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feat(cmake): optional ENABLE_LTO (IPO) for release packaging #9

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Apr 27, 2026
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feat(cmake): optional ENABLE_LTO (IPO) for release packaging #9

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5 changes: 5 additions & 0 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,8 @@ LEG_BUNDLED_LIB(FREETYPE Freetype2 "BUILD_CLIENT AND FEATURE_FREETYPE")
LEG_BUNDLED_LIB(SQLITE3 SQlite3 "BUILD_CLIENT OR BUILD_MOD")
LEG_BUNDLED_LIB(CJSON cJSON "BUILD_ENGINE OR BUILD_MOD")

option(ENABLE_LTO "Enable IPO/LTO for Release-style builds (toolchain must support it)" OFF)

#-----------------------------------------------------------------
# Setup
#-----------------------------------------------------------------
Expand Down Expand Up @@ -174,6 +176,9 @@ include(cmake/ETLTargets.cmake)
# Platform specific compiler settings
include(cmake/ETLPlatform.cmake)

# Optional LTO (after compiler flags are established)
include(cmake/ETLLTO.cmake)

# Source globs
include(cmake/ETLSources.cmake)

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10 changes: 10 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -151,6 +151,16 @@ make
sudo make install # optional; set install vars first
```

**Release packaging — optional LTO**

For **Release** / **RelWithDebInfo** / **MinSizeRel**, you can enable **link-time optimization** if your toolchain supports it (CMake IPO):

```sh
cmake -DENABLE_LTO=ON ..
```

Leave it **off** for normal development (faster links). It cannot be combined with **`ENABLE_ASAN`**.

**Notes**

- 32-bit builds may need **multilib / `-devel`** packages.
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32 changes: 32 additions & 0 deletions cmake/ETLLTO.cmake
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@@ -0,0 +1,32 @@
#-----------------------------------------------------------------
# Optional link-time optimization (IPO / LTO)
#-----------------------------------------------------------------
#
# Off by default: LTO increases link time and needs a capable toolchain.
# When enabled, applies to Release-style configurations only.

if(NOT ENABLE_LTO)
return()
endif()

if(ENABLE_ASAN)
message(FATAL_ERROR "ENABLE_LTO cannot be used together with ENABLE_ASAN.")
endif()

if(CMAKE_VERSION VERSION_LESS "3.9")
message(FATAL_ERROR "ENABLE_LTO requires CMake 3.9 or newer (CheckIPOSupported).")
endif()

include(CheckIPOSupported)
check_ipo_supported(RESULT _etl_ipo_supported OUTPUT _etl_ipo_error)

if(NOT _etl_ipo_supported)
message(WARNING "ENABLE_LTO=ON but IPO is not supported by this toolchain: ${_etl_ipo_error}")
return()
endif()

set(CMAKE_INTERPROCEDURAL_OPTIMIZATION_RELEASE ON)
set(CMAKE_INTERPROCEDURAL_OPTIMIZATION_RELWITHDEBINFO ON)
set(CMAKE_INTERPROCEDURAL_OPTIMIZATION_MINSIZEREL ON)

message(STATUS "Link-time optimization (IPO/LTO) enabled for Release, RelWithDebInfo, MinSizeRel")
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