================ @@ -216,51 +198,56 @@ We explain the options in the following sections. How to enable standard C++ modules ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Currently, standard C++ modules are enabled automatically -if the language standard is ``-std=c++20`` or newer. +Standard C++ modules are enabled automatically if the language standard is +``-std=c++20`` or newer. How to produce a BMI ~~~~~~~~~~~~~~~~~~~~ -We can generate a BMI for an importable module unit by either ``--precompile`` -or ``-fmodule-output`` flags. +To generate a BMI for an importable module unit, use either the ``--precompile`` +or ``-fmodule-output`` command line option. -The ``--precompile`` option generates the BMI as the output of the compilation and the output path -can be specified using the ``-o`` option. +The ``--precompile`` option generates the BMI as the output of the compilation +and the output path can be specified using the ``-o`` option. -The ``-fmodule-output`` option generates the BMI as a by-product of the compilation. -If ``-fmodule-output=`` is specified, the BMI will be emitted the specified location. Then if -``-fmodule-output`` and ``-c`` are specified, the BMI will be emitted in the directory of the -output file with the name of the input file with the new extension ``.pcm``. Otherwise, the BMI -will be emitted in the working directory with the name of the input file with the new extension +The ``-fmodule-output`` option generates the BMI as a by-product of the +compilation. If ``-fmodule-output=`` is specified, the BMI will be emitted to +the specified location. If ``-fmodule-output`` and ``-c`` are specified, the +BMI will be emitted in the directory of the output file with the name of the +input file with the extension ``.pcm``. Otherwise, the BMI will be emitted in +the working directory with the name of the input file with the extension ``.pcm``. -The style to generate BMIs by ``--precompile`` is called two-phase compilation since it takes -2 steps to compile a source file to an object file. The style to generate BMIs by ``-fmodule-output`` -is called one-phase compilation respectively. The one-phase compilation model is simpler -for build systems to implement and the two-phase compilation has the potential to compile faster due -to higher parallelism. As an example, if there are two module units A and B, and B depends on A, the -one-phase compilation model would need to compile them serially, whereas the two-phase compilation -model may be able to compile them simultaneously if the compilation from A.pcm to A.o takes a long -time. - -File name requirement -~~~~~~~~~~~~~~~~~~~~~ +Generating BMIs with ``--precompile`` is called two-phase compilation because +it takes two steps to compile a source file to an object file. Generating BMIs +with ``-fmodule-output`` is called one-phase compilation. The one-phase +compilation model is simpler for build systems to implement and the two-phase +compilation has the potential to compile faster due to higher parallelism. As +an example, if there are two module units ``A`` and ``B``, and ``B`` depends on +``A``, the one-phase compilation model needs to compile them serially, whereas +the two-phase compilation model may be able to compile them simultaneously if ---------------- erichkeane wrote:
```suggestion the two-phase compilation model is able to be compiled as soon as ``A.pcm`` is available, and thus can be compiled simultaneously as the ``A.pcm`` to ``A.o`` compilation step. ``` https://github.com/llvm/llvm-project/pull/90237 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
