On Thu, Feb 27, 2025 at 05:52:17PM -0800, Andre Muezerie wrote: > This patchset allows users to specify the CPU for which the generated > code should be optimized for by passing the CPU name. > > MSVC does not provide this functionality natively, so logic was > added. This additional logic relies on a table which stores instruction > set availability (like AXV512F) for different CPUs. > To make it easier to update this table a new devtool is introduced > with this patch. The new tool generates the table entries for all CPUs > listed in an input file using a recent version of the compiler, which > has all the information needed. This reduces enormously the amount > of work needed to update the table in msvc/meson.build and makes the > process much less error prone. > > Signed-off-by: Andre Muezerie <andre...@linux.microsoft.com> > --- > devtools/dump-cpu-flags/README.md | 25 +++++ > devtools/dump-cpu-flags/cpu-names.txt | 120 +++++++++++++++++++++ > devtools/dump-cpu-flags/dump-cpu-flags.cpp | 119 ++++++++++++++++++++ > devtools/dump-cpu-flags/dump-cpu-flags.py | 41 +++++++ > 4 files changed, 305 insertions(+) > create mode 100644 devtools/dump-cpu-flags/README.md > create mode 100644 devtools/dump-cpu-flags/cpu-names.txt > create mode 100644 devtools/dump-cpu-flags/dump-cpu-flags.cpp > create mode 100644 devtools/dump-cpu-flags/dump-cpu-flags.py > > diff --git a/devtools/dump-cpu-flags/README.md > b/devtools/dump-cpu-flags/README.md > new file mode 100644 > index 0000000000..3db69f9f8f > --- /dev/null > +++ b/devtools/dump-cpu-flags/README.md > @@ -0,0 +1,25 @@ > +# Generating updated CPU flags > + > +File `config\x86\msvc\meson.build` has a table with flags indicating > instruction set support for a variety of CPU types. > + > +Script `dump-cpu-flags.py` can be used to generate updated entries for this > table. > + > +The CPU names are stored in file `cpu-names.txt`, which is consumed by > `dump-cpu-flags.py`. The formatting used in that file is described at the top > of the file itself. > + > +The script relies on the information embedded in the g++ compiler. This > means that an updated table can automatically be generated by switching to a > newer version of the compiler. This avoids the need to manually edit the > entries, which is error prone. With the script the table entries can just > copied and pasted into `meson.build`. The only thing that might need to be > done is adding new CPU names to cpu-names.txt, when new CPUs are released. > + > +**NOTE**: CPUs not known to the compiler will result in errors, which can be > ignored (`dump-cpu-flags.py` will ignore these errors and continue). For best > results use the latest g++ compiler available. > + > +Below is a sample output, where an error was logged because the compiler did > not know about a CPU named ‘raptorlake’. > + > +```sh > +$ ./dump-cpu-flags.py > + 'x86-64-v2': [], > + 'x86-64-v3': ['AVX', 'AVX2'], > + 'x86-64-v4': ['AVX', 'AVX2', 'AVX512F', 'AVX512VL', 'AVX512BW', > 'AVX512DQ', 'AVX512CD'], > + 'alderlake': ['AVX', 'PCLMUL', 'RDRND', 'AVX2', 'RDSEED', 'AES', > 'VPCLMULQDQ', 'GFNI'], > +cc1plus: error: bad value (‘raptorlake’) for ‘-march=’ switch > +cc1plus: note: valid arguments to ‘-march=’ switch are: nocona core2 nehalem > corei7 westmere sandybridge... > + 'silvermont': ['PCLMUL', 'RDRND'], > + 'slm': ['PCLMUL', 'RDRND'], > +``` > \ No newline at end of file
How about having the tool output a valid meson.build file, that can then be used directly without copy-paste. While I know such a thing would end up with us having deep subdir structures, it could be just loaded from e.g. config/x86/msvc/cpu-flags/meson.build, for example. /Bruce
