[clang] [C++20] [Modules] Convert '-fexperimental-modules-reduced-bmi' to '-fmodules-reduced-bmi' (PR #114382)
Chuanqi Xu via cfe-commits
cfe-commits at lists.llvm.org
Tue Nov 5 00:19:23 PST 2024
https://github.com/ChuanqiXu9 updated https://github.com/llvm/llvm-project/pull/114382
>From f33e3bcd7d31742a37059a9d75fa58aa4d9ff36d Mon Sep 17 00:00:00 2001
From: Chuanqi Xu <yedeng.yd at linux.alibaba.com>
Date: Thu, 31 Oct 2024 17:27:00 +0800
Subject: [PATCH 1/3] [C++20] [Modules] Convert
'-fexperimental-modules-reduced-bmi' to '-fmodules-reduced-bmi'
---
clang/docs/StandardCPlusPlusModules.rst | 18 ++++++-------
.../clang/Basic/DiagnosticDriverKinds.td | 8 ++++++
clang/include/clang/Driver/Options.td | 5 +++-
clang/lib/Driver/ToolChains/Clang.cpp | 12 +++++++--
.../test/Driver/module-fgen-reduced-bmi.cppm | 26 +++++++++++++++++--
5 files changed, 55 insertions(+), 14 deletions(-)
diff --git a/clang/docs/StandardCPlusPlusModules.rst b/clang/docs/StandardCPlusPlusModules.rst
index 8e22adad15106e..26b29337ce42cb 100644
--- a/clang/docs/StandardCPlusPlusModules.rst
+++ b/clang/docs/StandardCPlusPlusModules.rst
@@ -602,16 +602,16 @@ unnecessary dependencies for the BMI. To mitigate the problem, Clang has a
compiler option to reduce the information contained in the BMI. These two
formats are known as Full BMI and Reduced BMI, respectively.
-Users can use the ``-fexperimental-modules-reduced-bmi`` option to produce a
+Users can use the ``-fmodules-reduced-bmi`` option to produce a
Reduced BMI.
For the one-phase compilation model (CMake implements this model), with
-``-fexperimental-modules-reduced-bmi``, the generated BMI will be a Reduced
+``-fmodules-reduced-bmi``, the generated BMI will be a Reduced
BMI automatically. (The output path of the BMI is specified by
``-fmodule-output=`` as usual with the one-phase compilation model).
It is also possible to produce a Reduced BMI with the two-phase compilation
-model. When ``-fexperimental-modules-reduced-bmi``, ``--precompile``, and
+model. When ``-fmodules-reduced-bmi``, ``--precompile``, and
``-fmodule-output=`` are specified, the generated BMI specified by ``-o`` will
be a full BMI and the BMI specified by ``-fmodule-output=`` will be a Reduced
BMI. The dependency graph in this case would look like:
@@ -625,7 +625,7 @@ BMI. The dependency graph in this case would look like:
-> ...
-> consumer_n.cpp
-Clang does not emit diagnostics when ``-fexperimental-modules-reduced-bmi`` is
+Clang does not emit diagnostics when ``-fmodules-reduced-bmi`` is
used with a non-module unit. This design permits users of the one-phase
compilation model to try using reduced BMIs without needing to modify the build
system. The two-phase compilation module requires build system support.
@@ -691,7 +691,7 @@ ensure it is reachable, e.g. ``using N::g;``.
Support for Reduced BMIs is still experimental, but it may become the default
in the future. The expected roadmap for Reduced BMIs as of Clang 19.x is:
-1. ``-fexperimental-modules-reduced-bmi`` is opt-in for 1~2 releases. The period depends
+1. ``-fmodules-reduced-bmi`` is opt-in for 1~2 releases. The period depends
on user feedback and may be extended.
2. Announce that Reduced BMIs are no longer experimental and introduce
``-fmodules-reduced-bmi`` as a new option, and recommend use of the new
@@ -814,8 +814,8 @@ With reduced BMI, non-cascading changes can be more powerful. For example,
.. code-block:: console
- $ clang++ -std=c++20 A.cppm -c -fmodule-output=A.pcm -fexperimental-modules-reduced-bmi -o A.o
- $ clang++ -std=c++20 B.cppm -c -fmodule-output=B.pcm -fexperimental-modules-reduced-bmi -o B.o -fmodule-file=A=A.pcm
+ $ clang++ -std=c++20 A.cppm -c -fmodule-output=A.pcm -fmodules-reduced-bmi -o A.o
+ $ clang++ -std=c++20 B.cppm -c -fmodule-output=B.pcm -fmodules-reduced-bmi -o B.o -fmodule-file=A=A.pcm
$ md5sum B.pcm
6c2bd452ca32ab418bf35cd141b060b9 B.pcm
@@ -831,8 +831,8 @@ and recompile the example:
.. code-block:: console
- $ clang++ -std=c++20 A.cppm -c -fmodule-output=A.pcm -fexperimental-modules-reduced-bmi -o A.o
- $ clang++ -std=c++20 B.cppm -c -fmodule-output=B.pcm -fexperimental-modules-reduced-bmi -o B.o -fmodule-file=A=A.pcm
+ $ clang++ -std=c++20 A.cppm -c -fmodule-output=A.pcm -fmodules-reduced-bmi -o A.o
+ $ clang++ -std=c++20 B.cppm -c -fmodule-output=B.pcm -fmodules-reduced-bmi -o B.o -fmodule-file=A=A.pcm
$ md5sum B.pcm
6c2bd452ca32ab418bf35cd141b060b9 B.pcm
diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index 65551bd7761a9d..7589c6f52419dd 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -556,6 +556,14 @@ def err_test_module_file_extension_format : Error<
def err_drv_module_output_with_multiple_arch : Error<
"option '-fmodule-output' can't be used with multiple arch options">;
+def warn_drv_module_reduced_bmi_not_enabled : Warning<
+ "reduced BMI is expected to be enabled by default in Clang 21. It is encouraged to "
+ "enable it ahead of time to avoid potential breaking change. You can enable it "
+ "by offering '-fmodules-reduced-bmi' option in one phase compilation model (e.g., CMake). "
+ "Or if your build system support two phase compilation model, please contact the "
+ "build system authors to support reduced BMI and turn off the warning temporarily">,
+ InGroup<DiagGroup<"missing-reduced-bmi">>;
+
def warn_drv_delayed_template_parsing_after_cxx20 : Warning<
"-fdelayed-template-parsing is deprecated after C++20">,
InGroup<DiagGroup<"delayed-template-parsing-in-cxx20">>;
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 2b9ee1a0e669ed..bd4a716db29b0a 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3194,11 +3194,14 @@ defm skip_odr_check_in_gmf : BoolOption<"f", "skip-odr-check-in-gmf",
"Perform ODR checks for decls in the global module fragment.">>,
Group<f_Group>;
-def modules_reduced_bmi : Flag<["-"], "fexperimental-modules-reduced-bmi">,
+def modules_reduced_bmi : Flag<["-"], "fmodules-reduced-bmi">,
Group<f_Group>, Visibility<[ClangOption, CC1Option]>,
HelpText<"Generate the reduced BMI">,
MarshallingInfoFlag<FrontendOpts<"GenReducedBMI">>;
+def experimental_modules_reduced_bmi : Flag<["-"], "fexperimental-modules-reduced-bmi">,
+ Group<f_Group>, Visibility<[ClangOption, CC1Option]>, Alias<modules_reduced_bmi>;
+
def fmodules_embed_all_files : Joined<["-"], "fmodules-embed-all-files">,
Visibility<[ClangOption, CC1Option, CLOption]>,
HelpText<"Embed the contents of all files read by this compilation into "
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 4c6f508f1f24a6..b67993d7b84d42 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4255,7 +4255,7 @@ static bool RenderModulesOptions(Compilation &C, const Driver &D,
if (Args.hasArg(options::OPT_modules_reduced_bmi) &&
(Input.getType() == driver::types::TY_CXXModule ||
Input.getType() == driver::types::TY_PP_CXXModule)) {
- CmdArgs.push_back("-fexperimental-modules-reduced-bmi");
+ CmdArgs.push_back("-fmodules-reduced-bmi");
if (Args.hasArg(options::OPT_fmodule_output_EQ))
Args.AddLastArg(CmdArgs, options::OPT_fmodule_output_EQ);
@@ -4265,7 +4265,15 @@ static bool RenderModulesOptions(Compilation &C, const Driver &D,
getCXX20NamedModuleOutputPath(Args, Input.getBaseInput())));
}
- // Noop if we see '-fexperimental-modules-reduced-bmi' with other translation
+ if ((Input.getType() == driver::types::TY_CXXModule ||
+ Input.getType() == driver::types::TY_PP_CXXModule) &&
+ (Args.hasArg(options::OPT_fmodule_output) ||
+ Args.hasArg(options::OPT_fmodule_output_EQ) ||
+ Args.hasArg(options::OPT__precompile)) &&
+ !Args.hasArg(options::OPT_modules_reduced_bmi))
+ D.Diag(diag::warn_drv_module_reduced_bmi_not_enabled);
+
+ // Noop if we see '-fmodules-reduced-bmi' with other translation
// units than module units. This is more user friendly to allow end uers to
// enable this feature without asking for help from build systems.
Args.ClaimAllArgs(options::OPT_modules_reduced_bmi);
diff --git a/clang/test/Driver/module-fgen-reduced-bmi.cppm b/clang/test/Driver/module-fgen-reduced-bmi.cppm
index 1223189fb49b72..af98684b5f95f9 100644
--- a/clang/test/Driver/module-fgen-reduced-bmi.cppm
+++ b/clang/test/Driver/module-fgen-reduced-bmi.cppm
@@ -29,13 +29,35 @@
//
// RUN: %clang -std=c++20 Hello.cc -fexperimental-modules-reduced-bmi -Wall -Werror \
// RUN: -c -o Hello.o -### 2>&1 | FileCheck Hello.cc
+//
+// RUN: %clang -std=c++20 Hello.cppm -fmodule-output=Hello.pcm \
+// RUN: -fmodules-reduced-bmi -c -o Hello.o -### 2>&1 | FileCheck Hello.cppm
+//
+// RUN: %clang -std=c++20 Hello.cppm \
+// RUN: -fmodules-reduced-bmi -c -o Hello.o -### 2>&1 | \
+// RUN: FileCheck Hello.cppm --check-prefix=CHECK-UNSPECIFIED
+//
+// RUN: %clang -std=c++20 Hello.cppm \
+// RUN: -fmodules-reduced-bmi -c -### 2>&1 | \
+// RUN: FileCheck Hello.cppm --check-prefix=CHECK-NO-O
+//
+// RUN: %clang -std=c++20 Hello.cppm \
+// RUN: -fmodules-reduced-bmi -c -o AnotherName.o -### 2>&1 | \
+// RUN: FileCheck Hello.cppm --check-prefix=CHECK-ANOTHER-NAME
+//
+// RUN: %clang -std=c++20 Hello.cppm --precompile -fmodules-reduced-bmi \
+// RUN: -o Hello.full.pcm -### 2>&1 | FileCheck Hello.cppm \
+// RUN: --check-prefix=CHECK-EMIT-MODULE-INTERFACE
+//
+// RUN: %clang -std=c++20 Hello.cc -fmodules-reduced-bmi -Wall -Werror \
+// RUN: -c -o Hello.o -### 2>&1 | FileCheck Hello.cc
//--- Hello.cppm
export module Hello;
// Test that we won't generate the emit-module-interface as 2 phase compilation model.
// CHECK-NOT: -emit-module-interface
-// CHECK: "-fexperimental-modules-reduced-bmi"
+// CHECK: "-fmodules-reduced-bmi"
// CHECK-UNSPECIFIED: -fmodule-output=Hello.pcm
@@ -48,4 +70,4 @@ export module Hello;
//--- Hello.cc
-// CHECK-NOT: "-fexperimental-modules-reduced-bmi"
+// CHECK-NOT: "-fmodules-reduced-bmi"
>From a3f9aca79178b58d614c65b6b67b28fc30c6486e Mon Sep 17 00:00:00 2001
From: Chuanqi Xu <yedeng.yd at linux.alibaba.com>
Date: Mon, 4 Nov 2024 10:44:03 +0800
Subject: [PATCH 2/3] Address comments
---
clang/docs/ReleaseNotes.rst | 4 ++++
clang/include/clang/Basic/DiagnosticDriverKinds.td | 9 ++++-----
clang/test/Driver/module-fgen-reduced-bmi.cppm | 8 ++++++++
3 files changed, 16 insertions(+), 5 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 145786bcc59b45..e73fe5cb837bee 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -327,6 +327,10 @@ Modified Compiler Flags
``memset`` and similar functions for which it is a documented undefined
behavior.
+- Added ``-fmodules-reduced-bmi`` flags corresponding to
+ ``-fexperimental-modules-reduced-bmi`` flag and emit warning for not emitting
+ reduced BMI.
+
Removed Compiler Flags
-------------------------
diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index 7589c6f52419dd..99f93e3b73b7bb 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -557,11 +557,10 @@ def err_drv_module_output_with_multiple_arch : Error<
"option '-fmodule-output' can't be used with multiple arch options">;
def warn_drv_module_reduced_bmi_not_enabled : Warning<
- "reduced BMI is expected to be enabled by default in Clang 21. It is encouraged to "
- "enable it ahead of time to avoid potential breaking change. You can enable it "
- "by offering '-fmodules-reduced-bmi' option in one phase compilation model (e.g., CMake). "
- "Or if your build system support two phase compilation model, please contact the "
- "build system authors to support reduced BMI and turn off the warning temporarily">,
+ "reduced BMI is expected to be enabled by default in Clang 21; it can be enabled "
+ "explicitly by passing '-fmodules-reduced-bmi' (in one-phase compilation models, "
+ "like CMake) or by disabling the diagnostic and requesting the build system vendor "
+ "support reduced BMIs (in two-phase compilation models)">,
InGroup<DiagGroup<"missing-reduced-bmi">>;
def warn_drv_delayed_template_parsing_after_cxx20 : Warning<
diff --git a/clang/test/Driver/module-fgen-reduced-bmi.cppm b/clang/test/Driver/module-fgen-reduced-bmi.cppm
index af98684b5f95f9..a2606381483f88 100644
--- a/clang/test/Driver/module-fgen-reduced-bmi.cppm
+++ b/clang/test/Driver/module-fgen-reduced-bmi.cppm
@@ -51,6 +51,12 @@
//
// RUN: %clang -std=c++20 Hello.cc -fmodules-reduced-bmi -Wall -Werror \
// RUN: -c -o Hello.o -### 2>&1 | FileCheck Hello.cc
+//
+// RUN: %clang -std=c++20 Hello.cppm -fmodule-output=Hello.pcm -c -o Hello.o \
+// RUN: -### 2>&1 | FileCheck Hello.cppm -check-prefix=WARN
+//
+// RUN: %clang -std=c++20 Hello.cppm --precompile -o Hello.pcm \
+// RUN: -### 2>&1 | FileCheck Hello.cppm -check-prefix=WARN
//--- Hello.cppm
export module Hello;
@@ -68,6 +74,8 @@ export module Hello;
// flag.
// CHECK-EMIT-MODULE-INTERFACE: -emit-module-interface
+// WARN: reduced BMI is expected to be enabled by default in Clang 21;
+
//--- Hello.cc
// CHECK-NOT: "-fmodules-reduced-bmi"
>From a0168954d07147f03b63d9af5b619e55f05ca002 Mon Sep 17 00:00:00 2001
From: Chuanqi Xu <yedeng.yd at linux.alibaba.com>
Date: Tue, 5 Nov 2024 16:18:58 +0800
Subject: [PATCH 3/3] Update
---
clang/docs/StandardCPlusPlusModules.rst | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/clang/docs/StandardCPlusPlusModules.rst b/clang/docs/StandardCPlusPlusModules.rst
index 26b29337ce42cb..93edce0cf90b76 100644
--- a/clang/docs/StandardCPlusPlusModules.rst
+++ b/clang/docs/StandardCPlusPlusModules.rst
@@ -691,11 +691,10 @@ ensure it is reachable, e.g. ``using N::g;``.
Support for Reduced BMIs is still experimental, but it may become the default
in the future. The expected roadmap for Reduced BMIs as of Clang 19.x is:
-1. ``-fmodules-reduced-bmi`` is opt-in for 1~2 releases. The period depends
+1. ``-fexperimental-modules-reduced-bmi`` was introduced in v19.x
+2. For v20.x, ``-fmodules-reduced-bmi`` is introduced as an equivalent non-experimental
+ option. It is expected to stay opt-in for 1~2 releases, though the period depends
on user feedback and may be extended.
-2. Announce that Reduced BMIs are no longer experimental and introduce
- ``-fmodules-reduced-bmi`` as a new option, and recommend use of the new
- option. This transition is expected to take 1~2 additional releases as well.
3. Finally, ``-fmodules-reduced-bmi`` will be the default. When that time
comes, the term BMI will refer to the Reduced BMI and the Full BMI will only
be meaningful to build systems which elect to support two-phase compilation.
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