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Explain the actual reason why stripping binders is fine

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This commit is contained in:
Oli Scherer 2025-02-24 09:22:41 +00:00
parent 2c6a12ec44
commit ff5a8ad2ab
1 changed files with 5 additions and 6 deletions
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11
compiler/rustc_monomorphize/src/partitioning/autodiff.rs
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@ -12,15 +12,14 @@ fn adjust_activity_to_abi<'tcx>(tcx: TyCtxt<'tcx>, fn_ty: Ty<'tcx>, da: &mut Vec
if !matches!(fn_ty.kind(), ty::FnDef(..)) {
bug!("expected fn def for autodiff, got {:?}", fn_ty);
}
let fnc_binder: ty::Binder<'_, ty::FnSig<'_>> = fn_ty.fn_sig(tcx);
// If rustc compiles the unmodified primal, we know that this copy of the function
// also has correct lifetimes. We know that Enzyme won't free the shadow too early
// (or actually at all), so let's strip lifetimes when computing the layout.
let x = tcx.instantiate_bound_regions_with_erased(fnc_binder);
// We don't actually pass the types back into the type system.
// All we do is decide how to handle the arguments.
let sig = fn_ty.fn_sig(tcx).skip_binder();
let mut new_activities = vec![];
let mut new_positions = vec![];
for (i, ty) in x.inputs().iter().enumerate() {
for (i, ty) in sig.inputs().iter().enumerate() {
if let Some(inner_ty) = ty.builtin_deref(true) {
if ty.is_fn_ptr() {
// FIXME(ZuseZ4): add a nicer error, or just figure out how to support them,