Chandler Carruth 523e1c2972 Add a native Bazel build for libpfm and use it in benchmarks. (#3601) ...

The `libpfm` in the Bazel central repository uses `make` to build it,
which is difficult to integrate with our toolchain. Rather than try to
fix all the issues there, it's easy to just add a native Bazel build for
the library. I don't know that any of the relevant upstream folks are
interested in this kind of build, but it seems easy for us to maintain
as a Carbon project build configuration. I've also not tried to port all
of the different configurations as a consequence, and only 64-bit x86
and Arm as that seems the only likely architectures we'll care about in
the near term.

I've kept this using the `bzlmod` stuff as best I can, and I *think* I'm
holding all of those pieces correctly, but if not, happy for suggestions
on adjustments.

The `google_benchmark` package also has an awkward way of enabling
`libpfm` support using a top-level `bazel` command line flag. I think
this is because of how brittle the Bazel build of `libpfm` is, but I'm
not sure. With the new build, it seems easy to patch `google_benchmark`
to detect the same conditions as we build `libpfm` under, and enable it
there. So I've done this to avoid folks having to pass a command line
flag on platforms where it is supported.

The result is that we now get really nice CPU counter support in our
benchmarks out-of-the-box on Linux x86-64 and AArch64. For example on my
Fedora Asahi install on a Mac Mini I get:

```console
$ bazel run -c opt --copt=-gmlt //common:hashing_benchmark --run_under="taskset -c 4" -- --benchmark_counters_tabular=true --benchmark_perf_counters=CYCLES,INSTRUCTIONS
INFO: Invocation ID: 4aaeb9e9-7df5-4f1f-b56b-c03411790268
INFO: Analyzed target //common:hashing_benchmark (0 packages loaded, 0 targets configured).
INFO: Found 1 target...
Target //common:hashing_benchmark up-to-date:
  bazel-bin/common/hashing_benchmark
INFO: Elapsed time: 0.360s, Critical Path: 0.02s
INFO: 1 process: 1 internal.
INFO: Build completed successfully, 1 total action
INFO: Running command line: /bin/bash -c 'taskset -c 4 bazel-bin/common/hashing_benchmark '\''--benchmark_counters_tabular=true'\'' '\''--benchmark_perf_counters=CYCLES,INSTRUCTIONS'\'''
2024-01-15T00:10:50-08:00
Running /home/chandlerc/.cache/bazel/_bazel_chandlerc/b686aa8910e0845b88c21d715819b076/execroot/_main/bazel-out/aarch64-opt/bin/common/hashing_benchmark
Run on (8 X 2064 MHz CPU s)
CPU Caches:
  L1 Data 64 KiB (x8)
  L1 Instruction 128 KiB (x8)
  L2 Unified 4096 KiB (x2)
Load Average: 0.01, 0.08, 0.08
--------------------------------------------------------------------------------------------------------------------------------------------------------------
Benchmark                                                                           Time             CPU   Iterations     CYCLES INSTRUCTIONS bytes_per_second
--------------------------------------------------------------------------------------------------------------------------------------------------------------
BM_LatencyHash<RandValues<uint8_t>, CarbonHashBench>                             4.11 ns         4.11 ns    170200064    13.1321      9.00587      232.116Mi/s
BM_LatencyHash<RandValues<uint8_t>, AbseilHashBench>                             4.82 ns         4.82 ns    145643520    15.3657      12.0059      197.946Mi/s
BM_LatencyHash<RandValues<uint8_t>, LLVMHashBench>                               7.96 ns         7.95 ns     87956480    25.3737      17.0068      119.991Mi/s
BM_LatencyHash<RandValues<uint16_t>, CarbonHashBench>                            4.11 ns         4.11 ns    170365952    13.1247      9.00587      464.573Mi/s
BM_LatencyHash<RandValues<uint16_t>, AbseilHashBench>                            5.51 ns         5.51 ns    127568896    17.5578      14.0059      346.225Mi/s
BM_LatencyHash<RandValues<uint16_t>, LLVMHashBench>                              8.00 ns         7.99 ns     87085056     25.377      17.0068      238.834Mi/s
BM_LatencyHash<RandValues<std::pair<uint8_t, uint8_t>>, CarbonHashBench>         4.91 ns         4.90 ns    136013824    15.6456      14.0059      389.006Mi/s
BM_LatencyHash<RandValues<std::pair<uint8_t, uint8_t>>, AbseilHashBench>         6.85 ns         6.85 ns    102630400    21.8041      18.0059      278.637Mi/s
BM_LatencyHash<RandValues<std::pair<uint8_t, uint8_t>>, LLVMHashBench>           7.57 ns         7.56 ns     92798976    24.1437      20.0068      252.151Mi/s
BM_LatencyHash<RandValues<uint32_t>, CarbonHashBench>                            4.12 ns         4.12 ns    170229760    13.1272      9.00587      926.444Mi/s
BM_LatencyHash<RandValues<uint32_t>, AbseilHashBench>                            4.93 ns         4.92 ns    145304576    15.3738      12.0059      775.224Mi/s
BM_LatencyHash<RandValues<uint32_t>, LLVMHashBench>                              8.11 ns         8.10 ns     87127040     25.373      17.0068       470.98Mi/s
```

2024-01-17 03:39:01 +00:00

..

0001-Introduce-a-simple-native-Bazel-build.patch

Add a native Bazel build for libpfm and use it in benchmarks. (#3601)

2024-01-17 03:39:01 +00:00

BUILD

Add a native Bazel build for libpfm and use it in benchmarks. (#3601)

2024-01-17 03:39:01 +00:00