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https://github.com/carbon-language/carbon-lang.git
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David Blaikie
4739828cca
Fixes #5186 With @zygoloid's kind assistance, this generalizes the existing non-const lowering of ClassInit, that had previously only handled InitializeFrom, to find other cases - such as a nested ClassInit used to initialize a class member. This refactors the `FindReturnSlotArgForInitializer` from `check/convert.cpp` into `sem_ir/file.{h,cpp}` for use from lowering (since lower doesn't depend on check, which I assume is an intentional layering constraint - so figured it made sense to move it to sem_ir, and found one or two similar-ish utility functions in `sem_ir/file.{h,cpp}`, so figured that was a good spot)
291 lines
12 KiB
C++
291 lines
12 KiB
C++
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/ADT/Twine.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/Value.h"
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#include "toolchain/lower/function_context.h"
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#include "toolchain/sem_ir/expr_info.h"
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#include "toolchain/sem_ir/file.h"
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#include "toolchain/sem_ir/inst.h"
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#include "toolchain/sem_ir/typed_insts.h"
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namespace Carbon::Lower {
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auto HandleInst(FunctionContext& /*context*/, SemIR::InstId /*inst_id*/,
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SemIR::ClassDecl /*inst*/) -> void {
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// No action to perform.
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}
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// Extracts an element of an aggregate, such as a struct, tuple, or class, by
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// index. Depending on the expression category and value representation of the
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// aggregate input, this will either produce a value or a reference.
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static auto GetAggregateElement(FunctionContext& context,
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SemIR::InstId aggr_inst_id,
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SemIR::ElementIndex idx,
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SemIR::TypeId result_type_id, llvm::Twine name)
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-> llvm::Value* {
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auto aggr_inst = context.sem_ir().insts().Get(aggr_inst_id);
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auto* aggr_value = context.GetValue(aggr_inst_id);
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switch (SemIR::GetExprCategory(context.sem_ir(), aggr_inst_id)) {
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case SemIR::ExprCategory::Error:
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case SemIR::ExprCategory::NotExpr:
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case SemIR::ExprCategory::Initializing:
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case SemIR::ExprCategory::Mixed:
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CARBON_FATAL("Unexpected expression category for aggregate access");
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case SemIR::ExprCategory::Value: {
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auto value_rep =
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SemIR::ValueRepr::ForType(context.sem_ir(), aggr_inst.type_id());
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CARBON_CHECK(value_rep.aggregate_kind != SemIR::ValueRepr::NotAggregate,
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"aggregate type should have aggregate value representation");
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switch (value_rep.kind) {
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case SemIR::ValueRepr::Unknown:
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CARBON_FATAL("Lowering access to incomplete aggregate type");
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case SemIR::ValueRepr::None:
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return aggr_value;
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case SemIR::ValueRepr::Copy:
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// We are holding the values of the aggregate directly, elementwise.
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return context.builder().CreateExtractValue(aggr_value, idx.index,
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name);
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case SemIR::ValueRepr::Pointer: {
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// The value representation is a pointer to an aggregate that we want
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// to index into.
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auto pointee_type_id =
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context.sem_ir().GetPointeeType(value_rep.type_id);
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auto* value_type = context.GetType(pointee_type_id);
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auto* elem_ptr = context.builder().CreateStructGEP(
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value_type, aggr_value, idx.index, name);
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if (!value_rep.elements_are_values()) {
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// `elem_ptr` points to an object representation, which is our
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// result.
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return elem_ptr;
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}
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// `elem_ptr` points to a value representation. Load it.
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auto result_value_type_id =
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SemIR::ValueRepr::ForType(context.sem_ir(), result_type_id)
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.type_id;
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return context.builder().CreateLoad(
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context.GetType(result_value_type_id), elem_ptr, name + ".load");
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}
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case SemIR::ValueRepr::Custom:
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CARBON_FATAL(
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"Aggregate should never have custom value representation");
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}
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}
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case SemIR::ExprCategory::DurableRef:
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case SemIR::ExprCategory::EphemeralRef: {
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// Just locate the aggregate element.
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auto* aggr_type = context.GetType(aggr_inst.type_id());
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return context.builder().CreateStructGEP(aggr_type, aggr_value, idx.index,
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name);
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}
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}
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}
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static auto GetStructFieldName(FunctionContext& context,
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SemIR::TypeId struct_type_id,
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SemIR::ElementIndex index) -> llvm::StringRef {
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auto struct_type =
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context.sem_ir().types().GetAs<SemIR::StructType>(struct_type_id);
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auto fields =
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context.sem_ir().struct_type_fields().Get(struct_type.fields_id);
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return context.sem_ir().names().GetIRBaseName(fields[index.index].name_id);
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}
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auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
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SemIR::ClassElementAccess inst) -> void {
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// Find the class that we're performing access into.
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auto class_type_id = context.sem_ir().insts().Get(inst.base_id).type_id();
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SemIR::TypeId object_repr_id =
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context.sem_ir().types().GetObjectRepr(class_type_id);
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// Translate the class field access into a struct access on the object
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// representation.
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context.SetLocal(
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inst_id, GetAggregateElement(
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context, inst.base_id, inst.index, inst.type_id,
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GetStructFieldName(context, object_repr_id, inst.index)));
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}
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static auto EmitAggregateInitializer(FunctionContext& context,
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SemIR::TypeId type_id,
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SemIR::InstBlockId refs_id,
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llvm::Twine name) -> llvm::Value* {
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auto* llvm_type = context.GetType(type_id);
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auto refs = context.sem_ir().inst_blocks().Get(refs_id);
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switch (SemIR::InitRepr::ForType(context.sem_ir(), type_id).kind) {
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case SemIR::InitRepr::None: {
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// TODO: Add a helper to poison a value slot.
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return llvm::PoisonValue::get(llvm_type);
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}
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case SemIR::InitRepr::InPlace: {
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// Finish initialization of constant fields. We will have skipped this
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// when emitting the initializers because they have constant values.
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//
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// TODO: This emits the initializers for constant fields after all
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// initialization of non-constant fields. This may be observable in some
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// ways such as under a debugger in a debug build. It would be preferable
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// to initialize the constant portions of the aggregate first, but this
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// will likely need a change to the SemIR representation.
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//
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// TODO: If most of the bytes of the result have known constant values,
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// it'd be nice to emit a memcpy from a constant followed by the
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// non-constant initialization.
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for (auto [i, ref_id] : llvm::enumerate(refs)) {
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if (context.sem_ir().constant_values().Get(ref_id).is_constant()) {
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auto dest_id =
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SemIR::FindReturnSlotArgForInitializer(context.sem_ir(), ref_id);
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auto src_id = ref_id;
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auto storage_type_id =
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context.sem_ir().insts().Get(dest_id).type_id();
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context.FinishInit(storage_type_id, dest_id, src_id);
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}
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}
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// TODO: Add a helper to poison a value slot.
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return llvm::PoisonValue::get(llvm_type);
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}
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case SemIR::InitRepr::ByCopy: {
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auto refs = context.sem_ir().inst_blocks().Get(refs_id);
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CARBON_CHECK(
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refs.size() == 1,
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"Unexpected size for aggregate with by-copy value representation");
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// TODO: Remove the LLVM StructType wrapper in this case, so we don't
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// need this `insert_value` wrapping.
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return context.builder().CreateInsertValue(
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llvm::PoisonValue::get(llvm_type), context.GetValue(refs[0]), {0},
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name);
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}
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case SemIR::InitRepr::Incomplete:
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CARBON_FATAL("Lowering aggregate initialization of incomplete type {0}",
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context.sem_ir().types().GetAsInst(type_id));
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}
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}
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auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
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SemIR::ClassInit inst) -> void {
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context.SetLocal(
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inst_id, EmitAggregateInitializer(context, inst.type_id, inst.elements_id,
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"class.init"));
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}
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auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
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SemIR::StructAccess inst) -> void {
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auto struct_type_id = context.sem_ir().insts().Get(inst.struct_id).type_id();
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context.SetLocal(
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inst_id, GetAggregateElement(
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context, inst.struct_id, inst.index, inst.type_id,
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GetStructFieldName(context, struct_type_id, inst.index)));
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}
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auto HandleInst(FunctionContext& /*context*/, SemIR::InstId /*inst_id*/,
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SemIR::StructLiteral /*inst*/) -> void {
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// A StructLiteral should always be converted to a StructInit or StructValue
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// if its value is needed.
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}
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// Emits the value representation for a struct or tuple whose elements are the
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// contents of `refs_id`.
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static auto EmitAggregateValueRepr(FunctionContext& context,
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SemIR::TypeId type_id,
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SemIR::InstBlockId refs_id) -> llvm::Value* {
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auto value_rep = SemIR::ValueRepr::ForType(context.sem_ir(), type_id);
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switch (value_rep.kind) {
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case SemIR::ValueRepr::Unknown:
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CARBON_FATAL("Incomplete aggregate type in lowering");
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case SemIR::ValueRepr::None:
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// TODO: Add a helper to get a "no value representation" value.
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return llvm::PoisonValue::get(context.GetType(value_rep.type_id));
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case SemIR::ValueRepr::Copy: {
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auto refs = context.sem_ir().inst_blocks().Get(refs_id);
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CARBON_CHECK(
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refs.size() == 1,
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"Unexpected size for aggregate with by-copy value representation");
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// TODO: Remove the LLVM StructType wrapper in this case, so we don't
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// need this `insert_value` wrapping.
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return context.builder().CreateInsertValue(
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llvm::PoisonValue::get(context.GetType(value_rep.type_id)),
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context.GetValue(refs[0]), {0});
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}
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case SemIR::ValueRepr::Pointer: {
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auto pointee_type_id = context.sem_ir().GetPointeeType(value_rep.type_id);
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auto* llvm_value_rep_type = context.GetType(pointee_type_id);
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// Write the value representation to a local alloca so we can produce a
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// pointer to it as the value representation of the struct or tuple.
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auto* alloca = context.builder().CreateAlloca(llvm_value_rep_type);
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for (auto [i, ref] :
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llvm::enumerate(context.sem_ir().inst_blocks().Get(refs_id))) {
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context.builder().CreateStore(
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context.GetValue(ref),
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context.builder().CreateStructGEP(llvm_value_rep_type, alloca, i));
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}
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return alloca;
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}
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case SemIR::ValueRepr::Custom:
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CARBON_FATAL("Aggregate should never have custom value representation");
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}
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}
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auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
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SemIR::StructInit inst) -> void {
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context.SetLocal(
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inst_id, EmitAggregateInitializer(context, inst.type_id, inst.elements_id,
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"struct.init"));
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}
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auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
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SemIR::StructValue inst) -> void {
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if (auto fn_type = context.sem_ir().types().TryGetAs<SemIR::FunctionType>(
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inst.type_id)) {
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context.SetLocal(inst_id, context.GetFunction(fn_type->function_id));
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return;
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}
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context.SetLocal(
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inst_id, EmitAggregateValueRepr(context, inst.type_id, inst.elements_id));
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}
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auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
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SemIR::TupleAccess inst) -> void {
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context.SetLocal(inst_id,
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GetAggregateElement(context, inst.tuple_id, inst.index,
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inst.type_id, "tuple.elem"));
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}
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auto HandleInst(FunctionContext& /*context*/, SemIR::InstId /*inst_id*/,
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SemIR::TupleLiteral /*inst*/) -> void {
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// A TupleLiteral should always be converted to a TupleInit or TupleValue if
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// its value is needed.
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}
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auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
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SemIR::TupleInit inst) -> void {
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context.SetLocal(
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inst_id, EmitAggregateInitializer(context, inst.type_id, inst.elements_id,
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"tuple.init"));
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}
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auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
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SemIR::TupleValue inst) -> void {
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context.SetLocal(
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inst_id, EmitAggregateValueRepr(context, inst.type_id, inst.elements_id));
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}
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} // namespace Carbon::Lower
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