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| author | Lasse Collin <lasse.collin@tukaani.org> | 2024-02-17 21:27:48 +0200 |
|---|---|---|
| committer | Lasse Collin <lasse.collin@tukaani.org> | 2024-02-19 16:28:49 +0200 |
| commit | 4430e075f7ccfc47972d6ca0aa1c3779fc265e10 (patch) | |
| tree | 0e9be5301abd86522a272f7f6a2ccec1f21320d9 | |
| parent | CMake: Handle symbol versioning on MicroBlaze specially. (diff) | |
| download | xz-4430e075f7ccfc47972d6ca0aa1c3779fc265e10.tar.xz | |
CMake: Use -O2 instead of -O3 in CMAKE_BUILD_TYPE=Release.
-O3 doesn't seem useful for speed but it makes the code bigger.
CMake makes is difficult for users to simply override the
optimization level: CFLAGS / CMAKE_C_FLAGS aren't helpful because
they go before CMAKE_C_FLAGS_RELEASE. Of course, users can override
CMAKE_C_FLAGS_RELEASE directly but then they have to remember to
add also -DNDEBUG to disable assertions.
This commit changes -O3 to -O2 in CMAKE_C_FLAGS_RELEASE if and only if
CMAKE_C_FLAGS_RELEASE cache variable doesn't already exist. So if
a custom value is passed on the command line (or reconfiguring an
already-configured build), the cache variable won't be modified.
| -rw-r--r-- | CMakeLists.txt | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/CMakeLists.txt b/CMakeLists.txt index 19ae4814..9716f350 100644 --- a/CMakeLists.txt +++ b/CMakeLists.txt @@ -74,9 +74,28 @@ string(REGEX REPLACE .*$" "\\1.\\2.\\3" PACKAGE_VERSION "${PACKAGE_VERSION}") +# With several compilers, CMAKE_BUILD_TYPE=Release uses -O3 optimization +# which results in bigger code without a clear difference in speed. If +# no user-defined CMAKE_C_FLAGS_RELEASE is present, override -O3 to -O2 +# to make it possible to recommend CMAKE_BUILD_TYPE=Release. +if(NOT DEFINED CMAKE_C_FLAGS_RELEASE) + set(OVERRIDE_O3_IN_C_FLAGS_RELEASE ON) +endif() + # Among other things, this gives us variables xz_VERSION and xz_VERSION_MAJOR. project(xz VERSION "${PACKAGE_VERSION}" LANGUAGES C) +if(OVERRIDE_O3_IN_C_FLAGS_RELEASE) + # Looking at CMake's source, there aren't any _FLAGS_RELEASE_INIT + # entries where "-O3" would appear as part of some other option, + # thus a simple search and replace should be fine. + string(REPLACE -O3 -O2 CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE}") + + # Update the cache value while keeping its docstring unchanged. + set_property(CACHE CMAKE_C_FLAGS_RELEASE + PROPERTY VALUE "${CMAKE_C_FLAGS_RELEASE}") +endif() + # We need a compiler that supports enough C99 or newer (variable-length arrays # aren't needed, those are optional in C17). Setting CMAKE_C_STANDARD here # makes it the default for all targets. It doesn't affect the INTERFACE so |