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feat(build): support LTO in the build system v2 (cmakev2)

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Mirror the link-time optimization support into the cmakev2 build system so
that both build systems behave identically.

- project.cmake (__init_project_configuration): emit -flto=auto as a link
  option when CONFIG_COMPILER_LTO_LINKTIME is set, except for bootloader and
  ESP-TEE builds, otherwise keep -fno-lto.

- build.cmake (idf_build_library): when CONFIG_COMPILER_LTO_COMPILETIME is set,
  compile each linked component with -flto=auto unless it has linker fragments,
  is placed by another component's fragment (see tools/cmake/lto.cmake), has
  opted out via NO_LTO, or is not a static library.

- project.cmake: when CONFIG_APP_REPRODUCIBLE_BUILD is also enabled, apply
  the same three flags as the legacy build system to keep LTO output
  reproducible: pass the prefix-map options to the linker (so link-time code
  generation remaps DW_AT_comp_dir), add -save-temps (stable LTRANS object
  names instead of random $TMPDIR paths in the .map), and pin -frandom-seed
  (byte-identical LTO GIMPLE bytecode). See the commit message of
  "feat(build): add options to enable link-time optimization (LTO)" for the
  full analysis.

The gcc-ar / gcc-ranlib selection and the NO_LTO component property are shared
with the legacy build system through tools/cmake/toolchain.cmake and the common
component registration code, so no cmakev2-specific changes are needed there.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Ivan Grokhotkov (bot)
2026-07-14 19:32:19 +02:00
co-authored by Claude Opus 4.8
parent d20a986999
commit 493a770d40
4 changed files with 91 additions and 8 deletions
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components/bootloader/subproject/CMakeLists_v2.txt
+4
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@@ -92,6 +92,10 @@ idf_build_set_property(IDF_COMPONENT_OPTIONAL_REQUIRES_MODE DEFERRED)
# (CONFIG_BOOTLOADER_COMPILER_OPTIMIZATION_*) set below, not the app-level
# CONFIG_COMPILER_OPTIMIZATION_* defaults.
idf_build_set_property(SET_COMPILER_OPTIMIZATION NO)
# The bootloader relies on linker-script section placement matched by object
# file name, which LTO does not preserve, so it must never be compiled or linked
# with LTO regardless of the application's CONFIG_COMPILER_LTO_* options.
idf_build_set_property(SET_COMPILER_LTO NO)
# Perform internal IDF project initialisation
idf_project_init()