[C++20] [Modules] Convert '-fexperimental-modules-reduced-bmi' to '-fmodules-reduced-bmi' #114382
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
llvmbot
added
clang
|
@llvm/pr-subscribers-libcxx @llvm/pr-subscribers-clang Author: Chuanqi Xu (ChuanqiXu9) ChangesAccording to our previous consensus in https://clang.llvm.org/docs/StandardCPlusPlusModules.html#reduced-bmi, the reduced BMI will be the default and recommend users to use the new option. The This patch literally did the second point in https://clang.llvm.org/docs/StandardCPlusPlusModules.html#reduced-bmi Full diff: https://github.com/llvm/llvm-project/pull/114382.diff 5 Files Affected:
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"
|
|
@llvm/pr-subscribers-clang-modules Author: Chuanqi Xu (ChuanqiXu9) ChangesAccording to our previous consensus in https://clang.llvm.org/docs/StandardCPlusPlusModules.html#reduced-bmi, the reduced BMI will be the default and recommend users to use the new option. The This patch literally did the second point in https://clang.llvm.org/docs/StandardCPlusPlusModules.html#reduced-bmi Full diff: https://github.com/llvm/llvm-project/pull/114382.diff 5 Files Affected:
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"
|
|
@llvm/pr-subscribers-clang-driver Author: Chuanqi Xu (ChuanqiXu9) ChangesAccording to our previous consensus in https://clang.llvm.org/docs/StandardCPlusPlusModules.html#reduced-bmi, the reduced BMI will be the default and recommend users to use the new option. The This patch literally did the second point in https://clang.llvm.org/docs/StandardCPlusPlusModules.html#reduced-bmi Full diff: https://github.com/llvm/llvm-project/pull/114382.diff 5 Files Affected:
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"
|
Comment on lines
560
to
564
| "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">, |
There was a problem hiding this comment.
Suggested change
| "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)">, |
Oof, this is a bit tough -- diagnostics need to be terse and should not contain full sentences. I took a stab at rewording for our usual diagnostic style.
Probably need to re-flow this for 80 col limits
This diagnostic is missing test coverage.
There was a problem hiding this comment.
Done. I feel the new wording is pretty cool and fine enough : )
h-vetinari
reviewed
Nov 2, 2024
| @@ -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: | |||
There was a problem hiding this comment.
Suggested change
| in the future. The expected roadmap for Reduced BMIs as of Clang 19.x is: | |
| in the future. The expected roadmap for Reduced BMIs as of Clang 20.x is: |
There was a problem hiding this comment.
I looked up the dictionary and it says "as of" means "from". So I feel the wording is good since it was added in 19.
There was a problem hiding this comment.
It's confusing to update/clarify the plan during the 20.x cycle and then not update the "as of 19.x" (even though the overall shape of the plan didn't change). If you want to keep the "as of 19.x", then we should specify which steps have been done already (see below), though IMO any updates here should also update the "as of".
h-vetinari
reviewed
Nov 4, 2024
| @@ -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: | |||
There was a problem hiding this comment.
It's confusing to update/clarify the plan during the 20.x cycle and then not update the "as of 19.x" (even though the overall shape of the plan didn't change). If you want to keep the "as of 19.x", then we should specify which steps have been done already (see below), though IMO any updates here should also update the "as of".
Comment on lines
694
to
697
| 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 |
There was a problem hiding this comment.
w.r.t. keeping the "as of 19.x": since removing experimental- prefix was part of the plan since v19, the first point should either be marked as done (or simply removed), but not just renamed (which would be inconsistent both with the "as of 19.x", as well as the following item that already covers the same point). For example:
Suggested change
| 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 | |
| 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. | |
| 3. Finally, [...] |
mizvekov
reviewed
Nov 5, 2024
There was a problem hiding this comment.
I think the overall plan is fine, thanks for working on it!
I think the idea of issuing a warning in order to get users to opt-in to a flag is somewhat novel. Have I missed discussion about this approach, versus simply changing the default?
Regardless, for any new warning we add here, we will probably need to add a targeted way to disable that warning, as otherwise users of Werror are likely to complain.
I originally mentioned it in #85050 and then in the document. And it looks like no one had a question about it.
We can disable it with the same way with other warnings, e.g., |
|
I'd like to land this in the next week if no objection comes in. |
|
If there are more opinions, let's continue it in post commit review. |
ChuanqiXu9
force-pushed
the
ModulesReducedBMI
branch
from
4b8dec4 to
7083728
Compare
llvmbot
added
the
libc++
|
I forgot this affects modules support in libc++. Let's wait for the review from libc++ folks. |
ChuanqiXu9
force-pushed
the
ModulesReducedBMI
branch
from
7083728 to
27ce98f
Compare
|
It looks the CI will compile libc++ with "old" clang19 and the just built clang. So it might not be able to recognize the new flag. Tried to use |
|
I still find the current approach wrt the warning to be odd, we would basically force every modules user to change their command line, either by adding the new I can't recall prior art on this. If we think this has such a high chance of causing breakages, perhaps we shouldn't warn at all. Otherwise, we should just change the default. |
ldionne
reviewed
Dec 6, 2024
libcxx/utils/libcxx/test/format.py
Outdated
| @@ -172,6 +172,7 @@ def parseScript(test, preamble): | |||
| f"{compileFlags} " | |||
| "-Wno-reserved-module-identifier -Wno-reserved-user-defined-literal " | |||
| "-fmodule-file=std=%T/std.pcm " # The std.compat module imports std. | |||
| "-fexperimental-modules-reduced-bmi " | |||
There was a problem hiding this comment.
Is the intent to have people using a -fexperimental-foo flag whenever they compile with C++20 modules enabled?
libcxx/utils/libcxx/test/format.py
Outdated
| @@ -188,6 +189,7 @@ def parseScript(test, preamble): | |||
| "%dbg(MODULE std) %{cxx} %{flags} " | |||
| f"{compileFlags} " | |||
| "-Wno-reserved-module-identifier -Wno-reserved-user-defined-literal " | |||
| "-fexperimental-modules-reduced-bmi " | |||
There was a problem hiding this comment.
If this is the "new way" of building with C++20 modules, then I think it would make sense to mark the offending libc++ tests as UNSUPPORTED: clang-18, clang-19. But that does seem like a big user-facing change too, doesn't it?
There was a problem hiding this comment.
Yeah, so I'd like to accept @mizvekov 's suggestion to not emit the warning to avoid these failures in users code.
Yeah, my intention is to get more users get involved during the cycle to make the final output more stable. But it is not traditional indeed. Given it makes some problems already, let's follow the traditional step in the beginning. |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
According to our previous consensus in https://clang.llvm.org/docs/StandardCPlusPlusModules.html#reduced-bmi, the reduced BMI will be the default and recommend users to use the new option.
The
-fexperimental-modules-reduced-bmioption is introduced in #85050 in Mar13 and released in 19.x. And now we are in 20's release cycle. Also I rarely receive issue reports about reduced BMI. No matter it is due to the quality of reduced BMI is really good or no one uses it. I think we should speed up the process to get more people get involved.This patch literally did the second point in https://clang.llvm.org/docs/StandardCPlusPlusModules.html#reduced-bmi