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Move eval_const_fn_call to the const_eval module

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This commit is contained in:
Oliver Scherer 2019-12-25 01:08:39 +01:00
parent 2d67edd32c
commit 9a82458e70
2 changed files with 44 additions and 34 deletions
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55
src/librustc_mir/const_eval/machine.rs
View File

@ -149,18 +149,9 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
// sensitive check here. But we can at least rule out functions that are not const
// at all.
if ecx.tcx.is_const_fn_raw(def_id) {
// 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.
//
// Because `#[track_caller]` adds an implicit non-ZST argument, we also cannot
// perform this optimization on items tagged with it.
let no_implicit_args = !instance.def.requires_caller_location(ecx.tcx());
if args.iter().all(|a| a.layout.is_zst()) && no_implicit_args {
let gid = GlobalId { instance, promoted: None };
ecx.eval_const_fn_call(gid, ret)?;
// If this function is a `const fn` then under certain circumstances we
// can evaluate call via the query system, thus memoizing all future calls.
if ecx.try_eval_const_fn_call(instance, ret, args)? {
return Ok(None);
}
} else {
@ -326,3 +317,43 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
}
}
}
impl<'mir, 'tcx> InterpCx<'mir, 'tcx, CompileTimeInterpreter<'mir, 'tcx>> {
/// Evaluate a const function where all arguments (if any) are zero-sized types.
/// The evaluation is memoized thanks to the query system.
///
/// Returns `true` if the call has been evaluated.
fn try_eval_const_fn_call(
&mut self,
instance: ty::Instance<'tcx>,
ret: Option<(PlaceTy<'tcx>, mir::BasicBlock)>,
args: &[OpTy<'tcx>],
) -> InterpResult<'tcx, bool> {
trace!("try_eval_const_fn_call: {:?}", instance);
// Because `#[track_caller]` adds an implicit non-ZST argument, we also cannot
// perform this optimization on items tagged with it.
if instance.def.requires_caller_location(self.tcx()) {
return Ok(false);
}
// 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 args.iter().any(|a| !a.layout.is_zst()) {
return Ok(false);
}
let gid = GlobalId { instance, promoted: None };
let place = self.const_eval_raw(gid)?;
let dest = match ret {
Some((dest, _)) => dest,
// Don't memoize diverging function calls.
None => return Ok(false),
};
self.copy_op(place.into(), dest)?;
self.return_to_block(ret.map(|r| r.1))?;
self.dump_place(*dest);
return Ok(true);
}
}

23
src/librustc_mir/interpret/terminator.rs
View File

@ -7,8 +7,7 @@ use rustc_target::spec::abi::Abi;
use syntax::source_map::Span;
use super::{
FnVal, GlobalId, ImmTy, InterpCx, InterpResult, MPlaceTy, Machine, OpTy, PlaceTy,
StackPopCleanup,
FnVal, ImmTy, InterpCx, InterpResult, MPlaceTy, Machine, OpTy, PlaceTy, StackPopCleanup,
};
impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
@ -402,26 +401,6 @@ 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.
// FIXME: Consider moving this to `const_eval.rs`.
pub(crate) fn eval_const_fn_call(
&mut self,
gid: GlobalId<'tcx>,
ret: Option<(PlaceTy<'tcx, M::PointerTag>, mir::BasicBlock)>,
) -> InterpResult<'tcx> {
trace!("eval_const_fn_call: {:?}", gid);
let place = self.const_eval_raw(gid)?;
let dest = ret.ok_or_else(|| err_ub!(Unreachable))?.0;
self.copy_op(place.into(), dest)?;
self.return_to_block(ret.map(|r| r.1))?;
self.dump_place(*dest);
return Ok(());
}
fn drop_in_place(
&mut self,
place: PlaceTy<'tcx, M::PointerTag>,