carbon-language/carbon-lang
1
0
Fork 0
mirror of https://github.com/carbon-language/carbon-lang.git synced 2026-09-24 19:50:14 +01:00
Code Issues Packages Projects Releases 10 Wiki Activity
Files
5c544f7c2fa7b25bdfb845c49f26344205e41bcb
carbon-lang/toolchain/lower/file_context.cpp
T
Richard Smith 5c544f7c2f Give thunks weak_odr linkage. (#7525) 
We can end up emitting the same thunk from multiple compilations in some
cases -- in particular, when the thunk is wrapping a function that is
either synthesized by the compiler or imported from C++. When this
happens, we will have multiple-definition link errors unless we allow
redefinitions across multiple files.

It'd be nice to detect when we need to do this and when we don't, but
that's a bit tricky to do in practice. Ideally, in fact, we would use a
different strategy, and emit the thunks as discardable definitions in
each compilation that *uses* them. But for now emitting them with
weak_odr linkage seems like a good way to make progress.
2026-07-17 13:25:19 +00:00

839 lines
34 KiB
C++
Raw Blame History

// 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 "toolchain/lower/file_context.h"
#include <memory>
#include <optional>
#include <string>
#include <utility>
#include "clang/AST/BaseSubobject.h"
#include "clang/CodeGen/ModuleBuilder.h"
#include "common/check.h"
#include "common/pretty_stack_trace_function.h"
#include "common/vlog.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Sequence.h"
#include "llvm/Linker/Linker.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
#include "toolchain/base/kind_switch.h"
#include "toolchain/lower/clang_global_decl.h"
#include "toolchain/lower/constant.h"
#include "toolchain/lower/function_context.h"
#include "toolchain/lower/options.h"
#include "toolchain/lower/specific_coalescer.h"
#include "toolchain/sem_ir/absolute_node_ref.h"
#include "toolchain/sem_ir/diagnostic_loc_converter.h"
#include "toolchain/sem_ir/entry_point.h"
#include "toolchain/sem_ir/expr_info.h"
#include "toolchain/sem_ir/file.h"
#include "toolchain/sem_ir/function.h"
#include "toolchain/sem_ir/generic.h"
#include "toolchain/sem_ir/ids.h"
#include "toolchain/sem_ir/inst.h"
#include "toolchain/sem_ir/inst_categories.h"
#include "toolchain/sem_ir/inst_kind.h"
#include "toolchain/sem_ir/mangler.h"
#include "toolchain/sem_ir/pattern.h"
#include "toolchain/sem_ir/stringify.h"
#include "toolchain/sem_ir/type_info.h"
#include "toolchain/sem_ir/typed_insts.h"
namespace Carbon::Lower {
FileContext::FileContext(Context& context, const SemIR::File& sem_ir,
const SemIR::InstNamer* inst_namer,
llvm::raw_ostream* vlog_stream)
: context_(&context),
sem_ir_(&sem_ir),
inst_namer_(inst_namer),
vlog_stream_(vlog_stream),
functions_(LoweredFunctionStore::MakeForOverwrite(sem_ir.functions())),
specific_functions_(sem_ir.specifics(), std::nullopt),
types_(LoweredTypeStore::MakeWithExplicitSize(
sem_ir.constant_values().ConcreteStoreSize(),
sem_ir.constant_values().GetTypeIdTag(), {nullptr, nullptr})),
constants_(LoweredConstantStore::MakeWithExplicitSize(
sem_ir.insts().size(), sem_ir.insts().GetIdTag(), nullptr)),
lowered_specifics_(sem_ir.generics(),
llvm::SmallVector<SemIR::SpecificId>()),
coalescer_(vlog_stream_, sem_ir.specifics()),
vtables_(decltype(vtables_)::MakeForOverwrite(sem_ir.vtables())),
specific_vtables_(sem_ir.specifics(), nullptr) {
// Initialization that relies on invariants of the class.
cpp_code_generator_ = cpp_file() ? cpp_file()->GetCodeGenerator() : nullptr;
CARBON_CHECK(
!cpp_code_generator_ ||
(&cpp_code_generator_->GetModule()->getContext() == &llvm_context()));
CARBON_CHECK(!sem_ir.has_errors(),
"Generating LLVM IR from invalid SemIR::File is unsupported.");
}
// TODO: Move this to lower.cpp.
auto FileContext::PrepareToLower() -> void {
// Lower all types that were required to be complete.
for (auto type_id : sem_ir_->types().complete_types()) {
if (type_id.index >= 0) {
types_.Set(type_id,
BuildType(*this, sem_ir_->types().GetTypeInstId(type_id)));
}
}
// Lower function declarations.
for (auto [id, function] : sem_ir_->functions().enumerate()) {
if (id == sem_ir().global_ctor_id()) {
// The global constructor is only lowered when we generate its definition.
// LLVM doesn't allow an internal linkage function to be undefined.
continue;
}
if (function.evaluation_mode == SemIR::Function::EvaluationMode::MustEval) {
// musteval functions are never lowered.
continue;
}
functions_.Set(id, BuildFunctionDecl(id));
}
// TODO: Split vtable declaration creation from definition creation to avoid
// redundant vtable definitions for imported vtables.
for (const auto& [id, vtable] : sem_ir_->vtables().enumerate()) {
const auto& class_info = sem_ir().classes().Get(vtable.class_id);
// Vtables can't be generated for generics, only for their specifics - and
// must be done lazily based on the use of those specifics.
if (!class_info.generic_id.has_value()) {
vtables_.Set(id, BuildVtable(vtable, SemIR::SpecificId::None));
}
}
// Lower constants.
LowerConstants(*this, constants_);
}
// TODO: Move this to lower.cpp.
auto FileContext::LowerDefinitions() -> void {
// Lower global variable definitions.
// TODO: Storing both a `constants_` array and a separate `global_variables_`
// map is redundant.
LowerGlobalVariables(sem_ir().top_inst_block_id());
// Lower static class variable definitions.
for (auto class_info : sem_ir().classes().values()) {
auto inst_block_id = class_info.body_block_id;
if (inst_block_id.has_value()) {
LowerGlobalVariables(inst_block_id);
}
}
// Lower function definitions.
for (auto [id, fn_info] : sem_ir_->functions().enumerate()) {
// If we created a declaration and the function definition is not imported,
// build a definition.
if (functions_.Get(id) && fn_info.definition_id.has_value() &&
!sem_ir().insts().GetImportSource(fn_info.definition_id).has_value()) {
BuildFunctionDefinition(id);
}
}
// Append `__global_init` to `llvm::global_ctors` to initialize global
// variables.
if (auto global_ctor_id = sem_ir().global_ctor_id();
global_ctor_id.has_value()) {
// This is basically an inlined and specialized version of
// `BuildFunctionDecl` because global_ctor is a bit special (it has no
// declarations, for one thing).
// TODO: Consider making the global ctor not a function at all, but a
// special block.
auto function_type_info = BuildFunctionTypeInfo(
{{this, global_ctor_id, SemIR::SpecificId::None}});
std::string mangled_name = "_C__global_init.";
auto package_id = sem_ir().package_id();
if (auto ident_id = package_id.AsIdentifierId(); ident_id.has_value()) {
mangled_name += sem_ir().identifiers().Get(ident_id);
} else {
mangled_name += package_id.AsSpecialName();
}
auto* llvm_function = llvm_module().getFunction(mangled_name);
if (!llvm_function) {
llvm_function = llvm::Function::Create(function_type_info.type,
llvm::Function::InternalLinkage,
mangled_name, llvm_module());
CARBON_CHECK(llvm_function->getName() == mangled_name,
"Mangled name collision: {0}", mangled_name);
}
FunctionInfo function_info = {
.type = function_type_info.type,
.di_type = function_type_info.di_type,
.lowered_param_indices =
std::move(function_type_info.lowered_param_indices),
.unused_param_indices =
std::move(function_type_info.unused_param_indices),
.llvm_function = llvm_function,
.inexact = function_type_info.inexact};
functions_.Set(global_ctor_id, function_info);
const auto& global_ctor = sem_ir().functions().Get(global_ctor_id);
BuildFunctionBody(global_ctor_id, SemIR::SpecificId::None, global_ctor,
*this, global_ctor);
llvm::appendToGlobalCtors(llvm_module(), llvm_function,
/*Priority=*/0);
}
}
auto FileContext::Finalize() -> void {
if (cpp_code_generator_) {
// Clang code generation should not actually modify the AST, but isn't
// const-correct.
cpp_code_generator_->HandleTranslationUnit(
const_cast<clang::ASTContext&>(cpp_file()->ast_context()));
}
// Find equivalent specifics (from the same generic), replace all uses and
// remove duplicately lowered function definitions.
coalescer_.CoalesceEquivalentSpecifics(lowered_specifics_,
specific_functions_);
}
auto FileContext::GetConstant(SemIR::ConstantId const_id,
SemIR::InstId use_inst_id) -> llvm::Value* {
auto const_inst_id = sem_ir().constant_values().GetInstId(const_id);
auto* const_value = constants_.Get(const_inst_id);
// For value expressions and initializing expressions, the value produced by
// a constant instruction is a value representation of the constant. For
// initializing expressions, `FinishInit` will perform a copy if needed.
switch (auto cat = SemIR::GetExprCategory(sem_ir(), const_inst_id)) {
case SemIR::ExprCategory::Value:
case SemIR::ExprCategory::ReprInitializing:
case SemIR::ExprCategory::InPlaceInitializing:
break;
case SemIR::ExprCategory::DurableRef:
case SemIR::ExprCategory::EphemeralRef:
// Constant reference expressions lower to an address.
return const_value;
case SemIR::ExprCategory::NotExpr:
case SemIR::ExprCategory::Error:
case SemIR::ExprCategory::Pattern:
case SemIR::ExprCategory::Mixed:
case SemIR::ExprCategory::RefTagged:
case SemIR::ExprCategory::Dependent:
CARBON_FATAL("Unexpected category {0} for lowered constant {1}", cat,
sem_ir().insts().Get(const_inst_id));
};
auto value_rep = SemIR::ValueRepr::ForType(
sem_ir(), sem_ir().insts().Get(const_inst_id).type_id());
if (value_rep.kind != SemIR::ValueRepr::Pointer) {
return const_value;
}
// The value representation is a pointer. Generate a variable to hold the
// value, or find and reuse an existing one.
if (auto result = global_variables().Lookup(const_inst_id)) {
return result.value();
}
// Include both the name of the constant, if any, and the point of use in
// the name of the variable.
llvm::StringRef const_name;
llvm::StringRef use_name;
if (inst_namer_) {
const_name = inst_namer_->GetUnscopedNameFor(const_inst_id);
if (use_inst_id.has_value()) {
use_name = inst_namer_->GetUnscopedNameFor(use_inst_id);
}
}
// We always need to give the global a name even if the instruction namer
// doesn't have one to use.
if (const_name.empty()) {
const_name = "const";
}
if (use_name.empty()) {
use_name = "anon";
}
llvm::StringRef sep = (use_name[0] == '.') ? "" : ".";
auto* global_variable = new llvm::GlobalVariable(
llvm_module(), GetType(sem_ir().GetPointeeType(value_rep.type_id)),
/*isConstant=*/true, llvm::GlobalVariable::InternalLinkage, const_value,
const_name + sep + use_name);
global_variables_.Insert(const_inst_id, global_variable);
return global_variable;
}
auto FileContext::GetOrCreateFunctionInfo(
SemIR::FunctionId function_id, SemIR::SpecificId specific_id,
FileContext* fallback_file, SemIR::FunctionId fallback_function_id,
SemIR::SpecificId fallback_specific_id) -> std::optional<FunctionInfo>& {
// If we have already lowered a declaration of this function, just return it.
// TODO: If the existing declaration is inexact, and we now have a fallback,
// we should try again.
auto& result = GetFunctionInfo(function_id, specific_id);
if (!result) {
result = BuildFunctionDecl(function_id, specific_id, fallback_file,
fallback_function_id, fallback_specific_id);
}
return result;
}
auto FileContext::LowerGlobalVariables(SemIR::InstBlockId inst_block_id)
-> void {
for (auto inst_id : sem_ir().inst_blocks().Get(inst_block_id)) {
// Only `VarStorage` indicates a global variable declaration in the
// top instruction block.
if (auto var = sem_ir().insts().TryGetAs<SemIR::VarStorage>(inst_id)) {
// Get the global variable declaration. We created this when lowering the
// constant unless the variable is unnamed, in which case we need to
// create it now.
llvm::GlobalVariable* llvm_var = nullptr;
if (auto const_id = sem_ir().constant_values().Get(inst_id);
const_id.is_constant()) {
llvm_var = cast<llvm::GlobalVariable>(GetConstant(const_id, inst_id));
} else {
// We should never be emitting a definition for a C++ global variable.
llvm_var = BuildNonCppGlobalVariableDecl(*var);
}
// Convert the declaration of this variable into a definition by adding an
// initializer.
global_variables_.Insert(inst_id, llvm_var);
llvm_var->setInitializer(
llvm::Constant::getNullValue(llvm_var->getValueType()));
}
}
}
auto FileContext::HandleReferencedCppFunction(clang::FunctionDecl* cpp_decl)
-> llvm::Function* {
// Create the LLVM function (`CodeGenModule::GetOrCreateLLVMFunction()`)
// so that code generation (`CodeGenModule::EmitGlobal()`) would see this
// function name (`CodeGenModule::getMangledName()`), and will generate
// its definition.
auto* function_address = dyn_cast<llvm::Function>(
cpp_code_generator_->GetAddrOfGlobal(CreateGlobalDecl(cpp_decl),
/*isForDefinition=*/false));
CARBON_CHECK(function_address);
return function_address;
}
auto FileContext::HandleReferencedSpecificFunction(
SemIR::FunctionId function_id, SemIR::SpecificId specific_id,
llvm::Type* llvm_type) -> void {
CARBON_CHECK(specific_id.has_value());
// Add this specific function to a list of specific functions whose
// definitions we need to emit.
// TODO: Don't do this if we know this function is emitted as a
// non-discardable symbol in the IR for some other file.
context().AddPendingSpecificFunctionDefinition({.context = this,
.function_id = function_id,
.specific_id = specific_id});
// Create a unique fingerprint for the function type.
// For now, we compute the function type fingerprint only for specifics,
// though we might need it for all functions in order to create a canonical
// fingerprint across translation units.
coalescer_.CreateTypeFingerprint(specific_id, llvm_type);
}
auto FileContext::GetOrCreateLLVMFunction(
const FunctionTypeInfo& function_type_info, SemIR::FunctionId function_id,
SemIR::SpecificId specific_id) -> llvm::Function* {
const auto& function = sem_ir().functions().Get(function_id);
// If this is a C++ function, tell Clang that we referenced it.
// The global_ctor function can't be a C++ function (but doesn't have any
// decl_id so it doesn't fall out naturally from the handling below)
if (function_id != sem_ir().global_ctor_id()) {
if (const auto* clang_decl =
sem_ir().clang_decls().Lookup(function.first_decl_id())) {
if (clang_decl->is_imported) {
CARBON_CHECK(!specific_id.has_value(),
"Specific functions cannot have C++ definitions");
return HandleReferencedCppFunction(clang_decl->decl()->getAsFunction());
}
}
}
SemIR::Mangler m(sem_ir(), context().total_ir_count(),
context().mangle_string_fingerprint());
std::string mangled_name = m.Mangle(function_id, specific_id);
if (auto* existing = llvm_module().getFunction(mangled_name)) {
// We might have already lowered this function while lowering a different
// file. That's OK.
// TODO: If the prior function was inexact and the new one is not, we should
// lower this new one and replace the existing function with it.
// TODO: Check-fail or maybe diagnose if the two LLVM functions are not
// produced by declarations of the same Carbon function. Name collisions
// between non-private members of the same library should have been
// diagnosed by check if detected, but it's not clear that check will
// always be able to see this problem. In theory, name collisions could
// also occur due to fingerprint collision.
return existing;
}
// If this is a specific function, we may need to do additional work to
// emit its definition.
if (specific_id.has_value()) {
HandleReferencedSpecificFunction(function_id, specific_id,
function_type_info.type);
}
auto* llvm_function = llvm::Function::Create(function_type_info.type,
llvm::Function::ExternalLinkage,
mangled_name, llvm_module());
CARBON_CHECK(llvm_function->getName() == mangled_name,
"Mangled name collision: {0}", mangled_name);
// Set up parameters and the return slot.
for (auto [name_id, arg] : llvm::zip_equal(function_type_info.param_name_ids,
llvm_function->args())) {
arg.setName(sem_ir().names().GetIRBaseName(name_id));
}
if (function_type_info.sret_type != nullptr) {
auto& return_arg = *llvm_function->args().begin();
return_arg.addAttr(llvm::Attribute::getWithStructRetType(
llvm_context(), function_type_info.sret_type));
}
return llvm_function;
}
auto FileContext::BuildFunctionDecl(SemIR::FunctionId function_id,
SemIR::SpecificId specific_id,
FileContext* fallback_file,
SemIR::FunctionId fallback_function_id,
SemIR::SpecificId fallback_specific_id)
-> std::optional<FunctionInfo> {
const auto& function = sem_ir().functions().Get(function_id);
// Don't lower generic functions. Note that associated functions in interfaces
// have `Self` in scope, so are implicitly generic functions.
if (function.generic_id.has_value() && !specific_id.has_value()) {
return std::nullopt;
}
// Don't lower builtins.
if (function.builtin_function_kind() != SemIR::BuiltinFunctionKind::None) {
return std::nullopt;
}
// Don't lower C++ functions that use a thunk. We will never reference them
// directly, and their signatures would not be expected to match the
// corresponding C++ function anyway.
if (function.special_function_kind ==
SemIR::Function::SpecialFunctionKind::HasCppThunk) {
return std::nullopt;
}
// TODO: Consider tracking whether the function has been used, and only
// lowering it if it's needed.
FunctionInContext func_infos[] = {
{this, function_id, specific_id},
{fallback_file, fallback_function_id, fallback_specific_id}};
auto function_type_info =
BuildFunctionTypeInfo(llvm::ArrayRef(func_infos, fallback_file ? 2 : 1));
auto* llvm_function =
GetOrCreateLLVMFunction(function_type_info, function_id, specific_id);
return {{.type = function_type_info.type,
.di_type = function_type_info.di_type,
.lowered_param_indices =
std::move(function_type_info.lowered_param_indices),
.unused_param_indices =
std::move(function_type_info.unused_param_indices),
.llvm_function = llvm_function,
.inexact = function_type_info.inexact}};
}
// Find the file and function ID describing the definition of a function.
static auto GetFunctionDefinition(const SemIR::File* decl_ir,
SemIR::FunctionId function_id)
-> std::pair<const SemIR::File*, SemIR::FunctionId> {
// Find the file containing the definition.
auto decl_id = decl_ir->functions().Get(function_id).definition_id;
if (!decl_id.has_value()) {
// Function is not defined.
return {nullptr, SemIR::FunctionId::None};
}
// Find the function declaration this function was originally imported from.
while (true) {
auto import_inst_id = decl_ir->insts().GetImportSource(decl_id);
if (!import_inst_id.has_value()) {
break;
}
auto import_inst = decl_ir->import_ir_insts().Get(import_inst_id);
decl_ir = decl_ir->import_irs().Get(import_inst.ir_id()).sem_ir;
decl_id = import_inst.inst_id();
}
auto decl_ir_function_id =
decl_ir->insts().GetAs<SemIR::FunctionDecl>(decl_id).function_id;
return {decl_ir, decl_ir_function_id};
}
auto FileContext::BuildFunctionDefinition(SemIR::FunctionId function_id,
SemIR::SpecificId specific_id)
-> void {
auto [definition_ir, definition_ir_function_id] =
GetFunctionDefinition(&sem_ir(), function_id);
if (!definition_ir) {
// Function is probably defined in another file; not an error.
return;
}
const auto& definition_function =
definition_ir->functions().Get(definition_ir_function_id);
BuildFunctionBody(
function_id, specific_id, sem_ir().functions().Get(function_id),
context().GetFileContext(definition_ir), definition_function);
}
auto FileContext::BuildFunctionBody(SemIR::FunctionId function_id,
SemIR::SpecificId specific_id,
const SemIR::Function& declaration_function,
FileContext& definition_context,
const SemIR::Function& definition_function)
-> void {
// On crash, report the function we were lowering.
PrettyStackTraceFunction stack_trace_entry([&](llvm::raw_ostream& output) {
SemIR::DiagnosticLocConverter converter(
&context().tree_and_subtrees_getters(), &sem_ir());
auto converted =
converter.Convert(SemIR::LocId(declaration_function.definition_id),
/*token_only=*/false);
converted.loc.FormatLocation(output);
output << "Lowering function ";
if (specific_id.has_value()) {
output << SemIR::StringifySpecific(sem_ir(), specific_id);
} else {
output << SemIR::StringifyConstantInst(
sem_ir(), declaration_function.definition_id);
}
output << "\n";
// Crash output has a tab indent; try to indent slightly past that.
converted.loc.FormatSnippet(output, /*indent=*/10);
});
// Note that `definition_function` is potentially from a different SemIR::File
// than the one that this file context represents. Any lowering done for
// values derived from `definition_function` should use `definition_context`
// instead of our context.
const auto& definition_ir = definition_context.sem_ir();
auto function_info = GetFunctionInfo(function_id, specific_id);
CARBON_CHECK(function_info && function_info->llvm_function,
"Attempting to define function that was not declared");
CARBON_CHECK(!function_info->inexact,
"Attempting to emit definition of inexact function: {0}",
*function_info->llvm_function);
const auto& body_block_ids = definition_function.body_block_ids;
CARBON_DCHECK(!body_block_ids.empty(),
"No function body blocks found during lowering.");
// Store which specifics were already lowered (with definitions) for each
// generic.
if (declaration_function.generic_id.has_value() && specific_id.has_value()) {
// TODO: We should track this in the definition context instead so that we
// can deduplicate specifics from different files.
AddLoweredSpecificForGeneric(declaration_function.generic_id, specific_id);
}
// Set the linkage for the definition.
auto linkage = llvm::Function::ExternalLinkage;
if (function_id == sem_ir().global_ctor_id()) {
// The global constructor name would collide with global constructors for
// other files in the same package, so use an internal linkage symbol.
linkage = llvm::Function::InternalLinkage;
} else if (specific_id.has_value()) {
// Specific functions are emitted in each file they are referenced in.
linkage = llvm::Function::LinkOnceODRLinkage;
} else if (declaration_function.special_function_kind ==
SemIR::Function::SpecialFunctionKind::CoreWitness ||
declaration_function.special_function_kind ==
SemIR::Function::SpecialFunctionKind::Thunk) {
// TODO: Emit CoreWitness functions and thunks in files where they're called
// instead of in files where they're defined. That should allow
// LinkOnceODRLinkage.
linkage = llvm::Function::WeakODRLinkage;
}
function_info->llvm_function->setLinkage(linkage);
// Set attributes on the function definition.
{
llvm::AttrBuilder attr_builder(llvm_context());
attr_builder.addAttribute(llvm::Attribute::NoUnwind);
// TODO: We should take the opt level from the SemIR file; it might not be
// the same for all files in a compilation.
if (context().opt_level() == Lower::OptimizationLevel::None) {
// --optimize=none disables all optimizations for this function.
attr_builder.addAttribute(llvm::Attribute::OptimizeNone);
attr_builder.addAttribute(llvm::Attribute::NoInline);
} else {
// Otherwise, always inline thunks.
if (definition_function.special_function_kind ==
SemIR::Function::SpecialFunctionKind::Thunk) {
// TODO: emit the thunk as an alias instead of a separate function,
// when that would be correct.
attr_builder.addAttribute(llvm::Attribute::AlwaysInline);
}
// Convert --optimize=size into optsize and minsize.
if (context().opt_level() == Lower::OptimizationLevel::Size) {
attr_builder.addAttribute(llvm::Attribute::OptimizeForSize);
attr_builder.addAttribute(llvm::Attribute::MinSize);
}
// TODO: Should we generate an InlineHint for some functions? Perhaps for
// those defined in the API file?
}
function_info->llvm_function->addFnAttrs(attr_builder);
}
auto* subprogram = BuildDISubprogram(declaration_function, *function_info);
FunctionContext function_lowering(
definition_context, function_info->llvm_function, *this, function_id,
specific_id, coalescer_.InitializeFingerprintForSpecific(specific_id),
subprogram, vlog_stream_);
auto call_param_ids = definition_ir.inst_blocks().GetOrEmpty(
definition_function.call_params_id);
// Add local variables for the parameters.
for (auto [llvm_index, index] :
llvm::enumerate(function_info->lowered_param_indices)) {
function_lowering.SetLocal(
call_param_ids[index.index],
function_info->llvm_function->getArg(llvm_index));
}
// Add local variables for the SemIR parameters that aren't LLVM parameters.
// These shouldn't actually be used, so they're set to poison values.
for (auto [llvm_index, index] :
llvm::enumerate(function_info->unused_param_indices)) {
auto param_id = call_param_ids[index.index];
function_lowering.SetLocal(
param_id,
llvm::PoisonValue::get(function_lowering.GetTypeOfInst(param_id)));
}
auto decl_block_id = SemIR::InstBlockId::None;
if (function_id == sem_ir().global_ctor_id()) {
decl_block_id = SemIR::InstBlockId::Empty;
} else {
decl_block_id =
definition_ir.insts()
.GetAs<SemIR::FunctionDecl>(definition_function.latest_decl_id())
.decl_block_id;
}
// Lowers the contents of decl_block_id into the corresponding LLVM block,
// creating it if it doesn't already exist.
auto lower_block = [&](SemIR::InstBlockId block_id) {
CARBON_VLOG("Lowering {0}\n", block_id);
auto* llvm_block = function_lowering.GetBlock(block_id);
// Keep the LLVM blocks in lexical order.
llvm_block->moveBefore(function_info->llvm_function->end());
function_lowering.builder().SetInsertPoint(llvm_block);
function_lowering.LowerBlockContents(block_id);
};
CARBON_CHECK(function_lowering.llvm_function().isDeclaration());
lower_block(decl_block_id);
// If the decl block is empty, reuse it as the first body block. We don't do
// this when the decl block is non-empty so that any branches back to the
// first body block don't also re-execute the decl.
llvm::BasicBlock* block = function_lowering.builder().GetInsertBlock();
if (block->empty() &&
function_lowering.TryToReuseBlock(body_block_ids.front(), block)) {
// Reuse this block as the first block of the function body.
} else {
function_lowering.builder().CreateBr(
function_lowering.GetBlock(body_block_ids.front()));
}
// Lower all blocks.
for (auto block_id : body_block_ids) {
lower_block(block_id);
}
// LLVM requires that the entry block has no predecessors.
auto* entry_block = &function_info->llvm_function->getEntryBlock();
if (entry_block->hasNPredecessorsOrMore(1)) {
auto* new_entry_block = llvm::BasicBlock::Create(
llvm_context(), "entry", function_info->llvm_function, entry_block);
llvm::UncondBrInst::Create(entry_block, new_entry_block);
}
// Emit fingerprint accumulated inside the function context.
function_lowering.EmitFinalFingerprint();
context().di_builder().finalizeSubprogram(subprogram);
}
auto FileContext::BuildDISubprogram(const SemIR::Function& function,
const FunctionInfo& function_info)
-> llvm::DISubprogram* {
if (!context().di_compile_unit()) {
return nullptr;
}
auto name = sem_ir().names().GetAsStringIfIdentifier(function.name_id);
CARBON_CHECK(name, "Unexpected special name for function: {0}",
function.name_id);
auto loc = GetLocForDI(function.definition_id);
llvm::DISubroutineType* subroutine_type = function_info.di_type;
auto* subprogram = context().di_builder().createFunction(
context().di_compile_unit(), *name,
function_info.llvm_function->getName(),
/*File=*/context().di_builder().createFile(loc.filename, ""),
/*LineNo=*/loc.line_number, subroutine_type,
/*ScopeLine=*/0, llvm::DINode::FlagZero,
llvm::DISubprogram::SPFlagDefinition);
// Add a variable for each parameter, as that is where DWARF debug information
// comes from.
// TODO: this doesn't declare a variable for the output parameter. Is that
// what we want?
for (auto [argument_number, type] :
llvm::enumerate(llvm::drop_begin(subroutine_type->getTypeArray()))) {
context().di_builder().createParameterVariable(
subprogram, "", argument_number + 1, nullptr, 0, type,
/*AlwaysPreserve=*/true);
}
return subprogram;
}
auto FileContext::BuildGlobalVariableDecl(SemIR::VarStorage var_storage)
-> llvm::Constant* {
// Check if an llvm::GlobalVariable already exists and use it if so.
//
// This happens for C++ variables imported into Carbon. It also
// happens when a Carbon variable is exported and used from C++; code
// generation for the C++ code may have already created an
// llvm::GlobalVariable.
if (const auto* clang_decl =
sem_ir().clang_decls().Lookup(var_storage.pattern_id)) {
auto* constant = cpp_code_generator_->GetAddrOfGlobal(
CreateGlobalDecl(cast<clang::NamedDecl>(clang_decl->decl())),
/*isForDefinition=*/false);
if (constant) {
return constant;
}
}
return BuildNonCppGlobalVariableDecl(var_storage);
}
auto FileContext::BuildNonCppGlobalVariableDecl(SemIR::VarStorage var_storage)
-> llvm::GlobalVariable* {
SemIR::Mangler m(sem_ir(), context().total_ir_count(),
context().mangle_string_fingerprint());
auto mangled_name = m.MangleGlobalVariable(var_storage.pattern_id);
auto linkage = llvm::GlobalVariable::ExternalLinkage;
// If the variable doesn't have an externally-visible name, demote it to
// internal linkage and invent a plausible name that shouldn't collide with
// any of our real manglings.
if (mangled_name.empty()) {
linkage = llvm::GlobalVariable::InternalLinkage;
if (inst_namer_) {
mangled_name =
("var.anon" + inst_namer_->GetUnscopedNameFor(var_storage.pattern_id))
.str();
}
}
auto* type = GetType(var_storage.type_id);
return new llvm::GlobalVariable(llvm_module(), type,
/*isConstant=*/false, linkage,
/*Initializer=*/nullptr, mangled_name);
}
auto FileContext::GetLocForDI(SemIR::InstId inst_id) -> Context::LocForDI {
auto abs_node_ref = GetAbsoluteNodeRef(sem_ir_, SemIR::LocId(inst_id)).back();
return context().GetLocForDI(abs_node_ref);
}
auto FileContext::BuildVtable(const SemIR::Vtable& vtable,
SemIR::SpecificId specific_id)
-> llvm::Constant* {
const auto& class_info = sem_ir().classes().Get(vtable.class_id);
if (!vtable.carbon_native_vtable) {
auto* cxx_record_decl = cast<clang::CXXRecordDecl>(
sem_ir().clang_decls().Lookup(class_info.latest_decl_id())->key.decl);
return cpp_code_generator_->GetAddrOfVTable(
clang::BaseSubobject(cxx_record_decl,
clang::CharUnits::fromQuantity(0)),
cxx_record_decl);
}
SemIR::Mangler m(sem_ir(), context().total_ir_count(),
context().mangle_string_fingerprint());
std::string mangled_name = m.MangleVTable(class_info, specific_id);
if (sem_ir()
.insts()
.GetImportSource(class_info.first_owning_decl_id)
.has_value()) {
// Emit a declaration of an imported vtable using a(n opaque) pointer type.
// This doesn't have to match the definition that appears elsewhere, it'll
// still get merged correctly.
auto* gv = new llvm::GlobalVariable(
llvm_module(),
llvm::PointerType::get(llvm_context(), /*AddressSpace=*/0),
/*isConstant=*/true, llvm::GlobalValue::ExternalLinkage, nullptr,
mangled_name);
gv->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
return gv;
}
auto vtable_inst_block =
sem_ir().inst_blocks().Get(vtable.virtual_functions_id);
auto* entry_type = llvm::IntegerType::getInt32Ty(llvm_context());
auto* table_type = llvm::ArrayType::get(entry_type, vtable_inst_block.size());
auto* llvm_vtable = new llvm::GlobalVariable(
llvm_module(), table_type, /*isConstant=*/true,
llvm::GlobalValue::ExternalLinkage, nullptr, mangled_name);
auto* i32_type = llvm::IntegerType::getInt32Ty(llvm_context());
auto* i64_type = llvm::IntegerType::getInt64Ty(llvm_context());
auto* vtable_const_int =
llvm::ConstantExpr::getPtrToInt(llvm_vtable, i64_type);
llvm::SmallVector<llvm::Constant*> vfuncs;
vfuncs.reserve(vtable_inst_block.size());
for (auto fn_decl_id : vtable_inst_block) {
auto [_1, _2, fn_id, fn_specific_id] =
DecomposeVirtualFunction(sem_ir(), fn_decl_id, specific_id);
vfuncs.push_back(llvm::ConstantExpr::getTrunc(
llvm::ConstantExpr::getSub(
llvm::ConstantExpr::getPtrToInt(
GetOrCreateFunctionInfo(fn_id, fn_specific_id)->llvm_function,
i64_type),
vtable_const_int),
i32_type));
}
llvm_vtable->setInitializer(llvm::ConstantArray::get(table_type, vfuncs));
llvm_vtable->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
return llvm_vtable;
}
} // namespace Carbon::Lower
Reference in New Issue View Git Blame Copy Permalink