bjoernager/rust
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Only memoize const fn calls during const eval

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Miri and other engines may want to execute the function in order to detect UB inside of them.
This commit is contained in:
Oliver Scherer 2019-11-29 11:57:17 +01:00
parent 4752c05af4
commit 735a610f47
2 changed files with 15 additions and 13 deletions
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14
src/librustc_mir/const_eval.rs
View file

@ -336,6 +336,20 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
_unwind: Option<mir::BasicBlock> // unwinding is not supported in consts
) -> InterpResult<'tcx, Option<&'mir mir::Body<'tcx>>> {
debug!("eval_fn_call: {:?}", instance);
// If this function is a `const fn` then as an optimization we can query this
// evaluation immediately.
//
// For the moment we only do this for functions which take no arguments
// (or all arguments are ZSTs) so that we don't memoize too much.
if ecx.tcx.is_const_fn_raw(instance.def.def_id()) &&
args.iter().all(|a| a.layout.is_zst())
{
let gid = GlobalId { instance, promoted: None };
ecx.eval_const_fn_call(gid, ret)?;
return Ok(None);
}
// Only check non-glue functions
if let ty::InstanceDef::Item(def_id) = instance.def {
// Execution might have wandered off into other crates, so we cannot do a stability-

14
src/librustc_mir/interpret/terminator.rs
View file

@ -284,18 +284,6 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
ty::InstanceDef::DropGlue(..) |
ty::InstanceDef::CloneShim(..) |
ty::InstanceDef::Item(_) => {
// If this function is a `const fn` then as an optimization we can query this
// evaluation immediately.
//
// For the moment we only do this for functions which take no arguments
// (or all arguments are ZSTs) so that we don't memoize too much.
if self.tcx.is_const_fn_raw(instance.def.def_id()) &&
args.iter().all(|a| a.layout.is_zst())
{
let gid = GlobalId { instance, promoted: None };
return self.eval_const_fn_call(gid, ret);
}
// We need MIR for this fn
let body = match M::find_fn(self, instance, args, ret, unwind)? {
Some(body) => body,
@ -463,7 +451,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
/// Evaluate a const function where all arguments (if any) are zero-sized types.
/// The evaluation is memoized thanks to the query system.
fn eval_const_fn_call(
pub (crate) fn eval_const_fn_call(
&mut self,
gid: GlobalId<'tcx>,
ret: Option<(PlaceTy<'tcx, M::PointerTag>, mir::BasicBlock)>,