feat(profile): vernier wrapper modes + .vernier.json analyzer

[ryanseys]

deleted.

[gemini-code-assist]

Code Review

This pull request introduces a profiling suite for spinel_codegen.rb, including a Makefile integration, a Vernier wrapper script, and a profile analyzer that generates markdown reports. The reviewer identified several issues, such as potential crashes in CLI argument parsing due to missing bounds checks, an unused variable in a performance-sensitive loop, and a brittle method for extracting help text from the source file.

[gemini-code-assist]

The seen hash is initialized and populated but never read within the jsAllocations accumulation loop. Since this loop processes every allocation sample, removing the unused hash will slightly improve performance and clarity in this hot path.

    leaf = true
    walk_stack(stack_idx, stack_prefix, stack_frame, frame_func) do |fi|
      func_data[fi][:alloc] += weight if leaf
      leaf = false
    end

[gemini-code-assist]

The --diff argument parsing does not verify that two paths are actually provided. If --diff is the last argument or only followed by one path, argv[i + 1] or argv[i + 2] will be nil, causing a crash in load_profile (specifically at path.end_with?). Consider adding a check for the number of remaining arguments.

[gemini-code-assist]

Extracting the help text by hardcoded line numbers (lines[1..14]) is brittle. Any changes to the file header or the addition of comments at the top of the file will break the help output. Using a heredoc is a more robust way to define the help text.

      puts <<~HELP
        Programmatic analyzer for Vernier .vernier.json[.gz] profiles
        (Firefox Profiler format). Emits a markdown report with the top
        functions by self time, total time, allocation count, and (in
        retained mode) retained bytes -- no profiler.firefox.com required.

        Usage:
          ruby bin/analyze_profile.rb path/to/profile.vernier.json [--out report.md]
          ruby bin/analyze_profile.rb --diff baseline.json after.json [--out diff.md]

        Pure stdlib (json + zlib). No external gems.
      HELP

[gemini-code-assist]

The script lacks bounds checking when accessing ARGV[i + 1] for numeric options like --interval and --alloc. If these flags are provided without a following value, Integer(nil) will be called, raising a TypeError and crashing the script.