src/abi/returning.rs

   1 use crate::abi::pass_mode::*;
   2 use crate::prelude::*;
   3
   4 fn return_layout<'a, 'tcx>(fx: &mut FunctionCx<'a, 'tcx, impl Backend>) -> TyAndLayout<'tcx> {
   5     fx.layout_of(fx.monomorphize(&fx.mir.local_decls[RETURN_PLACE].ty))
   6 }
   7
   8 pub(crate) fn can_return_to_ssa_var<'tcx>(tcx: TyCtxt<'tcx>, dest_layout: TyAndLayout<'tcx>) -> bool {
   9     match get_pass_mode(tcx, dest_layout) {
  10         PassMode::NoPass | PassMode::ByVal(_) => true,
  11         // FIXME Make it possible to return ByValPair and ByRef to an ssa var.
  12         PassMode::ByValPair(_, _) | PassMode::ByRef { size: _ } => false
  13     }
  14 }
  15
  16 pub(super) fn codegen_return_param(
  17     fx: &mut FunctionCx<'_, '_, impl Backend>,
  18     ssa_analyzed: &rustc_index::vec::IndexVec<Local, crate::analyze::SsaKind>,
  19     start_block: Block,
  20 ) {
  21     let ret_layout = return_layout(fx);
  22     let ret_pass_mode = get_pass_mode(fx.tcx, ret_layout);
  23     let ret_param = match ret_pass_mode {
  24         PassMode::NoPass => {
  25             fx.local_map
  26                 .insert(RETURN_PLACE, CPlace::no_place(ret_layout));
  27             Empty
  28         }
  29         PassMode::ByVal(_) | PassMode::ByValPair(_, _) => {
  30             let is_ssa = ssa_analyzed[RETURN_PLACE] == crate::analyze::SsaKind::Ssa;
  31
  32             super::local_place(fx, RETURN_PLACE, ret_layout, is_ssa);
  33
  34             Empty
  35         }
  36         PassMode::ByRef { size: Some(_) } => {
  37             let ret_param = fx.bcx.append_block_param(start_block, fx.pointer_type);
  38             fx.local_map
  39                 .insert(RETURN_PLACE, CPlace::for_ptr(Pointer::new(ret_param), ret_layout));
  40
  41             Single(ret_param)
  42         }
  43         PassMode::ByRef { size: None } => todo!(),
  44     };
  45
  46     #[cfg(not(debug_assertions))]
  47     let _ = ret_param;
  48
  49     #[cfg(debug_assertions)]
  50     crate::abi::comments::add_arg_comment(
  51         fx,
  52         "ret",
  53         Some(RETURN_PLACE),
  54         None,
  55         ret_param,
  56         ret_pass_mode,
  57         ret_layout.ty,
  58     );
  59 }
  60
  61 pub(super) fn codegen_with_call_return_arg<'tcx, B: Backend, T>(
  62     fx: &mut FunctionCx<'_, 'tcx, B>,
  63     fn_sig: FnSig<'tcx>,
  64     ret_place: Option<CPlace<'tcx>>,
  65     f: impl FnOnce(&mut FunctionCx<'_, 'tcx, B>, Option<Value>) -> (Inst, T),
  66 ) -> (Inst, T) {
  67     let ret_layout = fx.layout_of(fn_sig.output());
  68
  69     let output_pass_mode = get_pass_mode(fx.tcx, ret_layout);
  70     let return_ptr = match output_pass_mode {
  71         PassMode::NoPass => None,
  72         PassMode::ByRef { size: Some(_)} => match ret_place {
  73             Some(ret_place) => Some(ret_place.to_ptr().get_addr(fx)),
  74             None => Some(fx.bcx.ins().iconst(fx.pointer_type, 43)), // FIXME allocate temp stack slot
  75         },
  76         PassMode::ByRef { size: None } => todo!(),
  77         PassMode::ByVal(_) | PassMode::ByValPair(_, _) => None,
  78     };
  79
  80     let (call_inst, meta) = f(fx, return_ptr);
  81
  82     match output_pass_mode {
  83         PassMode::NoPass => {}
  84         PassMode::ByVal(_) => {
  85             if let Some(ret_place) = ret_place {
  86                 let ret_val = fx.bcx.inst_results(call_inst)[0];
  87                 ret_place.write_cvalue(fx, CValue::by_val(ret_val, ret_layout));
  88             }
  89         }
  90         PassMode::ByValPair(_, _) => {
  91             if let Some(ret_place) = ret_place {
  92                 let ret_val_a = fx.bcx.inst_results(call_inst)[0];
  93                 let ret_val_b = fx.bcx.inst_results(call_inst)[1];
  94                 ret_place.write_cvalue(fx, CValue::by_val_pair(ret_val_a, ret_val_b, ret_layout));
  95             }
  96         }
  97         PassMode::ByRef { size: Some(_) } => {}
  98         PassMode::ByRef { size: None } => todo!(),
  99     }
 100
 101     (call_inst, meta)
 102 }
 103
 104 pub(crate) fn codegen_return(fx: &mut FunctionCx<'_, '_, impl Backend>) {
 105     match get_pass_mode(fx.tcx, return_layout(fx)) {
 106         PassMode::NoPass | PassMode::ByRef { size: Some(_) } => {
 107             fx.bcx.ins().return_(&[]);
 108         }
 109         PassMode::ByRef { size: None } => todo!(),
 110         PassMode::ByVal(_) => {
 111             let place = fx.get_local_place(RETURN_PLACE);
 112             let ret_val = place.to_cvalue(fx).load_scalar(fx);
 113             fx.bcx.ins().return_(&[ret_val]);
 114         }
 115         PassMode::ByValPair(_, _) => {
 116             let place = fx.get_local_place(RETURN_PLACE);
 117             let (ret_val_a, ret_val_b) = place.to_cvalue(fx).load_scalar_pair(fx);
 118             fx.bcx.ins().return_(&[ret_val_a, ret_val_b]);
 119         }
 120     }
 121 }