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carbon-lang/toolchain/lower/handle.cpp
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// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Sequence.h"
#include "toolchain/lower/function_context.h"
#include "toolchain/sem_ir/inst.h"
#include "toolchain/sem_ir/inst_kind.h"
namespace Carbon::Lower {
auto HandleCrossReference(FunctionContext& /*context*/,
SemIR::InstId /*inst_id*/, SemIR::CrossReference inst)
-> void {
CARBON_FATAL() << "TODO: Add support: " << inst;
}
auto HandleAddressOf(FunctionContext& context, SemIR::InstId inst_id,
SemIR::AddressOf inst) -> void {
context.SetLocal(inst_id, context.GetLocal(inst.lvalue_id));
}
auto HandleArrayIndex(FunctionContext& context, SemIR::InstId inst_id,
SemIR::ArrayIndex inst) -> void {
auto* array_value = context.GetLocal(inst.array_id);
auto* llvm_type =
context.GetType(context.sem_ir().insts().Get(inst.array_id).type_id());
llvm::Value* indexes[2] = {
llvm::ConstantInt::get(llvm::Type::getInt32Ty(context.llvm_context()), 0),
context.GetLocal(inst.index_id)};
context.SetLocal(inst_id,
context.builder().CreateInBoundsGEP(llvm_type, array_value,
indexes, "array.index"));
}
auto HandleArrayInit(FunctionContext& context, SemIR::InstId inst_id,
SemIR::ArrayInit inst) -> void {
// The result of initialization is the return slot of the initializer.
context.SetLocal(inst_id,
context.GetLocal(context.sem_ir()
.inst_blocks()
.Get(inst.inits_and_return_slot_id)
.back()));
}
auto HandleAssign(FunctionContext& context, SemIR::InstId /*inst_id*/,
SemIR::Assign inst) -> void {
auto storage_type_id = context.sem_ir().insts().Get(inst.lhs_id).type_id();
context.FinishInitialization(storage_type_id, inst.lhs_id, inst.rhs_id);
}
auto HandleBinaryOperatorAdd(FunctionContext& /*context*/,
SemIR::InstId /*inst_id*/,
SemIR::BinaryOperatorAdd inst) -> void {
CARBON_FATAL() << "TODO: Add support: " << inst;
}
auto HandleBindName(FunctionContext& context, SemIR::InstId inst_id,
SemIR::BindName inst) -> void {
context.SetLocal(inst_id, context.GetLocal(inst.value_id));
}
auto HandleBlockArg(FunctionContext& context, SemIR::InstId inst_id,
SemIR::BlockArg inst) -> void {
context.SetLocal(inst_id, context.GetBlockArg(inst.block_id, inst.type_id));
}
auto HandleBoolLiteral(FunctionContext& context, SemIR::InstId inst_id,
SemIR::BoolLiteral inst) -> void {
llvm::Value* v =
llvm::ConstantInt::get(context.builder().getInt1Ty(), inst.value.index);
context.SetLocal(inst_id, v);
}
auto HandleBoundMethod(FunctionContext& context, SemIR::InstId inst_id,
SemIR::BoundMethod inst) -> void {
// Propagate just the function; the object is separately provided to the
// enclosing call as an implicit argument.
context.SetLocal(inst_id, context.GetLocalOrGlobal(inst.function_id));
}
auto HandleBranch(FunctionContext& context, SemIR::InstId /*inst_id*/,
SemIR::Branch inst) -> void {
// Opportunistically avoid creating a BasicBlock that contains just a branch.
// TODO: Don't do this if it would remove a loop preheader block.
llvm::BasicBlock* block = context.builder().GetInsertBlock();
if (block->empty() && context.TryToReuseBlock(inst.target_id, block)) {
// Reuse this block as the branch target.
} else {
context.builder().CreateBr(context.GetBlock(inst.target_id));
}
context.builder().ClearInsertionPoint();
}
auto HandleBranchIf(FunctionContext& context, SemIR::InstId /*inst_id*/,
SemIR::BranchIf inst) -> void {
llvm::Value* cond = context.GetLocal(inst.cond_id);
llvm::BasicBlock* then_block = context.GetBlock(inst.target_id);
llvm::BasicBlock* else_block = context.CreateSyntheticBlock();
context.builder().CreateCondBr(cond, then_block, else_block);
context.builder().SetInsertPoint(else_block);
}
auto HandleBranchWithArg(FunctionContext& context, SemIR::InstId /*inst_id*/,
SemIR::BranchWithArg inst) -> void {
llvm::Value* arg = context.GetLocal(inst.arg_id);
SemIR::TypeId arg_type_id =
context.sem_ir().insts().Get(inst.arg_id).type_id();
// Opportunistically avoid creating a BasicBlock that contains just a branch.
// We only do this for a block that we know will only have a single
// predecessor, so that we can correctly populate the predecessors of the
// PHINode.
llvm::BasicBlock* block = context.builder().GetInsertBlock();
llvm::BasicBlock* phi_predecessor = block;
if (block->empty() && context.IsCurrentSyntheticBlock(block) &&
context.TryToReuseBlock(inst.target_id, block)) {
// Reuse this block as the branch target.
phi_predecessor = block->getSinglePredecessor();
CARBON_CHECK(phi_predecessor)
<< "Synthetic block did not have a single predecessor";
} else {
context.builder().CreateBr(context.GetBlock(inst.target_id));
}
context.GetBlockArg(inst.target_id, arg_type_id)
->addIncoming(arg, phi_predecessor);
context.builder().ClearInsertionPoint();
}
auto HandleBuiltin(FunctionContext& /*context*/, SemIR::InstId /*inst_id*/,
SemIR::Builtin inst) -> void {
CARBON_FATAL() << "TODO: Add support: " << inst;
}
auto HandleCall(FunctionContext& context, SemIR::InstId inst_id,
SemIR::Call inst) -> void {
auto* callee = llvm::cast<llvm::Function>(context.GetLocal(inst.callee_id));
std::vector<llvm::Value*> args;
llvm::ArrayRef<SemIR::InstId> arg_ids =
context.sem_ir().inst_blocks().Get(inst.args_id);
if (SemIR::GetInitializingRepresentation(context.sem_ir(), inst.type_id)
.has_return_slot()) {
args.push_back(context.GetLocal(arg_ids.back()));
arg_ids = arg_ids.drop_back();
}
for (auto arg_id : arg_ids) {
auto arg_type_id = context.sem_ir().insts().Get(arg_id).type_id();
if (SemIR::GetValueRepresentation(context.sem_ir(), arg_type_id).kind !=
SemIR::ValueRepresentation::None) {
args.push_back(context.GetLocal(arg_id));
}
}
auto* call = context.builder().CreateCall(callee, args);
context.SetLocal(inst_id, call);
// Name the call's result the same as the callee.
// TODO: Is this a helpful name?
if (!call->getType()->isVoidTy()) {
call->setName(callee->getName());
}
}
auto HandleClassDeclaration(FunctionContext& /*context*/,
SemIR::InstId /*inst_id*/,
SemIR::ClassDeclaration /*inst*/) -> void {
// No action to perform.
}
// Extracts an element of an aggregate, such as a struct, tuple, or class, by
// index. Depending on the expression category and value representation of the
// aggregate input, this will either produce a value or a reference.
static auto GetAggregateElement(FunctionContext& context,
SemIR::InstId aggr_inst_id,
SemIR::MemberIndex idx,
SemIR::TypeId result_type_id, llvm::Twine name)
-> llvm::Value* {
auto aggr_inst = context.sem_ir().insts().Get(aggr_inst_id);
auto* aggr_value = context.GetLocal(aggr_inst_id);
switch (SemIR::GetExpressionCategory(context.sem_ir(), aggr_inst_id)) {
case SemIR::ExpressionCategory::Error:
case SemIR::ExpressionCategory::NotExpression:
case SemIR::ExpressionCategory::Initializing:
case SemIR::ExpressionCategory::Mixed:
CARBON_FATAL() << "Unexpected expression category for aggregate access";
case SemIR::ExpressionCategory::Value: {
auto value_rep =
SemIR::GetValueRepresentation(context.sem_ir(), aggr_inst.type_id());
CARBON_CHECK(value_rep.aggregate_kind !=
SemIR::ValueRepresentation::NotAggregate)
<< "aggregate type should have aggregate value representation";
switch (value_rep.kind) {
case SemIR::ValueRepresentation::Unknown:
CARBON_FATAL() << "Lowering access to incomplete aggregate type";
case SemIR::ValueRepresentation::None:
return aggr_value;
case SemIR::ValueRepresentation::Copy:
// We are holding the values of the aggregate directly, elementwise.
return context.builder().CreateExtractValue(aggr_value, idx.index,
name);
case SemIR::ValueRepresentation::Pointer: {
// The value representation is a pointer to an aggregate that we want
// to index into.
auto pointee_type_id =
context.sem_ir().GetPointeeType(value_rep.type_id);
auto* value_type = context.GetType(pointee_type_id);
auto* elem_ptr = context.builder().CreateStructGEP(
value_type, aggr_value, idx.index, name);
if (!value_rep.elements_are_values()) {
// `elem_ptr` points to an object representation, which is our
// result.
return elem_ptr;
}
// `elem_ptr` points to a value representation. Load it.
auto result_value_type_id =
SemIR::GetValueRepresentation(context.sem_ir(), result_type_id)
.type_id;
return context.builder().CreateLoad(
context.GetType(result_value_type_id), elem_ptr, name + ".load");
}
case SemIR::ValueRepresentation::Custom:
CARBON_FATAL()
<< "Aggregate should never have custom value representation";
}
}
case SemIR::ExpressionCategory::DurableReference:
case SemIR::ExpressionCategory::EphemeralReference: {
// Just locate the aggregate element.
auto* aggr_type = context.GetType(aggr_inst.type_id());
return context.builder().CreateStructGEP(aggr_type, aggr_value, idx.index,
name);
}
}
}
static auto GetStructFieldName(FunctionContext& context,
SemIR::TypeId struct_type_id,
SemIR::MemberIndex index) -> llvm::StringRef {
auto fields = context.sem_ir().inst_blocks().Get(
context.sem_ir()
.insts()
.GetAs<SemIR::StructType>(
context.sem_ir().types().Get(struct_type_id).inst_id)
.fields_id);
auto field = context.sem_ir().insts().GetAs<SemIR::StructTypeField>(
fields[index.index]);
return context.sem_ir().identifiers().Get(field.name_id);
}
auto HandleClassFieldAccess(FunctionContext& context, SemIR::InstId inst_id,
SemIR::ClassFieldAccess inst) -> void {
// Find the class that we're performing access into.
auto class_type_id = context.sem_ir().insts().Get(inst.base_id).type_id();
auto class_id =
context.sem_ir()
.insts()
.GetAs<SemIR::ClassType>(
context.sem_ir().GetTypeAllowBuiltinTypes(class_type_id))
.class_id;
auto& class_info = context.sem_ir().classes().Get(class_id);
// Translate the class field access into a struct access on the object
// representation.
context.SetLocal(
inst_id,
GetAggregateElement(
context, inst.base_id, inst.index, inst.type_id,
GetStructFieldName(context, class_info.object_representation_id,
inst.index)));
}
auto HandleDereference(FunctionContext& context, SemIR::InstId inst_id,
SemIR::Dereference inst) -> void {
context.SetLocal(inst_id, context.GetLocal(inst.pointer_id));
}
auto HandleField(FunctionContext& /*context*/, SemIR::InstId /*inst_id*/,
SemIR::Field /*inst*/) -> void {
// No action to perform.
}
auto HandleFunctionDeclaration(FunctionContext& /*context*/,
SemIR::InstId /*inst_id*/,
SemIR::FunctionDeclaration inst) -> void {
CARBON_FATAL()
<< "Should not be encountered. If that changes, we may want to change "
"higher-level logic to skip them rather than calling this. "
<< inst;
}
auto HandleInitializeFrom(FunctionContext& context, SemIR::InstId /*inst_id*/,
SemIR::InitializeFrom inst) -> void {
auto storage_type_id = context.sem_ir().insts().Get(inst.dest_id).type_id();
context.FinishInitialization(storage_type_id, inst.dest_id, inst.src_id);
}
auto HandleIntegerLiteral(FunctionContext& context, SemIR::InstId inst_id,
SemIR::IntegerLiteral inst) -> void {
const llvm::APInt& i = context.sem_ir().integers().Get(inst.integer_id);
// TODO: This won't offer correct semantics, but seems close enough for now.
llvm::Value* v =
llvm::ConstantInt::get(context.builder().getInt32Ty(), i.getZExtValue());
context.SetLocal(inst_id, v);
}
auto HandleNameReference(FunctionContext& context, SemIR::InstId inst_id,
SemIR::NameReference inst) -> void {
auto type_inst_id = context.sem_ir().GetTypeAllowBuiltinTypes(inst.type_id);
if (type_inst_id == SemIR::InstId::BuiltinNamespaceType) {
return;
}
context.SetLocal(inst_id, context.GetLocalOrGlobal(inst.value_id));
}
auto HandleNamespace(FunctionContext& /*context*/, SemIR::InstId /*inst_id*/,
SemIR::Namespace inst) -> void {
CARBON_FATAL()
<< "Should not be encountered. If that changes, we may want to change "
"higher-level logic to skip them rather than calling this. "
<< inst;
}
auto HandleNoOp(FunctionContext& /*context*/, SemIR::InstId /*inst_id*/,
SemIR::NoOp /*inst*/) -> void {
// No action to take.
}
auto HandleParameter(FunctionContext& /*context*/, SemIR::InstId /*inst_id*/,
SemIR::Parameter /*inst*/) -> void {
CARBON_FATAL() << "Parameters should be lowered by `BuildFunctionDefinition`";
}
auto HandleRealLiteral(FunctionContext& context, SemIR::InstId inst_id,
SemIR::RealLiteral inst) -> void {
const Real& real = context.sem_ir().reals().Get(inst.real_id);
// TODO: This will probably have overflow issues, and should be fixed.
double val =
real.mantissa.getZExtValue() *
std::pow((real.is_decimal ? 10 : 2), real.exponent.getSExtValue());
llvm::APFloat llvm_val(val);
context.SetLocal(inst_id, llvm::ConstantFP::get(
context.builder().getDoubleTy(), llvm_val));
}
auto HandleReturn(FunctionContext& context, SemIR::InstId /*inst_id*/,
SemIR::Return /*inst*/) -> void {
context.builder().CreateRetVoid();
}
auto HandleReturnExpression(FunctionContext& context, SemIR::InstId /*inst_id*/,
SemIR::ReturnExpression inst) -> void {
switch (SemIR::GetInitializingRepresentation(
context.sem_ir(),
context.sem_ir().insts().Get(inst.expr_id).type_id())
.kind) {
case SemIR::InitializingRepresentation::None:
case SemIR::InitializingRepresentation::InPlace:
// Nothing to return.
context.builder().CreateRetVoid();
return;
case SemIR::InitializingRepresentation::ByCopy:
// The expression produces the value representation for the type.
context.builder().CreateRet(context.GetLocal(inst.expr_id));
return;
}
}
auto HandleSelfParameter(FunctionContext& /*context*/,
SemIR::InstId /*inst_id*/,
SemIR::SelfParameter /*inst*/) -> void {
CARBON_FATAL() << "Parameters should be lowered by `BuildFunctionDefinition`";
}
auto HandleSpliceBlock(FunctionContext& context, SemIR::InstId inst_id,
SemIR::SpliceBlock inst) -> void {
context.LowerBlock(inst.block_id);
context.SetLocal(inst_id, context.GetLocal(inst.result_id));
}
auto HandleStringLiteral(FunctionContext& /*context*/,
SemIR::InstId /*inst_id*/, SemIR::StringLiteral inst)
-> void {
CARBON_FATAL() << "TODO: Add support: " << inst;
}
auto HandleStructAccess(FunctionContext& context, SemIR::InstId inst_id,
SemIR::StructAccess inst) -> void {
auto struct_type_id = context.sem_ir().insts().Get(inst.struct_id).type_id();
context.SetLocal(
inst_id, GetAggregateElement(
context, inst.struct_id, inst.index, inst.type_id,
GetStructFieldName(context, struct_type_id, inst.index)));
}
auto HandleStructLiteral(FunctionContext& /*context*/,
SemIR::InstId /*inst_id*/,
SemIR::StructLiteral /*inst*/) -> void {
// A StructLiteral should always be converted to a StructInit or StructValue
// if its value is needed.
}
// Emits the value representation for a struct or tuple whose elements are the
// contents of `refs_id`.
auto EmitStructOrTupleValueRepresentation(FunctionContext& context,
SemIR::TypeId type_id,
SemIR::InstBlockId refs_id,
llvm::Twine name) -> llvm::Value* {
auto value_rep = SemIR::GetValueRepresentation(context.sem_ir(), type_id);
switch (value_rep.kind) {
case SemIR::ValueRepresentation::Unknown:
CARBON_FATAL() << "Incomplete aggregate type in lowering";
case SemIR::ValueRepresentation::None:
// TODO: Add a helper to get a "no value representation" value.
return llvm::PoisonValue::get(context.GetType(value_rep.type_id));
case SemIR::ValueRepresentation::Copy: {
auto refs = context.sem_ir().inst_blocks().Get(refs_id);
CARBON_CHECK(refs.size() == 1)
<< "Unexpected size for aggregate with by-copy value representation";
// TODO: Remove the LLVM StructType wrapper in this case, so we don't
// need this `insert_value` wrapping.
return context.builder().CreateInsertValue(
llvm::PoisonValue::get(context.GetType(value_rep.type_id)),
context.GetLocal(refs[0]), {0});
}
case SemIR::ValueRepresentation::Pointer: {
auto pointee_type_id = context.sem_ir().GetPointeeType(value_rep.type_id);
auto* llvm_value_rep_type = context.GetType(pointee_type_id);
// Write the value representation to a local alloca so we can produce a
// pointer to it as the value representation of the struct or tuple.
auto* alloca =
context.builder().CreateAlloca(llvm_value_rep_type,
/*ArraySize=*/nullptr, name);
for (auto [i, ref] :
llvm::enumerate(context.sem_ir().inst_blocks().Get(refs_id))) {
context.builder().CreateStore(
context.GetLocal(ref),
context.builder().CreateStructGEP(llvm_value_rep_type, alloca, i));
}
return alloca;
}
case SemIR::ValueRepresentation::Custom:
CARBON_FATAL()
<< "Aggregate should never have custom value representation";
}
}
auto HandleStructInit(FunctionContext& context, SemIR::InstId inst_id,
SemIR::StructInit inst) -> void {
auto* llvm_type = context.GetType(inst.type_id);
switch (SemIR::GetInitializingRepresentation(context.sem_ir(), inst.type_id)
.kind) {
case SemIR::InitializingRepresentation::None:
case SemIR::InitializingRepresentation::InPlace:
// TODO: Add a helper to poison a value slot.
context.SetLocal(inst_id, llvm::PoisonValue::get(llvm_type));
break;
case SemIR::InitializingRepresentation::ByCopy: {
context.SetLocal(
inst_id, EmitStructOrTupleValueRepresentation(
context, inst.type_id, inst.elements_id, "struct.init"));
break;
}
}
}
auto HandleStructValue(FunctionContext& context, SemIR::InstId inst_id,
SemIR::StructValue inst) -> void {
context.SetLocal(inst_id,
EmitStructOrTupleValueRepresentation(
context, inst.type_id, inst.elements_id, "struct"));
}
auto HandleStructTypeField(FunctionContext& /*context*/,
SemIR::InstId /*inst_id*/,
SemIR::StructTypeField /*inst*/) -> void {
// No action to take.
}
auto HandleTupleAccess(FunctionContext& context, SemIR::InstId inst_id,
SemIR::TupleAccess inst) -> void {
context.SetLocal(inst_id,
GetAggregateElement(context, inst.tuple_id, inst.index,
inst.type_id, "tuple.elem"));
}
auto HandleTupleIndex(FunctionContext& context, SemIR::InstId inst_id,
SemIR::TupleIndex inst) -> void {
auto index_inst =
context.sem_ir().insts().GetAs<SemIR::IntegerLiteral>(inst.index_id);
auto index =
context.sem_ir().integers().Get(index_inst.integer_id).getZExtValue();
context.SetLocal(inst_id, GetAggregateElement(context, inst.tuple_id,
SemIR::MemberIndex(index),
inst.type_id, "tuple.index"));
}
auto HandleTupleLiteral(FunctionContext& /*context*/, SemIR::InstId /*inst_id*/,
SemIR::TupleLiteral /*inst*/) -> void {
// A TupleLiteral should always be converted to a TupleInit or TupleValue if
// its value is needed.
}
auto HandleTupleInit(FunctionContext& context, SemIR::InstId inst_id,
SemIR::TupleInit inst) -> void {
auto* llvm_type = context.GetType(inst.type_id);
switch (SemIR::GetInitializingRepresentation(context.sem_ir(), inst.type_id)
.kind) {
case SemIR::InitializingRepresentation::None:
case SemIR::InitializingRepresentation::InPlace:
// TODO: Add a helper to poison a value slot.
context.SetLocal(inst_id, llvm::PoisonValue::get(llvm_type));
break;
case SemIR::InitializingRepresentation::ByCopy: {
context.SetLocal(
inst_id, EmitStructOrTupleValueRepresentation(
context, inst.type_id, inst.elements_id, "tuple.init"));
break;
}
}
}
auto HandleTupleValue(FunctionContext& context, SemIR::InstId inst_id,
SemIR::TupleValue inst) -> void {
context.SetLocal(
inst_id, EmitStructOrTupleValueRepresentation(context, inst.type_id,
inst.elements_id, "tuple"));
}
auto HandleUnaryOperatorNot(FunctionContext& context, SemIR::InstId inst_id,
SemIR::UnaryOperatorNot inst) -> void {
context.SetLocal(
inst_id, context.builder().CreateNot(context.GetLocal(inst.operand_id)));
}
auto HandleVarStorage(FunctionContext& context, SemIR::InstId inst_id,
SemIR::VarStorage inst) -> void {
// TODO: Eventually this name will be optional, and we'll want to provide
// something like `var` as a default. However, that's not possible right now
// so cannot be tested.
auto name = context.sem_ir().identifiers().Get(inst.name_id);
auto* alloca = context.builder().CreateAlloca(context.GetType(inst.type_id),
/*ArraySize=*/nullptr, name);
context.SetLocal(inst_id, alloca);
}
} // namespace Carbon::Lower