On Wed, 13 Aug 2025 09:16:15 GMT, Fei Gao <f...@openjdk.org> wrote: > `-ftrivial-auto-var-init=pattern` [1] supported by gcc-12 was added recently > to help detect uses of uninitialized memory. [2] Under this extension mode, > `__builtin_clear_padding` is called to clear the padding bits in object > representation. But the builtin function does not support variable length > aggregates [3]. > > `vfloat2_sve_sleef` is a typedef of `svfloat32x2_t`, which is defined as an > opaque sizeless type in ARM C Language Extensions (ACLE) [4]. When > `__builtin_clear_padding` is applied to such a type, it triggers the > unsupported code path and results in build failures when compiling libsleef > on Linux-AArch64, as reported in JDK-8364185 [5]. > > Switching the initialization mode with gcc-12 from `pattern` to `zero` avoids > the use of this unsupported `__builtin_clear_padding` and resolves the issue. > > I did not encounter similar problems when building with Clang-16 [6]. > > This patch changes the initialization mode from `pattern` to `zero` when > compiling libsleef SVE component on Linux-AArch64 with gcc-12 to fix the > build failure and help avoid potential security issues related to > uninitialized padding > > Testing (combined with https://github.com/openjdk/jdk/pull/26577): > 1. Release and fastdebug build with gcc-11, gcc-12, and clang-16 > 2. `test/jdk/jdk/incubator/vector` passed on both 256-bit SVE and NEON > machines > > [1] > https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Optimize-Options.html#index-ftrivial-auto-var-init > [2] > https://github.com/openjdk/jdk/commit/fae37aaae8b36fd74309b84fa1fdf017c7d932ed > [3] https://gcc.gnu.org/pipermail/gcc-patches/2020-November/559214.html > [4] https://arm-software.github.io/acle/main/acle.html#arm_sveh > [5] https://bugs.openjdk.org/browse/JDK-8364185 > [6] https://releases.llvm.org/16.0.0/tools/clang/docs/ReleaseNotes.html
This pull request has now been integrated. Changeset: 999761d0 Author: Fei Gao <f...@openjdk.org> URL: https://git.openjdk.org/jdk/commit/999761d0f6d37c9cd6ec482620800b694c5fb9ad Stats: 11 lines in 1 file changed: 11 ins; 0 del; 0 mod 8365312: GCC 12 cannot compile SVE on aarch64 with auto-var-init pattern Reviewed-by: kbarrett, ihse, erikj ------------- PR: https://git.openjdk.org/jdk/pull/26755
