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519e633147f2fd541e459cdd4a43391bffc9cf63
carbon-lang/toolchain/lower/file_context.cpp
T
Richard Smith 519e633147 Improve backtrace for lowering crashes. (#5651) 
Factor out the logic for mapping from a `LocId` into a diagnostic
location from check into sem_ir so it can be reused by lowering. Include
the function and instruction being lowered in the pretty stack trace.
Example stack trace:

```carbon
2.      filename: examples/sieve.carbon
3.      core/prelude/types/int.carbon:213:3: lowering function Core.Op(Core.IntLiteral as Core.ImplicitAs(i32))
            fn Op[addr self: Self*](other: Self) = "int.sadd_assign";
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4.      core/prelude/operators/arithmetic.carbon:22:27: lowering call
            fn Op[addr self: Self*](other: Other);
                                    ^~~~~~~~~~~~
```
2025-06-16 23:21:22 +00:00

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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 "toolchain/lower/file_context.h"
#include <memory>
#include <optional>
#include <string>
#include <utility>
#include "clang/CodeGen/ModuleBuilder.h"
#include "common/check.h"
#include "common/vlog.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Sequence.h"
#include "llvm/Linker/Linker.h"
#include "llvm/Support/BLAKE3.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
#include "toolchain/base/kind_switch.h"
#include "toolchain/base/pretty_stack_trace_function.h"
#include "toolchain/lower/constant.h"
#include "toolchain/lower/function_context.h"
#include "toolchain/lower/mangler.h"
#include "toolchain/sem_ir/absolute_node_id.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/pattern.h"
#include "toolchain/sem_ir/stringify.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(), nullptr),
types_(LoweredTypeStore::MakeWithExplicitSize(sem_ir.insts().size(),
nullptr)),
constants_(LoweredConstantStore::MakeWithExplicitSize(
sem_ir.insts().size(), nullptr)),
lowered_specifics_(sem_ir.generics(), {}),
lowered_specifics_type_fingerprint_(sem_ir.specifics(), {}),
lowered_specific_fingerprint_(sem_ir.specifics(), {}),
equivalent_specifics_(sem_ir.specifics(), SemIR::SpecificId::None) {
// Initialization that relies on invariants of the class.
cpp_code_generator_ = CreateCppCodeGenerator();
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 {
if (cpp_code_generator_) {
// Clang code generation should not actually modify the AST, but isn't
// const-correct.
cpp_code_generator_->Initialize(
const_cast<clang::ASTContext&>(cpp_ast()->getASTContext()));
}
// 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(sem_ir_->types().GetInstId(type_id)));
}
}
// Lower function declarations.
for (auto [id, _] : sem_ir_->functions().enumerate()) {
functions_.Set(id, BuildFunctionDecl(id));
}
// Lower constants.
LowerConstants(*this, constants_);
}
// TODO: Move this to lower.cpp.
auto FileContext::LowerDefinitions() -> void {
for (const auto& class_info : sem_ir_->classes().values()) {
if (auto* llvm_vtable = BuildVtable(class_info)) {
global_variables_.Insert(class_info.vtable_id, llvm_vtable);
}
}
// Lower global variable definitions.
// TODO: Storing both a `constants_` array and a separate `global_variables_`
// map is redundant.
for (auto inst_id :
sem_ir().inst_blocks().Get(sem_ir().top_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 {
llvm_var = BuildGlobalVariableDecl(*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()));
}
}
// 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()) {
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(),
GetFunction(sem_ir().global_ctor_id()),
/*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_ast()->getASTContext()));
bool link_error = llvm::Linker::linkModules(
/*Dest=*/llvm_module(),
/*Src=*/std::unique_ptr<llvm::Module>(
cpp_code_generator_->ReleaseModule()));
CARBON_CHECK(!link_error);
}
// Find equivalent specifics (from the same generic), replace all uses and
// remove duplicately lowered function definitions.
CoalesceEquivalentSpecifics();
}
auto FileContext::InsertPair(
SemIR::SpecificId specific_id1, SemIR::SpecificId specific_id2,
Set<std::pair<SemIR::SpecificId, SemIR::SpecificId>>& set_of_pairs)
-> bool {
if (specific_id1.index > specific_id2.index) {
std::swap(specific_id1.index, specific_id2.index);
}
auto insert_result =
set_of_pairs.Insert(std::make_pair(specific_id1, specific_id2));
return insert_result.is_inserted();
}
auto FileContext::ContainsPair(
SemIR::SpecificId specific_id1, SemIR::SpecificId specific_id2,
const Set<std::pair<SemIR::SpecificId, SemIR::SpecificId>>& set_of_pairs)
-> bool {
if (specific_id1.index > specific_id2.index) {
std::swap(specific_id1.index, specific_id2.index);
}
return set_of_pairs.Contains(std::make_pair(specific_id1, specific_id2));
}
auto FileContext::CoalesceEquivalentSpecifics() -> void {
for (auto& specifics : lowered_specifics_.values()) {
// i cannot be unsigned due to the comparison with a negative number when
// the specifics vector is empty.
for (int i = 0; i < static_cast<int>(specifics.size()) - 1; ++i) {
// This specific was already replaced, skip it.
if (equivalent_specifics_.Get(specifics[i]).has_value() &&
equivalent_specifics_.Get(specifics[i]) != specifics[i]) {
specifics[i] = specifics[specifics.size() - 1];
specifics.pop_back();
--i;
continue;
}
// TODO: Improve quadratic behavior by using a single hash based on
// `lowered_specifics_type_fingerprint_` and `common_fingerprint`.
for (int j = i + 1; j < static_cast<int>(specifics.size()); ++j) {
// When the specific was already replaced, skip it.
if (equivalent_specifics_.Get(specifics[j]).has_value() &&
equivalent_specifics_.Get(specifics[j]) != specifics[j]) {
specifics[j] = specifics[specifics.size() - 1];
specifics.pop_back();
--j;
continue;
}
// When the two specifics are not equivalent due to the function type
// info stored in lowered_specifics_types, mark non-equivalance. This
// can be reused to short-cut another path and continue the search for
// other equivalences.
if (!AreFunctionTypesEquivalent(specifics[i], specifics[j])) {
InsertPair(specifics[i], specifics[j], non_equivalent_specifics_);
continue;
}
Set<std::pair<SemIR::SpecificId, SemIR::SpecificId>>
visited_equivalent_specifics;
InsertPair(specifics[i], specifics[j], visited_equivalent_specifics);
// Function type information matches; check usages inside the function
// body that are dependent on the specific. This information has been
// stored in lowered_states while lowering each function body.
if (AreFunctionBodiesEquivalent(specifics[i], specifics[j],
visited_equivalent_specifics)) {
// When processing equivalences, we may change the canonical specific
// multiple times, so we don't delete replaced specifics until the
// end.
llvm::SmallVector<SemIR::SpecificId> specifics_to_delete;
visited_equivalent_specifics.ForEach(
[&](std::pair<SemIR::SpecificId, SemIR::SpecificId>
equivalent_entry) {
CARBON_VLOG("Found equivalent specifics: {0}, {1}",
equivalent_entry.first, equivalent_entry.second);
ProcessSpecificEquivalence(equivalent_entry,
specifics_to_delete);
});
// Delete function bodies for already replaced functions.
for (auto specific_id : specifics_to_delete) {
specific_functions_.Get(specific_id)->eraseFromParent();
specific_functions_.Get(specific_id) =
specific_functions_.Get(equivalent_specifics_.Get(specific_id));
}
// Removed the replaced specific from the list of emitted specifics.
// Only the top level, since the others are somewhere else in the
// vector, they will be found and removed during processing.
specifics[j] = specifics[specifics.size() - 1];
specifics.pop_back();
--j;
} else {
// Only mark non-equivalence based on state for starting specifics.
InsertPair(specifics[i], specifics[j], non_equivalent_specifics_);
}
}
}
}
}
auto FileContext::ProcessSpecificEquivalence(
std::pair<SemIR::SpecificId, SemIR::SpecificId> pair,
llvm::SmallVector<SemIR::SpecificId>& specifics_to_delete) -> void {
auto [specific_id1, specific_id2] = pair;
CARBON_CHECK(specific_id1.has_value() && specific_id2.has_value(),
"Expected values in equivalence check");
auto get_canon = [&](SemIR::SpecificId specific_id) {
return equivalent_specifics_.Get(specific_id).has_value()
? std::make_pair(
equivalent_specifics_.Get(specific_id),
(equivalent_specifics_.Get(specific_id) != specific_id))
: std::make_pair(specific_id, false);
};
auto [canon_id1, replaced_before1] = get_canon(specific_id1);
auto [canon_id2, replaced_before2] = get_canon(specific_id2);
if (canon_id1 == canon_id2) {
// Already equivalent, there was a previous replacement.
return;
}
if (canon_id1.index >= canon_id2.index) {
// Prefer the earlier index for canonical values.
std::swap(canon_id1, canon_id2);
std::swap(replaced_before1, replaced_before2);
}
// Update equivalent_specifics_ for all. This is used as an indicator that
// this specific_id may be the canonical one when reducing the equivalence
// chains in `IsKnownEquivalence`.
equivalent_specifics_.Set(specific_id1, canon_id1);
equivalent_specifics_.Set(specific_id2, canon_id1);
specific_functions_.Get(canon_id2)->replaceAllUsesWith(
specific_functions_.Get(canon_id1));
if (!replaced_before2) {
specifics_to_delete.push_back(canon_id2);
}
}
auto FileContext::IsKnownEquivalence(SemIR::SpecificId specific_id1,
SemIR::SpecificId specific_id2) -> bool {
if (!equivalent_specifics_.Get(specific_id1).has_value() ||
!equivalent_specifics_.Get(specific_id2).has_value()) {
return false;
}
auto update_equivalent_specific = [&](SemIR::SpecificId specific_id) {
llvm::SmallVector<SemIR::SpecificId> stack;
SemIR::SpecificId specific_to_update = specific_id;
while (equivalent_specifics_.Get(
equivalent_specifics_.Get(specific_to_update)) !=
equivalent_specifics_.Get(specific_to_update)) {
stack.push_back(specific_to_update);
specific_to_update = equivalent_specifics_.Get(specific_to_update);
}
for (auto specific : llvm::reverse(stack)) {
equivalent_specifics_.Set(
specific,
equivalent_specifics_.Get(equivalent_specifics_.Get(specific)));
}
};
update_equivalent_specific(specific_id1);
update_equivalent_specific(specific_id2);
return equivalent_specifics_.Get(specific_id1) ==
equivalent_specifics_.Get(specific_id2);
}
auto FileContext::AreFunctionTypesEquivalent(SemIR::SpecificId specific_id1,
SemIR::SpecificId specific_id2)
-> bool {
CARBON_CHECK(specific_id1.has_value() && specific_id2.has_value());
return lowered_specifics_type_fingerprint_.Get(specific_id1) ==
lowered_specifics_type_fingerprint_.Get(specific_id2);
}
auto FileContext::AreFunctionBodiesEquivalent(
SemIR::SpecificId specific_id1, SemIR::SpecificId specific_id2,
Set<std::pair<SemIR::SpecificId, SemIR::SpecificId>>&
visited_equivalent_specifics) -> bool {
llvm::SmallVector<std::pair<SemIR::SpecificId, SemIR::SpecificId>> worklist;
worklist.push_back({specific_id1, specific_id2});
while (!worklist.empty()) {
auto outer_pair = worklist.pop_back_val();
auto [specific_id1, specific_id2] = outer_pair;
auto state1 = lowered_specific_fingerprint_.Get(specific_id1);
auto state2 = lowered_specific_fingerprint_.Get(specific_id2);
if (state1.common_fingerprint != state2.common_fingerprint) {
InsertPair(specific_id1, specific_id2, non_equivalent_specifics_);
return false;
}
if (state1.specific_fingerprint == state2.specific_fingerprint) {
continue;
}
// A size difference should have been detected by the common fingerprint.
CARBON_CHECK(state1.calls.size() == state2.calls.size(),
"Number of specific calls expected to be the same.");
for (auto [state1_call, state2_call] :
llvm::zip(state1.calls, state2.calls)) {
if (state1_call != state2_call) {
if (ContainsPair(state1_call, state2_call, non_equivalent_specifics_)) {
return false;
}
if (IsKnownEquivalence(state1_call, state2_call)) {
continue;
}
if (!InsertPair(state1_call, state2_call,
visited_equivalent_specifics)) {
continue;
}
// Leave the added equivalence pair in place and continue.
worklist.push_back({state1_call, state2_call});
}
}
}
return true;
}
auto FileContext::CreateCppCodeGenerator()
-> std::unique_ptr<clang::CodeGenerator> {
if (!cpp_ast()) {
return nullptr;
}
RawStringOstream clang_module_name_stream;
clang_module_name_stream << llvm_module().getName() << ".clang";
// Do not emit Clang's name and version as the creator of the output file.
cpp_code_gen_options_.EmitVersionIdentMetadata = false;
return std::unique_ptr<clang::CodeGenerator>(clang::CreateLLVMCodeGen(
cpp_ast()->getASTContext().getDiagnostics(),
clang_module_name_stream.TakeStr(), context().file_system(),
cpp_header_search_options_, cpp_preprocessor_options_,
cpp_code_gen_options_, llvm_context()));
}
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::Initializing:
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::Mixed:
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::GetOrCreateFunction(SemIR::FunctionId function_id,
SemIR::SpecificId specific_id)
-> llvm::Function* {
// If we have already lowered a declaration of this function, just return it.
auto** result = GetFunctionAddr(function_id, specific_id);
if (!*result) {
*result = BuildFunctionDecl(function_id, specific_id);
}
return *result;
}
auto FileContext::BuildFunctionTypeInfo(const SemIR::Function& function,
SemIR::SpecificId specific_id)
-> FunctionTypeInfo {
const auto return_info =
SemIR::ReturnTypeInfo::ForFunction(sem_ir(), function, specific_id);
if (!return_info.is_valid()) {
// The return type has not been completed, create a trivial type instead.
return {.type =
llvm::FunctionType::get(llvm::Type::getVoidTy(llvm_context()),
/*isVarArg=*/false)};
}
auto get_llvm_type = [&](SemIR::TypeId type_id) -> llvm::Type* {
if (!type_id.has_value()) {
return nullptr;
}
return GetType(type_id);
};
// TODO: expose the `Call` parameter patterns in `Function`, and use them here
// instead of reconstructing them via the syntactic parameter lists.
auto implicit_param_patterns =
sem_ir().inst_blocks().GetOrEmpty(function.implicit_param_patterns_id);
auto param_patterns =
sem_ir().inst_blocks().GetOrEmpty(function.param_patterns_id);
auto* return_type = get_llvm_type(return_info.type_id);
llvm::SmallVector<llvm::Type*> param_types;
// Compute the return type to use for the LLVM function. If the initializing
// representation doesn't produce a value, set the return type to void.
// TODO: For the `Run` entry point, remap return type to i32 if it doesn't
// return a value.
llvm::Type* function_return_type =
(return_info.is_valid() &&
return_info.init_repr.kind == SemIR::InitRepr::ByCopy)
? return_type
: llvm::Type::getVoidTy(llvm_context());
// TODO: Consider either storing `param_inst_ids` somewhere so that we can
// reuse it from `BuildFunctionDefinition` and when building calls, or factor
// out a mechanism to compute the mapping between parameters and arguments on
// demand.
llvm::SmallVector<SemIR::InstId> param_inst_ids;
auto max_llvm_params = (return_info.has_return_slot() ? 1 : 0) +
implicit_param_patterns.size() + param_patterns.size();
param_types.reserve(max_llvm_params);
param_inst_ids.reserve(max_llvm_params);
auto return_param_id = SemIR::InstId::None;
if (return_info.has_return_slot()) {
param_types.push_back(
llvm::PointerType::get(llvm_context(), /*AddressSpace=*/0));
return_param_id = function.return_slot_pattern_id;
param_inst_ids.push_back(return_param_id);
}
for (auto param_pattern_id : llvm::concat<const SemIR::InstId>(
implicit_param_patterns, param_patterns)) {
auto param_pattern_info = SemIR::Function::GetParamPatternInfoFromPatternId(
sem_ir(), param_pattern_id);
if (!param_pattern_info) {
continue;
}
auto param_type_id = ExtractScrutineeType(
sem_ir(), SemIR::GetTypeOfInstInSpecific(sem_ir(), specific_id,
param_pattern_info->inst_id));
CARBON_CHECK(
!param_type_id.AsConstantId().is_symbolic(),
"Found symbolic type id after resolution when lowering type {0}.",
param_pattern_info->inst.type_id);
switch (auto value_rep = SemIR::ValueRepr::ForType(sem_ir(), param_type_id);
value_rep.kind) {
case SemIR::ValueRepr::Unknown:
// This parameter type is incomplete. Fallback to describing the
// function type as `void()`.
return {.type = llvm::FunctionType::get(
llvm::Type::getVoidTy(llvm_context()),
/*isVarArg=*/false)};
case SemIR::ValueRepr::None:
break;
case SemIR::ValueRepr::Copy:
case SemIR::ValueRepr::Custom:
case SemIR::ValueRepr::Pointer:
auto* param_types_to_add = get_llvm_type(value_rep.type_id);
param_types.push_back(param_types_to_add);
param_inst_ids.push_back(param_pattern_id);
break;
}
}
return {.type = llvm::FunctionType::get(function_return_type, param_types,
/*isVarArg=*/false),
.param_inst_ids = std::move(param_inst_ids),
.return_type = return_type,
.return_param_id = return_param_id};
}
auto FileContext::HandleReferencedCppFunction(clang::FunctionDecl* cpp_decl)
-> void {
// TODO: To support recursive inline functions, collect all calls to
// `HandleTopLevelDecl()` in a custom `ASTConsumer` configured in the
// `ASTUnit`, and replay them in lowering in the `CodeGenerator`. See
// https://discord.com/channels/655572317891461132/768530752592805919/1370509111585935443
clang::FunctionDecl* cpp_def = cpp_decl->getDefinition();
if (!cpp_def) {
return;
}
// Create the LLVM function (`CodeGenModule::GetOrCreateLLVMFunction()`)
// so that code generation (`CodeGenModule::EmitGlobal()`) would see this
// function name (`CodeGenModule::getMangledName()`), and will generate
// its definition.
llvm::Constant* function_address =
cpp_code_generator_->GetAddrOfGlobal(clang::GlobalDecl(cpp_def),
/*isForDefinition=*/false);
CARBON_CHECK(function_address);
// Emit the function code.
cpp_code_generator_->HandleTopLevelDecl(clang::DeclGroupRef(cpp_def));
}
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.
llvm::BLAKE3 function_type_fingerprint;
RawStringOstream os;
llvm_type->print(os);
function_type_fingerprint.update(os.TakeStr());
function_type_fingerprint.final(
lowered_specifics_type_fingerprint_.Get(specific_id));
}
auto FileContext::BuildFunctionDecl(SemIR::FunctionId function_id,
SemIR::SpecificId specific_id)
-> llvm::Function* {
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 nullptr;
}
// Don't lower builtins.
if (function.builtin_function_kind() != SemIR::BuiltinFunctionKind::None) {
return nullptr;
}
// TODO: Consider tracking whether the function has been used, and only
// lowering it if it's needed.
auto function_type_info = BuildFunctionTypeInfo(function, specific_id);
// TODO: For an imported inline function, consider generating an
// `available_externally` definition.
auto linkage = specific_id.has_value() ? llvm::Function::LinkOnceODRLinkage
: llvm::Function::ExternalLinkage;
Mangler m(*this);
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: 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 C++ function, tell Clang that we referenced it.
if (auto clang_decl_id = sem_ir().functions().Get(function_id).clang_decl_id;
clang_decl_id.has_value()) {
CARBON_CHECK(!specific_id.has_value(),
"Specific functions cannot have C++ definitions");
HandleReferencedCppFunction(clang::dyn_cast<clang::FunctionDecl>(
sem_ir().clang_decls().Get(clang_decl_id)));
// TODO: Check that the signature and mangling generated by Clang and the
// one we generated are the same.
}
// 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, linkage,
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 [inst_id, arg] : llvm::zip_equal(function_type_info.param_inst_ids,
llvm_function->args())) {
auto name_id = SemIR::NameId::None;
if (inst_id == function_type_info.return_param_id) {
name_id = SemIR::NameId::ReturnSlot;
arg.addAttr(llvm::Attribute::getWithStructRetType(
llvm_context(), function_type_info.return_type));
} else {
name_id = SemIR::GetPrettyNameFromPatternId(sem_ir(), inst_id);
}
arg.setName(sem_ir().names().GetIRBaseName(name_id));
}
return llvm_function;
}
// 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* llvm_function = GetFunction(function_id, specific_id);
CARBON_CHECK(llvm_function,
"Attempting to define function that was not declared");
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);
}
FunctionContext function_lowering(
definition_context, llvm_function, *this, specific_id,
InitializeFingerprintForSpecific(specific_id),
definition_context.BuildDISubprogram(definition_function, llvm_function),
vlog_stream_);
// Add parameters to locals.
// TODO: This duplicates the mapping between sem_ir instructions and LLVM
// function parameters that was already computed in BuildFunctionDecl.
// We should only do that once.
auto call_param_ids = definition_ir.inst_blocks().GetOrEmpty(
definition_function.call_params_id);
int param_index = 0;
// TODO: Find a way to ensure this code and the function-call lowering use
// the same parameter ordering.
// Lowers the given parameter. Must be called in LLVM calling convention
// parameter order.
auto lower_param = [&](SemIR::InstId param_id) {
// Get the value of the parameter from the function argument.
auto param_inst = definition_ir.insts().GetAs<SemIR::AnyParam>(param_id);
llvm::Value* param_value;
if (SemIR::ValueRepr::ForType(definition_ir, param_inst.type_id).kind !=
SemIR::ValueRepr::None) {
param_value = llvm_function->getArg(param_index);
++param_index;
} else {
param_value = llvm::PoisonValue::get(
function_lowering.GetTypeOfInstInSpecific(param_id));
}
// The value of the parameter is the value of the argument.
function_lowering.SetLocal(param_id, param_value);
};
// The subset of call_param_ids that is already in the order that the LLVM
// calling convention expects.
llvm::ArrayRef<SemIR::InstId> sequential_param_ids;
if (declaration_function.return_slot_pattern_id.has_value()) {
// The LLVM calling convention has the return slot first rather than last.
// Note that this queries whether there is a return slot at the LLVM level,
// whereas `function.return_slot_pattern_id.has_value()` queries whether
// there is a return slot at the SemIR level.
if (SemIR::ReturnTypeInfo::ForFunction(sem_ir(), declaration_function,
specific_id)
.has_return_slot()) {
lower_param(call_param_ids.back());
}
sequential_param_ids = call_param_ids.drop_back();
} else {
sequential_param_ids = call_param_ids;
}
for (auto param_id : sequential_param_ids) {
lower_param(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(llvm_function->end());
function_lowering.builder().SetInsertPoint(llvm_block);
function_lowering.LowerBlockContents(block_id);
};
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 = &llvm_function->getEntryBlock();
if (entry_block->hasNPredecessorsOrMore(1)) {
auto* new_entry_block = llvm::BasicBlock::Create(
llvm_context(), "entry", llvm_function, entry_block);
llvm::BranchInst::Create(entry_block, new_entry_block);
}
// Emit fingerprint accumulated inside the function context.
function_lowering.EmitFinalFingerprint();
}
auto FileContext::BuildDISubprogram(const SemIR::Function& function,
const llvm::Function* llvm_function)
-> 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);
// TODO: Add more details here, including real subroutine type (once type
// information is built), etc.
return context().di_builder().createFunction(
context().di_compile_unit(), *name, llvm_function->getName(),
/*File=*/context().di_builder().createFile(loc.filename, ""),
/*LineNo=*/loc.line_number,
context().di_builder().createSubroutineType(
context().di_builder().getOrCreateTypeArray(std::nullopt)),
/*ScopeLine=*/0, llvm::DINode::FlagZero,
llvm::DISubprogram::SPFlagDefinition);
}
// BuildTypeForInst is used to construct types for FileContext::BuildType below.
// Implementations return the LLVM type for the instruction. This first overload
// is the fallback handler for non-type instructions.
template <typename InstT>
requires(InstT::Kind.is_type() == SemIR::InstIsType::Never)
static auto BuildTypeForInst(FileContext& /*context*/, InstT inst)
-> llvm::Type* {
CARBON_FATAL("Cannot use inst as type: {0}", inst);
}
template <typename InstT>
requires(InstT::Kind.is_symbolic_when_type())
static auto BuildTypeForInst(FileContext& context, InstT /*inst*/)
-> llvm::Type* {
// Treat non-monomorphized symbolic types as opaque.
return llvm::StructType::get(context.llvm_context());
}
static auto BuildTypeForInst(FileContext& context, SemIR::ArrayType inst)
-> llvm::Type* {
return llvm::ArrayType::get(
context.GetType(context.sem_ir().types().GetTypeIdForTypeInstId(
inst.element_type_inst_id)),
*context.sem_ir().GetArrayBoundValue(inst.bound_id));
}
static auto BuildTypeForInst(FileContext& /*context*/, SemIR::AutoType inst)
-> llvm::Type* {
CARBON_FATAL("Unexpected builtin type in lowering: {0}", inst);
}
static auto BuildTypeForInst(FileContext& context, SemIR::BoolType /*inst*/)
-> llvm::Type* {
// TODO: We may want to have different representations for `bool` storage
// (`i8`) versus for `bool` values (`i1`).
return llvm::Type::getInt1Ty(context.llvm_context());
}
static auto BuildTypeForInst(FileContext& context, SemIR::ClassType inst)
-> llvm::Type* {
auto object_repr_id = context.sem_ir()
.classes()
.Get(inst.class_id)
.GetObjectRepr(context.sem_ir(), inst.specific_id);
return context.GetType(object_repr_id);
}
static auto BuildTypeForInst(FileContext& context, SemIR::ConstType inst)
-> llvm::Type* {
return context.GetType(
context.sem_ir().types().GetTypeIdForTypeInstId(inst.inner_id));
}
static auto BuildTypeForInst(FileContext& context,
SemIR::ImplWitnessAssociatedConstant inst)
-> llvm::Type* {
return context.GetType(inst.type_id);
}
static auto BuildTypeForInst(FileContext& /*context*/,
SemIR::ErrorInst /*inst*/) -> llvm::Type* {
// This is a complete type but uses of it should never be lowered.
return nullptr;
}
static auto BuildTypeForInst(FileContext& context, SemIR::FloatType /*inst*/)
-> llvm::Type* {
// TODO: Handle different sizes.
return llvm::Type::getDoubleTy(context.llvm_context());
}
static auto BuildTypeForInst(FileContext& context, SemIR::IntType inst)
-> llvm::Type* {
auto width =
context.sem_ir().insts().TryGetAs<SemIR::IntValue>(inst.bit_width_id);
CARBON_CHECK(width, "Can't lower int type with symbolic width");
return llvm::IntegerType::get(
context.llvm_context(),
context.sem_ir().ints().Get(width->int_id).getZExtValue());
}
static auto BuildTypeForInst(FileContext& context,
SemIR::LegacyFloatType /*inst*/) -> llvm::Type* {
return llvm::Type::getDoubleTy(context.llvm_context());
}
static auto BuildTypeForInst(FileContext& context, SemIR::PointerType /*inst*/)
-> llvm::Type* {
return llvm::PointerType::get(context.llvm_context(), /*AddressSpace=*/0);
}
static auto BuildTypeForInst(FileContext& /*context*/,
SemIR::PatternType /*inst*/) -> llvm::Type* {
CARBON_FATAL("Unexpected pattern type in lowering");
}
static auto BuildTypeForInst(FileContext& context, SemIR::StructType inst)
-> llvm::Type* {
auto fields = context.sem_ir().struct_type_fields().Get(inst.fields_id);
llvm::SmallVector<llvm::Type*> subtypes;
subtypes.reserve(fields.size());
for (auto field : fields) {
subtypes.push_back(context.GetType(
context.sem_ir().types().GetTypeIdForTypeInstId(field.type_inst_id)));
}
return llvm::StructType::get(context.llvm_context(), subtypes);
}
static auto BuildTypeForInst(FileContext& context, SemIR::TupleType inst)
-> llvm::Type* {
// TODO: Investigate special-casing handling of empty tuples so that they
// can be collectively replaced with LLVM's void, particularly around
// function returns. LLVM doesn't allow declaring variables with a void
// type, so that may require significant special casing.
auto elements = context.sem_ir().inst_blocks().Get(inst.type_elements_id);
llvm::SmallVector<llvm::Type*> subtypes;
subtypes.reserve(elements.size());
for (auto type_id : context.sem_ir().types().GetBlockAsTypeIds(elements)) {
subtypes.push_back(context.GetType(type_id));
}
return llvm::StructType::get(context.llvm_context(), subtypes);
}
static auto BuildTypeForInst(FileContext& context, SemIR::TypeType /*inst*/)
-> llvm::Type* {
return context.GetTypeType();
}
static auto BuildTypeForInst(FileContext& context, SemIR::VtableType /*inst*/)
-> llvm::Type* {
return llvm::Type::getVoidTy(context.llvm_context());
}
template <typename InstT>
requires(InstT::Kind.template IsAnyOf<SemIR::SpecificFunctionType,
SemIR::StringType>())
static auto BuildTypeForInst(FileContext& context, InstT /*inst*/)
-> llvm::Type* {
// TODO: Decide how we want to represent `StringType`.
return llvm::PointerType::get(context.llvm_context(), 0);
}
template <typename InstT>
requires(InstT::Kind
.template IsAnyOf<SemIR::BoundMethodType, SemIR::IntLiteralType,
SemIR::NamespaceType, SemIR::WitnessType>())
static auto BuildTypeForInst(FileContext& context, InstT /*inst*/)
-> llvm::Type* {
// Return an empty struct as a placeholder.
return llvm::StructType::get(context.llvm_context());
}
template <typename InstT>
requires(InstT::Kind.template IsAnyOf<
SemIR::AssociatedEntityType, SemIR::FacetType, SemIR::FunctionType,
SemIR::FunctionTypeWithSelfType, SemIR::GenericClassType,
SemIR::GenericInterfaceType, SemIR::InstType,
SemIR::UnboundElementType, SemIR::WhereExpr>())
static auto BuildTypeForInst(FileContext& context, InstT /*inst*/)
-> llvm::Type* {
// Return an empty struct as a placeholder.
// TODO: Should we model an interface as a witness table, or an associated
// entity as an index?
return llvm::StructType::get(context.llvm_context());
}
auto FileContext::BuildType(SemIR::InstId inst_id) -> llvm::Type* {
// Use overload resolution to select the implementation, producing compile
// errors when BuildTypeForInst isn't defined for a given instruction.
CARBON_KIND_SWITCH(sem_ir_->insts().Get(inst_id)) {
#define CARBON_SEM_IR_INST_KIND(Name) \
case CARBON_KIND(SemIR::Name inst): { \
return BuildTypeForInst(*this, inst); \
}
#include "toolchain/sem_ir/inst_kind.def"
}
}
auto FileContext::BuildGlobalVariableDecl(SemIR::VarStorage var_storage)
-> llvm::GlobalVariable* {
Mangler m(*this);
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 {
return context().GetLocForDI(
GetAbsoluteNodeId(sem_ir_, SemIR::LocId(inst_id)).back());
}
auto FileContext::BuildVtable(const SemIR::Class& class_info)
-> llvm::GlobalVariable* {
// Bail out if this class is not dynamic (this will account for classes that
// are declared-and-not-defined (including extern declarations) as well).
if (!class_info.is_dynamic) {
return nullptr;
}
// 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 != SemIR::GenericId::None) {
return nullptr;
}
Mangler m(*this);
std::string mangled_name = m.MangleVTable(class_info);
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 canonical_vtable_id =
sem_ir().constant_values().GetConstantInstId(class_info.vtable_id);
auto vtable_inst_block =
sem_ir().inst_blocks().Get(sem_ir()
.insts()
.GetAs<SemIR::Vtable>(canonical_vtable_id)
.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 fn_decl = GetCalleeFunction(sem_ir(), fn_decl_id);
vfuncs.push_back(llvm::ConstantExpr::getTrunc(
llvm::ConstantExpr::getSub(
llvm::ConstantExpr::getPtrToInt(
GetOrCreateFunction(fn_decl.function_id,
SemIR::SpecificId::None),
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
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