diff options
Diffstat (limited to 'compiler/rustc_codegen_cranelift/src/abi/returning.rs')
| -rw-r--r-- | compiler/rustc_codegen_cranelift/src/abi/returning.rs | 141 |
1 files changed, 141 insertions, 0 deletions
diff --git a/compiler/rustc_codegen_cranelift/src/abi/returning.rs b/compiler/rustc_codegen_cranelift/src/abi/returning.rs new file mode 100644 index 000000000..ff3bb2dfd --- /dev/null +++ b/compiler/rustc_codegen_cranelift/src/abi/returning.rs @@ -0,0 +1,141 @@ +//! Return value handling + +use crate::prelude::*; + +use rustc_target::abi::call::{ArgAbi, PassMode}; +use smallvec::{smallvec, SmallVec}; + +/// Return a place where the return value of the current function can be written to. If necessary +/// this adds an extra parameter pointing to where the return value needs to be stored. +pub(super) fn codegen_return_param<'tcx>( + fx: &mut FunctionCx<'_, '_, 'tcx>, + ssa_analyzed: &rustc_index::vec::IndexVec<Local, crate::analyze::SsaKind>, + block_params_iter: &mut impl Iterator<Item = Value>, +) -> CPlace<'tcx> { + let (ret_place, ret_param): (_, SmallVec<[_; 2]>) = match fx.fn_abi.as_ref().unwrap().ret.mode { + PassMode::Ignore | PassMode::Direct(_) | PassMode::Pair(_, _) | PassMode::Cast(_) => { + let is_ssa = ssa_analyzed[RETURN_PLACE] == crate::analyze::SsaKind::Ssa; + ( + super::make_local_place( + fx, + RETURN_PLACE, + fx.fn_abi.as_ref().unwrap().ret.layout, + is_ssa, + ), + smallvec![], + ) + } + PassMode::Indirect { attrs: _, extra_attrs: None, on_stack: _ } => { + let ret_param = block_params_iter.next().unwrap(); + assert_eq!(fx.bcx.func.dfg.value_type(ret_param), fx.pointer_type); + ( + CPlace::for_ptr(Pointer::new(ret_param), fx.fn_abi.as_ref().unwrap().ret.layout), + smallvec![ret_param], + ) + } + PassMode::Indirect { attrs: _, extra_attrs: Some(_), on_stack: _ } => { + unreachable!("unsized return value") + } + }; + + crate::abi::comments::add_arg_comment( + fx, + "ret", + Some(RETURN_PLACE), + None, + &ret_param, + fx.fn_abi.as_ref().unwrap().ret.mode, + fx.fn_abi.as_ref().unwrap().ret.layout, + ); + + ret_place +} + +/// Invokes the closure with if necessary a value representing the return pointer. When the closure +/// returns the call return value(s) if any are written to the correct place. +pub(super) fn codegen_with_call_return_arg<'tcx>( + fx: &mut FunctionCx<'_, '_, 'tcx>, + ret_arg_abi: &ArgAbi<'tcx, Ty<'tcx>>, + ret_place: CPlace<'tcx>, + f: impl FnOnce(&mut FunctionCx<'_, '_, 'tcx>, Option<Value>) -> Inst, +) { + let (ret_temp_place, return_ptr) = match ret_arg_abi.mode { + PassMode::Ignore => (None, None), + PassMode::Indirect { attrs: _, extra_attrs: None, on_stack: _ } => { + if matches!(ret_place.inner(), CPlaceInner::Addr(_, None)) { + // This is an optimization to prevent unnecessary copies of the return value when + // the return place is already a memory place as opposed to a register. + // This match arm can be safely removed. + (None, Some(ret_place.to_ptr().get_addr(fx))) + } else { + let place = CPlace::new_stack_slot(fx, ret_arg_abi.layout); + (Some(place), Some(place.to_ptr().get_addr(fx))) + } + } + PassMode::Indirect { attrs: _, extra_attrs: Some(_), on_stack: _ } => { + unreachable!("unsized return value") + } + PassMode::Direct(_) | PassMode::Pair(_, _) | PassMode::Cast(_) => (None, None), + }; + + let call_inst = f(fx, return_ptr); + + match ret_arg_abi.mode { + PassMode::Ignore => {} + PassMode::Direct(_) => { + let ret_val = fx.bcx.inst_results(call_inst)[0]; + ret_place.write_cvalue(fx, CValue::by_val(ret_val, ret_arg_abi.layout)); + } + PassMode::Pair(_, _) => { + let ret_val_a = fx.bcx.inst_results(call_inst)[0]; + let ret_val_b = fx.bcx.inst_results(call_inst)[1]; + ret_place + .write_cvalue(fx, CValue::by_val_pair(ret_val_a, ret_val_b, ret_arg_abi.layout)); + } + PassMode::Cast(cast) => { + let results = + fx.bcx.inst_results(call_inst).iter().copied().collect::<SmallVec<[Value; 2]>>(); + let result = + super::pass_mode::from_casted_value(fx, &results, ret_place.layout(), cast); + ret_place.write_cvalue(fx, result); + } + PassMode::Indirect { attrs: _, extra_attrs: None, on_stack: _ } => { + if let Some(ret_temp_place) = ret_temp_place { + // If ret_temp_place is None, it is not necessary to copy the return value. + let ret_temp_value = ret_temp_place.to_cvalue(fx); + ret_place.write_cvalue(fx, ret_temp_value); + } + } + PassMode::Indirect { attrs: _, extra_attrs: Some(_), on_stack: _ } => { + unreachable!("unsized return value") + } + } +} + +/// Codegen a return instruction with the right return value(s) if any. +pub(crate) fn codegen_return(fx: &mut FunctionCx<'_, '_, '_>) { + match fx.fn_abi.as_ref().unwrap().ret.mode { + PassMode::Ignore | PassMode::Indirect { attrs: _, extra_attrs: None, on_stack: _ } => { + fx.bcx.ins().return_(&[]); + } + PassMode::Indirect { attrs: _, extra_attrs: Some(_), on_stack: _ } => { + unreachable!("unsized return value") + } + PassMode::Direct(_) => { + let place = fx.get_local_place(RETURN_PLACE); + let ret_val = place.to_cvalue(fx).load_scalar(fx); + fx.bcx.ins().return_(&[ret_val]); + } + PassMode::Pair(_, _) => { + let place = fx.get_local_place(RETURN_PLACE); + let (ret_val_a, ret_val_b) = place.to_cvalue(fx).load_scalar_pair(fx); + fx.bcx.ins().return_(&[ret_val_a, ret_val_b]); + } + PassMode::Cast(cast) => { + let place = fx.get_local_place(RETURN_PLACE); + let ret_val = place.to_cvalue(fx); + let ret_vals = super::pass_mode::to_casted_value(fx, ret_val, cast); + fx.bcx.ins().return_(&ret_vals); + } + } +} |