Split a cross-file Lower::Context out of Lower::FileContext. (#5583)

In preparation for lowering information from multiple `SemIR::File`s into a single `llvm::Module`. The primary purpose of this is to support lowering a local specific for an imported generic function, where the instructions for the generic function are in a different file than the instructions for the specific. See #5475 for a draft PR implementing that functionality on top of this. The per-`llvm::Module` state now lives in `Lower::Context`, and `Lower::FileContext` tracks only the per-`SemIR::File` information. `Lower::Context` should not mention any `SemIR` IDs that are file-specific. For now, the C++ lowering and the specific coalescing logic are kept per-file for simplicity.
2026-10-05 22:02:55 +01:00 · 2025-06-02 18:02:32 +00:00
parent 0fd129ec95
commit e91840e1b6
9 changed files with 309 additions and 172 deletions
@@ -0,0 +1,88 @@
+// 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/context.h"
+
+#include "common/check.h"
+#include "common/vlog.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+#include "toolchain/lower/file_context.h"
+#include "toolchain/sem_ir/inst_namer.h"
+
+namespace Carbon::Lower {
+
+Context::Context(llvm::LLVMContext& llvm_context,
+                 llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> fs,
+                 std::optional<llvm::ArrayRef<Parse::GetTreeAndSubtreesFn>>
+                     tree_and_subtrees_getters_for_debug_info,
+                 llvm::StringRef module_name, llvm::raw_ostream* vlog_stream)
+    : llvm_context_(&llvm_context),
+      llvm_module_(std::make_unique<llvm::Module>(module_name, llvm_context)),
+      file_system_(std::move(fs)),
+      di_builder_(*llvm_module_),
+      di_compile_unit_(
+          tree_and_subtrees_getters_for_debug_info
+              ? BuildDICompileUnit(module_name, *llvm_module_, di_builder_)
+              : nullptr),
+      tree_and_subtrees_getters_for_debug_info_(
+          tree_and_subtrees_getters_for_debug_info),
+      vlog_stream_(vlog_stream) {}
+
+auto Context::GetFileContext(const SemIR::File* file,
+                             const SemIR::InstNamer* inst_namer)
+    -> FileContext& {
+  auto insert_result = file_contexts_.Insert(file->check_ir_id(), [&] {
+    auto file_context =
+        std::make_unique<FileContext>(*this, *file, inst_namer, vlog_stream_);
+    file_context->PrepareToLower();
+    return file_context;
+  });
+  return *insert_result.value();
+}
+
+auto Context::Finalize() && -> std::unique_ptr<llvm::Module> {
+  file_contexts_.ForEach(
+      [](auto, auto& file_context) { file_context->Finalize(); });
+  return std::move(llvm_module_);
+}
+
+auto Context::BuildDICompileUnit(llvm::StringRef module_name,
+                                 llvm::Module& llvm_module,
+                                 llvm::DIBuilder& di_builder)
+    -> llvm::DICompileUnit* {
+  llvm_module.addModuleFlag(llvm::Module::Max, "Dwarf Version", 5);
+  llvm_module.addModuleFlag(llvm::Module::Warning, "Debug Info Version",
+                            llvm::DEBUG_METADATA_VERSION);
+  // TODO: Include directory path in the compile_unit_file.
+  llvm::DIFile* compile_unit_file = di_builder.createFile(module_name, "");
+  // TODO: Introduce a new language code for Carbon. C works well for now since
+  // it's something debuggers will already know/have support for at least.
+  // Probably have to bump to C++ at some point for virtual functions,
+  // templates, etc.
+  return di_builder.createCompileUnit(llvm::dwarf::DW_LANG_C, compile_unit_file,
+                                      "carbon",
+                                      /*isOptimized=*/false, /*Flags=*/"",
+                                      /*RV=*/0);
+}
+
+auto Context::GetLocForDI(SemIR::AbsoluteNodeId abs_node_id) -> LocForDI {
+  const auto& tree_and_subtrees =
+      (*tree_and_subtrees_getters_for_debug_info_)[abs_node_id.check_ir_id()
+                                                       .index]();
+  const auto& tokens = tree_and_subtrees.tree().tokens();
+
+  if (abs_node_id.node_id().has_value()) {
+    auto token =
+        tree_and_subtrees.GetSubtreeTokenRange(abs_node_id.node_id()).begin;
+    return {.filename = tokens.source().filename(),
+            .line_number = tokens.GetLineNumber(token),
+            .column_number = tokens.GetColumnNumber(token)};
+  } else {
+    return {.filename = tokens.source().filename(),
+            .line_number = 0,
+            .column_number = 0};
+  }
+}
+
+}  // namespace Carbon::Lower