_value = Value::ByRef(ptr, align);
new_value = ecx.try_read_by_ref(new_value, layout.ty)?;
use rustc_data_structures::indexed_vec::Idx;
match (value, new_value) {
(Value::Scalar(_), Value::ByRef(..)) |
(Value::ScalarPair(..), Value::ByRef(..)) |
(Value::Scalar(_), Value::ScalarPair(..)) => bug!(
"field {} of {:?} yielded {:?}",
field.index(),
value,
new_value,
),
_ => {},
}
Ok(value_to_const_value(&ecx, new_value, layout.ty))
})();
result.map_err(|err| {
let (trace, span) = ecx.generate_stacktrace(None);
let err = ErrKind::Miri(err, trace);
ConstEvalErr {
kind: err.into(),
span,
}
})
}
pub fn const_variant_index<'a, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
param_env: ty::ParamEnv<'tcx>,
instance: ty::Instance<'tcx>,
val: ConstValue<'tcx>,
ty: Ty<'tcx>,
) -> EvalResult<'tcx, usize> {
trace!("const_variant_index: {:?}, {:?}, {:?}", instance, val, ty);
let mut ecx = mk_eval_cx(tcx, instance, param_env).unwrap();
let value = ecx.const_value_to_value(val, ty)?;
let (ptr, align) = match value {
Value::ScalarPair(..) | Value::Scalar(_) => {
let layout = ecx.layout_of(ty)?;
let ptr = ecx.memory.allocate(layout.size, layout.align, Some(MemoryKind::Stack))?.into();
ecx.write_value_to_ptr(value, ptr, layout.align, ty)?;
(ptr, layout.align)
},
Value::ByRef(ptr, align) => (ptr, align),
};
let place = Place::from_scalar_ptr(ptr, align);
ecx.read_discriminant_as_variant_index(place, ty)
}
pub fn const_value_to_allocation_provider<'a, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
(val, ty): (ConstValue<'tcx>, Ty<'tcx>),
) -> &'tcx Allocation {
match val {
ConstValue::ByRef(alloc, offset) => {
assert_eq!(offset.bytes(), 0);
return alloc;
},
_ => ()
}
let result = || -> EvalResult<'tcx, &'tcx Allocation> {
let mut ecx = EvalContext::new(
tcx.at(DUMMY_SP),
ty::ParamEnv::reveal_all(),
CompileTimeEvaluator,
());
let value = ecx.const_value_to_value(val, ty)?;
let layout = ecx.layout_of(ty)?;
let ptr = ecx.memory.allocate(layout.size, layout.align, Some(MemoryKind::Stack))?;
ecx.write_value_to_ptr(value, ptr.into(), layout.align, ty)?;
let alloc = ecx.memory.get(ptr.alloc_id)?;
Ok(tcx.intern_const_alloc(alloc.clone()))
};
result().expect("unable to convert ConstVal to Allocation")
}
pub fn const_eval_provider<'a, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>,
) -> ::rustc::middle::const_val::EvalResult<'tcx> {
trace!("const eval: {:?}", key);
let cid = key.value;
let def_id = cid.instance.def.def_id();
if let Some(id) = tcx.hir.as_local_node_id(def_id) {
let tables = tcx.typeck_tables_of(def_id);
let span = tcx.def_span(def_id);
// Do match-check before building MIR
if tcx.check_match(def_id).is_err() {
return Err(ConstEvalErr {
kind: Lrc::new(CheckMatchError),
span,
});
}
if let hir::BodyOwnerKind::Const = tcx.hir.body_owner_kind(id) {
tcx.mir_const_qualif(def_id);
}
// Do not continue into miri if typeck errors occurred; it will fail horribly
if tables.tainted_by_errors {
return Err(ConstEvalErr {
kind: Lrc::new(TypeckError),
span,
});
}
};
let (res, ecx) = eval_body_and_ecx(tcx, cid, None, key.param_env);
res.and_then(|(mut val, _, miri_ty)| {
if tcx.is_static(def_id).is_none() {
val = ecx.try_read_by_ref(val, miri_ty)?;
}
Ok(value_to_const_value(&ecx, val, miri_ty))
}).map_err(|mut err| {
if tcx.is_static(def_id).is_some() {
ecx.report(&mut err, true, None);
}
let (trace, span) = ecx.generate_stacktrace(None);
let err = ErrKind::Miri(err, trace);
ConstEvalErr {
kind: err.into(),
span,
}
})
}
fn numeric_intrinsic<'tcx>(
name: &str,
bits: u128,
kind: Primitive,
) -> EvalResult<'tcx, Scalar> {
let defined = match kind {
Primitive::Int(integer, _) => integer.size().bits() as u8,
_ => bug!("invalid `{}` argument: {:?}", name, bits),
};
let extra = 128 - defined as u128;
let bits_out = match name {
"ctpop" => bits.count_ones() as u128,
"ctlz" => bits.leading_zeros() as u128 - extra,
"cttz" => (bits << extra).trailing_zeros() as u128 - extra,
"bswap" => (bits << extra).swap_bytes(),
_ => bug!("not a numeric intrinsic: {}", name),
};
Ok(Scalar::Bits { bits: bits_out, defined })
}