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Don't actually create a full MIR stack frame when not needed #57351

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Merged
merged 6 commits into from
Jan 13, 2019
Merged

Don't actually create a full MIR stack frame when not needed #57351

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c0f0f45
Don't actually create a full MIR stack frame when not needed
oli-obk Jan 5, 2019
14e662d
Manually push a stack frame where no valid frame is needed
oli-obk Jan 8, 2019
cea282b
Make `mk_eval_cx` private to const eval
oli-obk Jan 8, 2019
f174b73
Document the `mk_*_eval_cx` functions
oli-obk Jan 9, 2019
cd5a9e0
Explain the arguments of the `mk_*_eval_cx` functions
oli-obk Jan 9, 2019
dec79e4
Not seeing the forest because there are too many trees in the way
oli-obk Jan 9, 2019
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25 changes: 13 additions & 12 deletions src/librustc_mir/const_eval.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,16 @@ pub fn mk_borrowck_eval_cx<'a, 'mir, 'tcx>(
) -> EvalResult<'tcx, CompileTimeEvalContext<'a, 'mir, 'tcx>> {
debug!("mk_borrowck_eval_cx: {:?}", instance);
let param_env = tcx.param_env(instance.def_id());
mk_eval_cx_inner(tcx, instance, mir, span, param_env)
}

fn mk_eval_cx_inner<'a, 'mir, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
instance: Instance<'tcx>,
mir: &'mir mir::Mir<'tcx>,
span: Span,
param_env: ty::ParamEnv<'tcx>,
) -> EvalResult<'tcx, CompileTimeEvalContext<'a, 'mir, 'tcx>> {
let mut ecx = EvalContext::new(tcx.at(span), param_env, CompileTimeInterpreter::new());
// insert a stack frame so any queries have the correct substs
// cannot use `push_stack_frame`; if we do `const_prop` explodes
Expand All @@ -60,24 +70,15 @@ pub fn mk_borrowck_eval_cx<'a, 'mir, 'tcx>(
Ok(ecx)
}

pub fn mk_eval_cx<'a, 'tcx>(
fn mk_eval_cx<'a, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
instance: Instance<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> EvalResult<'tcx, CompileTimeEvalContext<'a, 'tcx, 'tcx>> {
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, CompileTimeInterpreter::new());
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,
None,
StackPopCleanup::Goto(None), // never pop
)?;
Ok(ecx)
let mir = tcx.optimized_mir(instance.def.def_id());
mk_eval_cx_inner(tcx, instance, mir, span, param_env)
}

pub(crate) fn eval_promoted<'a, 'mir, 'tcx>(
Expand Down