Add a flag to build a single ASTContext shared across all compilations (#7567)

Instead of building one Clang `ASTContext` per compilation, the
`--share-cpp-ast` flag causes us to build a single `ASTContext` and
share it across all contexts. One new abstraction is added: `CppDomain`
represents the Carbon-side view of a Clang AST that might be shared
across multiple `SemIR::File`s. This object owns the Clang instance and
the AST.

For now, we have no isolation between the C++ state exposed to different
Carbon compilations, and we have no multiplexing of generated LLVM IR
from C++ into different Carbon compilations, so the mode is not usable
yet. The plan is to keep it behind a flag until it's ready.

Assisted-by: Gemini via Antigravity
This commit is contained in:
Richard Smith
2026-07-28 00:19:40 +00:00
committed by GitHub
parent 4e77f9b6c8
commit 7d89ac98c7
25 changed files with 449 additions and 211 deletions
@@ -36,23 +36,22 @@ fn MyF() {
// --- without_definition.h
// TODO: Promote this warning to an error by default.
// CHECK:STDERR: ./without_definition.h:[[@LINE+3]]:13: warning: inline function 'foo' is not defined [CppInteropParseWarning]
// CHECK:STDERR: 6 | inline void foo();
// CHECK:STDERR: | ^
inline void foo();
// --- todo_fail_import_without_definition.carbon
library "[[@TEST_NAME]]";
// TODO: Promote this warning to an error by default.
// CHECK:STDERR: todo_fail_import_without_definition.carbon:[[@LINE+4]]:10: in file included here [InCppInclude]
// CHECK:STDERR: ./without_definition.h:2:13: warning: inline function 'foo' is not defined [CppInteropParseWarning]
// CHECK:STDERR: 2 | inline void foo();
// CHECK:STDERR: | ^
import Cpp library "without_definition.h";
fn MyF() {
//@dump-sem-ir-begin
// CHECK:STDERR: todo_fail_import_without_definition.carbon:[[@LINE+4]]:11: note: used here [CppInteropParseNote]
// CHECK:STDERR: 17 | Cpp.foo();
// CHECK:STDERR: 12 | Cpp.foo();
// CHECK:STDERR: | ^
// CHECK:STDERR:
Cpp.foo();
@@ -134,12 +133,12 @@ fn MyF() {
// CHECK:STDOUT:
// CHECK:STDOUT: fn @MyF() {
// CHECK:STDOUT: !entry:
// CHECK:STDOUT: %Cpp.ref.loc17: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %foo.ref.loc17: %foo.cpp_overload_set.type = name_ref foo, imports.%foo.cpp_overload_set.value [concrete = constants.%foo.cpp_overload_set.value]
// CHECK:STDOUT: %foo.call.loc17: init %empty_tuple.type = call imports.%foo.decl()
// CHECK:STDOUT: %Cpp.ref.loc20: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %foo.ref.loc20: %foo.cpp_overload_set.type = name_ref foo, imports.%foo.cpp_overload_set.value [concrete = constants.%foo.cpp_overload_set.value]
// CHECK:STDOUT: %foo.call.loc20: init %empty_tuple.type = call imports.%foo.decl()
// CHECK:STDOUT: %Cpp.ref.loc12: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %foo.ref.loc12: %foo.cpp_overload_set.type = name_ref foo, imports.%foo.cpp_overload_set.value [concrete = constants.%foo.cpp_overload_set.value]
// CHECK:STDOUT: %foo.call.loc12: init %empty_tuple.type = call imports.%foo.decl()
// CHECK:STDOUT: %Cpp.ref.loc15: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %foo.ref.loc15: %foo.cpp_overload_set.type = name_ref foo, imports.%foo.cpp_overload_set.value [concrete = constants.%foo.cpp_overload_set.value]
// CHECK:STDOUT: %foo.call.loc15: init %empty_tuple.type = call imports.%foo.decl()
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: }
// CHECK:STDOUT: