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Frantisek Hrbata
e4fa15b50a
Profiling shows that parsing the linker fragment (.lf) files with
pyparsing is the single largest cost in ldgen (~58% of total runtime).
parse_fragment_file() rebuilds its grammar from scratch on every call
because the conditional parser closure has to capture sdkconfig to
evaluate if/elif/else at parse time.
Add a cache that pickles the parsed FragmentFile object list to
<output>.lfcache. The cache is keyed on fragment file paths+mtimes
plus sdkconfig and kconfig mtimes — sdkconfig is included because
fragment if/elif/else blocks are evaluated against it at parse time.
This avoids the pyparsing cost on rebuilds where ldgen has to run
but the fragment files themselves are unchanged — for example when
a function is added or removed in a source file. Cache hits produce
the same sections.ld as a full parse, and any pickle load failure
falls through to a normal parse, so cache corruption or a Python
upgrade cannot produce a wrong build.
Print "Skipping linker fragment parsing, fragment files unchanged"
on the lf cache hit path so build logs show when the optimization
fired — this makes it easy to diagnose user reports of unexpected
ldgen behavior.
The LDGEN_NO_CACHE environment variable disables the lf cache. When
set, ldgen falls through to a normal parse without consulting or
writing the cache file.
Measured on wifi_station (205 libs, 67 .lf files), median of 10 runs:
before after
rebuild, section change, .lf unchanged 5.82s 1.34s
Signed-off-by: Frantisek Hrbata <frantisek.hrbata@espressif.com>