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Refactor function return type representation (#6463)

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This separates the return type from the return pattern, and replaces the
return pattern with a block of return patterns. This is a step toward
support for `ref` returns (where there's no corresponding return
pattern) and compund-form returns (where there may be multiple return
patterns).
This commit is contained in:
Geoff Romer
2025-12-10 18:34:23 +00:00
committed by GitHub
parent 77918d023b
commit bf45b1cbf5
57 changed files with 1668 additions and 1532 deletions
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toolchain/check/cpp/thunk.cpp
+15 -10
View File
@@ -559,19 +559,26 @@ auto PerformCppThunkCall(Context& context, SemIR::LocId loc_id,
auto& callee_function = context.functions().Get(callee_function_id);
auto callee_function_params =
context.inst_blocks().Get(callee_function.call_params_id);
auto callee_return_patterns =
context.inst_blocks().GetOrEmpty(callee_function.return_patterns_id);
auto thunk_callee = GetCalleeAsFunction(context.sem_ir(), thunk_callee_id);
auto& thunk_function = context.functions().Get(thunk_callee.function_id);
auto thunk_function_params =
context.inst_blocks().Get(thunk_function.call_params_id);
auto thunk_return_patterns =
context.inst_blocks().GetOrEmpty(thunk_function.return_patterns_id);
CARBON_CHECK(
callee_return_patterns.size() <= 1 && thunk_return_patterns.size() <= 1,
"TODO: generalize this logic to support multiple return patterns.");
// Whether we need to pass a return address to the thunk as a final argument.
bool thunk_takes_return_address =
callee_function.return_slot_pattern_id.has_value() &&
!thunk_function.return_slot_pattern_id.has_value();
!callee_return_patterns.empty() && thunk_return_patterns.empty();
// The number of arguments we should be acquiring in order to call the thunk.
// This includes the return address parameter, if any.
// This includes the return address parameters, if any.
unsigned num_thunk_args =
context.inst_blocks().Get(thunk_function.param_patterns_id).size();
@@ -585,15 +592,13 @@ auto PerformCppThunkCall(Context& context, SemIR::LocId loc_id,
return_slot_id = callee_arg_ids.consume_back();
}
// If there's a return slot pattern, drop the corresponding parameter.
// If there are return slot patterns, drop the corresponding parameters.
// TODO: The parameter should probably only be created if the return pattern
// actually needs a return address to be passed in.
if (thunk_function.return_slot_pattern_id.has_value()) {
thunk_function_params.consume_back();
}
if (callee_function.return_slot_pattern_id.has_value()) {
callee_function_params.consume_back();
}
thunk_function_params =
thunk_function_params.drop_back(thunk_return_patterns.size());
callee_function_params =
callee_function_params.drop_back(callee_return_patterns.size());
// We assume that the call parameters exactly match the parameter patterns for
// both the thunk and the callee. This is currently guaranteed because we only