131 lines
4.8 KiB
Rust
131 lines
4.8 KiB
Rust
//! Return value handling
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use crate::abi::pass_mode::*;
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use crate::prelude::*;
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fn return_layout<'a, 'tcx>(fx: &mut FunctionCx<'a, 'tcx, impl Backend>) -> TyAndLayout<'tcx> {
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fx.layout_of(fx.monomorphize(&fx.mir.local_decls[RETURN_PLACE].ty))
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}
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/// Can the given type be returned into an ssa var or does it need to be returned on the stack.
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pub(crate) fn can_return_to_ssa_var<'tcx>(
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tcx: TyCtxt<'tcx>,
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dest_layout: TyAndLayout<'tcx>,
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) -> bool {
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match get_pass_mode(tcx, dest_layout) {
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PassMode::NoPass | PassMode::ByVal(_) | PassMode::ByValPair(_, _) => true,
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// FIXME Make it possible to return ByRef to an ssa var.
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PassMode::ByRef { size: _ } => false,
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}
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}
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/// Return a place where the return value of the current function can be written to. If necessary
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/// this adds an extra parameter pointing to where the return value needs to be stored.
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pub(super) fn codegen_return_param<'tcx>(
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fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
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ssa_analyzed: &rustc_index::vec::IndexVec<Local, crate::analyze::SsaKind>,
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start_block: Block,
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) -> CPlace<'tcx> {
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let ret_layout = return_layout(fx);
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let ret_pass_mode = get_pass_mode(fx.tcx, ret_layout);
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let (ret_place, ret_param) = match ret_pass_mode {
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PassMode::NoPass => (CPlace::no_place(ret_layout), Empty),
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PassMode::ByVal(_) | PassMode::ByValPair(_, _) => {
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let is_ssa = ssa_analyzed[RETURN_PLACE] == crate::analyze::SsaKind::Ssa;
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(
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super::make_local_place(fx, RETURN_PLACE, ret_layout, is_ssa),
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Empty,
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)
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}
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PassMode::ByRef { size: Some(_) } => {
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let ret_param = fx.bcx.append_block_param(start_block, fx.pointer_type);
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(
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CPlace::for_ptr(Pointer::new(ret_param), ret_layout),
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Single(ret_param),
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)
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}
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PassMode::ByRef { size: None } => todo!(),
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};
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#[cfg(not(debug_assertions))]
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let _ = ret_param;
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#[cfg(debug_assertions)]
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crate::abi::comments::add_arg_comment(
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fx,
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"ret",
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Some(RETURN_PLACE),
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None,
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ret_param,
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ret_pass_mode,
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ret_layout.ty,
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);
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ret_place
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}
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/// Invokes the closure with if necessary a value representing the return pointer. When the closure
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/// returns the call return value(s) if any are written to the correct place.
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pub(super) fn codegen_with_call_return_arg<'tcx, B: Backend, T>(
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fx: &mut FunctionCx<'_, 'tcx, B>,
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fn_sig: FnSig<'tcx>,
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ret_place: Option<CPlace<'tcx>>,
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f: impl FnOnce(&mut FunctionCx<'_, 'tcx, B>, Option<Value>) -> (Inst, T),
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) -> (Inst, T) {
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let ret_layout = fx.layout_of(fn_sig.output());
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let output_pass_mode = get_pass_mode(fx.tcx, ret_layout);
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let return_ptr = match output_pass_mode {
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PassMode::NoPass => None,
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PassMode::ByRef { size: Some(_) } => match ret_place {
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Some(ret_place) => Some(ret_place.to_ptr().get_addr(fx)),
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None => Some(fx.bcx.ins().iconst(fx.pointer_type, 43)), // FIXME allocate temp stack slot
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},
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PassMode::ByRef { size: None } => todo!(),
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PassMode::ByVal(_) | PassMode::ByValPair(_, _) => None,
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};
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let (call_inst, meta) = f(fx, return_ptr);
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match output_pass_mode {
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PassMode::NoPass => {}
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PassMode::ByVal(_) => {
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if let Some(ret_place) = ret_place {
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let ret_val = fx.bcx.inst_results(call_inst)[0];
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ret_place.write_cvalue(fx, CValue::by_val(ret_val, ret_layout));
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}
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}
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PassMode::ByValPair(_, _) => {
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if let Some(ret_place) = ret_place {
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let ret_val_a = fx.bcx.inst_results(call_inst)[0];
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let ret_val_b = fx.bcx.inst_results(call_inst)[1];
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ret_place.write_cvalue(fx, CValue::by_val_pair(ret_val_a, ret_val_b, ret_layout));
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}
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}
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PassMode::ByRef { size: Some(_) } => {}
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PassMode::ByRef { size: None } => todo!(),
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}
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(call_inst, meta)
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}
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/// Codegen a return instruction with the right return value(s) if any.
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pub(crate) fn codegen_return(fx: &mut FunctionCx<'_, '_, impl Backend>) {
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match get_pass_mode(fx.tcx, return_layout(fx)) {
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PassMode::NoPass | PassMode::ByRef { size: Some(_) } => {
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fx.bcx.ins().return_(&[]);
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}
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PassMode::ByRef { size: None } => todo!(),
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PassMode::ByVal(_) => {
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let place = fx.get_local_place(RETURN_PLACE);
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let ret_val = place.to_cvalue(fx).load_scalar(fx);
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fx.bcx.ins().return_(&[ret_val]);
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}
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PassMode::ByValPair(_, _) => {
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let place = fx.get_local_place(RETURN_PLACE);
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let (ret_val_a, ret_val_b) = place.to_cvalue(fx).load_scalar_pair(fx);
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fx.bcx.ins().return_(&[ret_val_a, ret_val_b]);
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}
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}
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}
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