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fix(cmake): support LTO and Windows section elimination #56

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Merged
gianni-cor merged 1 commit into from
Oct 13, 2026
Merged

fix(cmake): support LTO and Windows section elimination #56

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21 changes: 21 additions & 0 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -101,6 +101,7 @@ option(SD_MUSA "sd: musa backend" OFF)
option(SD_BUILD_SHARED_LIBS "sd: build shared libs" OFF)
option(SD_BUILD_SHARED_GGML_LIB "sd: build ggml as a separate shared lib" OFF)
option(SD_USE_SYSTEM_GGML "sd: use system-installed GGML library" OFF)
option(SD_LTO "sd: enable link time optimization" OFF)
#option(SD_BUILD_SERVER "sd: build server example" ON)

set(CMAKE_C_STANDARD 11)
Expand Down Expand Up @@ -361,6 +362,26 @@ endif()

add_subdirectory(thirdparty)

if(SD_LTO)
include(CheckIPOSupported)
check_ipo_supported(RESULT SD_IPO_SUPPORTED OUTPUT SD_IPO_ERROR LANGUAGES C CXX)
if(NOT SD_IPO_SUPPORTED)
message(FATAL_ERROR "SD_LTO requires IPO support: ${SD_IPO_ERROR}")
endif()
endif()

foreach(SD_TARGET IN ITEMS ${SD_LIB} zip)
if(MSVC)
# Static-library consumers can discard unused code and embedded data.
target_compile_options(${SD_TARGET} PRIVATE
"$<$<OR:$<CONFIG:Release>,$<CONFIG:RelWithDebInfo>,$<CONFIG:MinSizeRel>>:/Gy>"
"$<$<OR:$<CONFIG:Release>,$<CONFIG:RelWithDebInfo>,$<CONFIG:MinSizeRel>>:/Gw>")
endif()
if(SD_LTO)
set_property(TARGET ${SD_TARGET} PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
endif()
endforeach()

target_sources(${SD_LIB} PRIVATE $<TARGET_OBJECTS:zip>)
target_link_libraries(${SD_LIB} PUBLIC ggml)
target_include_directories(${SD_LIB} PUBLIC . src include)
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16 changes: 16 additions & 0 deletions docs/build.md
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Expand Up @@ -43,6 +43,22 @@ vendored builds the in-tree `add_definitions(-DGGML_MAX_NAME=128)` applies.
The GPU backend flags below (`-DSD_METAL=ON`, `-DSD_CUDA=ON`, ...) apply to both
paths.

## Link-time optimization

Pass `-DSD_LTO=ON` to enable CMake's interprocedural optimization for the engine
and its embedded zip object library. With clang-cl this uses ThinLTO; the final
consumer must use a compatible LLVM toolchain (`llvm-lib` and `lld-link`).
Configuration fails if the compiler/linker combination cannot support IPO.

Enable `-DGGML_LTO=ON` when building ggml too. For `SD_USE_SYSTEM_GGML=ON`, that
option belongs in the separate ggml build. Both options default to `OFF`.

Windows release builds package functions and data in individual sections
(`/Gy`, `/Gw`). A consuming DLL or executable can discard unused sections and
fold identical data with `/OPT:REF` and `/OPT:ICF`. In particular, these settings
allow unused and duplicate embedded Vulkan shaders to be removed at the final
link. The library does not change the consumer's exports or optimization level.

## WebP and WebM Support in Examples

The example applications (`examples/cli` and `examples/server`) use `libwebp` to support WebP image I/O, and `examples/cli` can also use `libwebm` for `.webm` video output. Both are enabled by default. WebM output currently reuses `libwebp` to encode each frame as VP8 before muxing with `libwebm`.
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