Pass fission flags to ThinLTO backend actions (#837)
Fix interaction between `--fission` and `--features=thin_lto`. Without this, every LTO backend action fails:
```
ERROR: output 'prog.lto/bazel-out/k8-opt/bin/_objs/prog/a.dwo' was not created
ERROR: LTO Backend Compile prog.lto/bazel-out/k8-opt/bin/_objs/prog/a.o failed:
not all outputs were created or valid
```
Fixed by adding `ACTION_NAMES.lto_backend` to the `per_object_debug_info` flag_set in
`cc/private/toolchain/unix_cc_toolchain_config.bzl` and `cc/private/toolchain_config/legacy_features.bzl`.
Adds a test that uses the real Linux `cc_toolchain_config` since that wasn't covered by the existing test, and was broken.
Closes #837
COPYBARA_INTEGRATE_REVIEW=https://github.com/bazelbuild/rules_cc/pull/837 from akonradi:abakon/fission-flags-for-lto-backend c033aba8813345a9c84a3f48cf11fb9bf970774d
PiperOrigin-RevId: 964562193
Change-Id: I09f0c92967f5d148dfa24edca0533e306a2647bb
diff --git a/cc/private/toolchain/unix_cc_toolchain_config.bzl b/cc/private/toolchain/unix_cc_toolchain_config.bzl
index 41ca311..4724887 100644
--- a/cc/private/toolchain/unix_cc_toolchain_config.bzl
+++ b/cc/private/toolchain/unix_cc_toolchain_config.bzl
@@ -781,6 +781,7 @@
ACTION_NAMES.cpp_compile,
ACTION_NAMES.cpp_module_codegen,
ACTION_NAMES.cpp20_module_codegen,
+ ACTION_NAMES.lto_backend,
],
flag_groups = [
flag_group(
diff --git a/cc/private/toolchain_config/legacy_features.bzl b/cc/private/toolchain_config/legacy_features.bzl
index c68e827..7a3b829 100644
--- a/cc/private/toolchain_config/legacy_features.bzl
+++ b/cc/private/toolchain_config/legacy_features.bzl
@@ -158,6 +158,7 @@
ACTION_NAMES.c_compile,
ACTION_NAMES.cpp_compile,
ACTION_NAMES.cpp_module_codegen,
+ ACTION_NAMES.lto_backend,
ACTION_NAMES.preprocess_assemble,
],
flag_groups = [flag_group(
diff --git a/tests/default_unix_toolchain/BUILD.bazel b/tests/default_unix_toolchain/BUILD.bazel
index f542230..63b9544 100644
--- a/tests/default_unix_toolchain/BUILD.bazel
+++ b/tests/default_unix_toolchain/BUILD.bazel
@@ -1,13 +1,20 @@
+load("//cc:cc_binary.bzl", "cc_binary")
load("//cc:cc_library.bzl", "cc_library")
load("//cc/private/toolchain:unix_cc_toolchain_config.bzl", "cc_toolchain_config") # buildifier: disable=bzl-visibility
load("//cc/toolchains:cc_toolchain.bzl", "cc_toolchain")
load(":unix_archiver_test.bzl", "unix_archiver_tests")
+load(":unix_fission_test.bzl", "unix_fission_tests")
platform(
name = "macos",
constraint_values = ["@platforms//os:macos"],
)
+platform(
+ name = "linux",
+ constraint_values = ["@platforms//os:linux"],
+)
+
filegroup(
name = "empty",
)
@@ -65,3 +72,58 @@
name = "unix_archiver_tests",
target = ":archive",
)
+
+cc_toolchain_config(
+ name = "linux_config",
+ abi_libc_version = "local",
+ abi_version = "local",
+ compiler = "compiler",
+ cpu = "k8",
+ host_system_name = "local",
+ supports_start_end_lib = True,
+ target_libc = "local",
+ target_system_name = "local",
+ tool_paths = {
+ "ar": "/usr/bin/ar",
+ "cpp": "/usr/bin/cpp",
+ "dwp": "/usr/bin/dwp",
+ "gcc": "/usr/bin/clang",
+ "ld": "/usr/bin/ld",
+ "nm": "/usr/bin/nm",
+ "objcopy": "/usr/bin/objcopy",
+ "objdump": "/usr/bin/objdump",
+ "strip": "/usr/bin/strip",
+ },
+ toolchain_identifier = "default-unix-linux-toolchain-test",
+)
+
+cc_toolchain(
+ name = "linux_cc_toolchain",
+ all_files = ":empty",
+ ar_files = ":empty",
+ as_files = ":empty",
+ compiler_files = ":empty",
+ dwp_files = ":empty",
+ linker_files = ":empty",
+ objcopy_files = ":empty",
+ strip_files = ":empty",
+ toolchain_config = ":linux_config",
+ toolchain_identifier = "default-unix-linux-toolchain-test",
+)
+
+toolchain(
+ name = "linux_cc_toolchain_registration",
+ target_compatible_with = ["@platforms//os:linux"],
+ toolchain = ":linux_cc_toolchain",
+ toolchain_type = "//cc:toolchain_type",
+)
+
+cc_binary(
+ name = "fission",
+ srcs = ["fission.cc"],
+)
+
+unix_fission_tests(
+ name = "unix_fission_tests",
+ target = ":fission",
+)
diff --git a/tests/default_unix_toolchain/fission.cc b/tests/default_unix_toolchain/fission.cc
new file mode 100644
index 0000000..4cce7f6
--- /dev/null
+++ b/tests/default_unix_toolchain/fission.cc
@@ -0,0 +1,3 @@
+int main() {
+ return 0;
+}
diff --git a/tests/default_unix_toolchain/unix_fission_test.bzl b/tests/default_unix_toolchain/unix_fission_test.bzl
new file mode 100644
index 0000000..2a864e3
--- /dev/null
+++ b/tests/default_unix_toolchain/unix_fission_test.bzl
@@ -0,0 +1,51 @@
+"""Tests for fission flags on ThinLTO backend actions in the default Unix toolchain."""
+
+load("@rules_testing//lib:analysis_test.bzl", "analysis_test")
+
+_LINUX_PLATFORM = str(Label("//tests/default_unix_toolchain:linux"))
+_LINUX_TOOLCHAIN = str(Label("//tests/default_unix_toolchain:linux_cc_toolchain_registration"))
+
+def _lto_backend_action(env, target):
+ backend_actions = [
+ action
+ for action in target.actions
+ if action.mnemonic == "CcLtoBackendCompile"
+ ]
+ env.expect.that_collection(backend_actions).has_size(1)
+ return backend_actions[0]
+
+def _fission_on_lto_backend_test_impl(env, target):
+ action = _lto_backend_action(env, target)
+
+ # Fission is enabled, so a .dwo output is declared for the backend action.
+ dwo_outputs = [
+ file.path
+ for file in action.outputs.to_list()
+ if file.path.endswith(".dwo")
+ ]
+ env.expect.that_collection(dwo_outputs).has_size(1)
+
+ # The backend action is the one that emits the object file, so it is the
+ # action that has to be told to split the debug info out of it.
+ env.expect.that_collection(action.argv).contains("-gsplit-dwarf")
+
+def unix_fission_tests(name, target):
+ analysis_test(
+ name = name + "_lto_backend_fission_flags",
+ target = target,
+ impl = _fission_on_lto_backend_test_impl,
+ config_settings = {
+ "//command_line_option:extra_toolchains": [_LINUX_TOOLCHAIN],
+ "//command_line_option:features": [
+ "thin_lto",
+ "per_object_debug_info",
+ ],
+ "//command_line_option:fission": ["yes"],
+ "//command_line_option:platforms": [_LINUX_PLATFORM],
+ },
+ )
+
+ native.test_suite(
+ name = name,
+ tests = [name + "_lto_backend_fission_flags"],
+ )
