v4 updates 1. Make use of HWCAP2_LSE128, as defined in the Linux kernel v6.7 for feature check. This has required adding a new patch to the series, enabling ifunc resolvers to read a second arg of type `__ifunc_arg_t *', from which the `_hwcap2' member can be queried for LSE128 support. HWCAP2_LSE128, HWCAP_ATOMICS and __ifunc_arg_t are conditionally defined in the `host-config.h' file to allow backwards compatibility with older versions of glibc which lack definitions for these.
2. Run configure test LIBAT_TEST_FEAT_LSE128 unconditionally, renaming it to LIBAT_TEST_FEAT_AARCH64_LSE128. While it may seem counter-intuitive to run an aarch64 test on non-aarch64 targets, the Automake manual makes it clear: "Note that you must arrange for every AM_CONDITIONAL to be invoked every time configure is run. If AM_CONDITIONAL is run conditionally (e.g., in a shell if statement), then the result will confuse automake." Failure to do so has been found to result in Libatomic build failures on arm and x86_64 targets. 3. Minor changes in the implementations of {ENTRY|END}_FEAT and ALIAS macros used in `config/linux/aarch64/atomic_16.S' 4. Improve commit message in PATCH 2/3 documenting design choice around merging REL and ACQ_REL memory orderings in LSE128 atomic functions. Regression-tested on aarch64-none-linux-gnu on Cortex-A72 and LSE128-enabled Armv-A Base RevC AEM FVP. --- Building upon Wilco Dijkstra's work on AArch64 128-bit atomics for Libatomic, namely the patches from [1] and [2], this patch series extends the library's capabilities to dynamically select and emit Armv9.4-a LSE128 implementations of atomic operations via ifuncs at run-time whenever architectural support is present. Regression tested on aarch64-linux-gnu target with LSE128-support. [1] https://gcc.gnu.org/pipermail/gcc-patches/2023-June/620529.html [2] https://gcc.gnu.org/pipermail/gcc-patches/2023-August/626358.html Victor Do Nascimento (4): libatomic: atomic_16.S: Improve ENTRY, END and ALIAS macro interface libatomic: Add support for __ifunc_arg_t arg in ifunc resolver libatomic: Enable LSE128 128-bit atomics for armv9.4-a aarch64: Add explicit checks for implicit LSE/LSE2 requirements. libatomic/Makefile.am | 3 + libatomic/Makefile.in | 1 + libatomic/acinclude.m4 | 19 ++ libatomic/auto-config.h.in | 3 + libatomic/config/linux/aarch64/atomic_16.S | 247 ++++++++++++++++--- libatomic/config/linux/aarch64/host-config.h | 60 ++++- libatomic/configure | 61 ++++- libatomic/configure.ac | 3 + libatomic/configure.tgt | 2 +- 9 files changed, 358 insertions(+), 41 deletions(-) -- 2.42.0