libcxx: Add size optimizations

Changed standard to 2a. 2a (as well as 17) contain more constexpr
functions, which are evaluated at compile time. This saves space.

Added --gc-sections. With the CXXABI change, this now makes the package
smaller.

With these, size went down to 210845 on mipsel_24kc.

Also fixed two small compiler warnings. No real change in behavior.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
This commit is contained in:
Rosen Penev 2019-12-31 19:37:35 -08:00 committed by Jo-Philipp Wich
parent 1f8ab1c640
commit 9f7d36d1a9
3 changed files with 39 additions and 1 deletions

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@ -47,7 +47,7 @@ CMAKE_OPTIONS += \
-DLIBCXX_HAS_MUSL_LIBC=$(if $(CONFIG_USE_MUSL),ON,OFF)
TARGET_CXXFLAGS += -D_LIBCPP_DISABLE_DEPRECATION_WARNINGS -Wno-attributes -flto
TARGET_LDFLAGS += -Wl,--as-needed
TARGET_LDFLAGS += -Wl,--gc-sections,--as-needed -flto=jobserver
define Build/InstallDev
$(call Build/InstallDev/cmake,$(1))

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@ -0,0 +1,14 @@
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -524,9 +524,9 @@ remove_flags(-Wno-pedantic -pedantic-errors -pedantic)
if (LIBCXX_HAS_MUSL_LIBC OR LIBCXX_TARGETING_CLANG_CL)
# musl's pthread implementations uses volatile types in their structs which is
# not a constexpr in C++11 but is in C++14, so we use C++14 with musl.
- set(LIBCXX_STANDARD_VER c++14 CACHE STRING "internal option to change build dialect")
+ set(LIBCXX_STANDARD_VER c++2a CACHE STRING "internal option to change build dialect")
else()
- set(LIBCXX_STANDARD_VER c++11 CACHE STRING "internal option to change build dialect")
+ set(LIBCXX_STANDARD_VER c++2a CACHE STRING "internal option to change build dialect")
endif()
add_compile_flags_if_supported(-std=${LIBCXX_STANDARD_VER})
add_compile_flags_if_supported("/std:${LIBCXX_STANDARD_VER}")

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@ -0,0 +1,24 @@
--- a/include/memory
+++ b/include/memory
@@ -1696,7 +1696,7 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits
ptrdiff_t _Np = __end1 - __begin1;
__end2 -= _Np;
if (_Np > 0)
- _VSTD::memcpy(__end2, __begin1, _Np * sizeof(_Tp));
+ __end2 = __begin1;
}
private:
--- a/src/filesystem/filesystem_common.h
+++ b/src/filesystem/filesystem_common.h
@@ -197,8 +197,8 @@ private:
using chrono::duration;
using chrono::duration_cast;
-using TimeSpec = struct ::timespec;
-using StatT = struct ::stat;
+using TimeSpec = struct timespec;
+using StatT = struct stat;
template <class FileTimeT, class TimeT,
bool IsFloat = is_floating_point<typename FileTimeT::rep>::value>