On Fri, 15 Aug 2025 14:18:57 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 > > Fei Gao has updated the pull request with a new target base due to a merge or > a rebase. The incremental webrev excludes the unrelated changes brought in by > the merge/rebase. The pull request contains three additional commits since > the last revision: > > - Add flag in debug builds and nothing in release builds > - Merge branch 'master' into switch-pattern-to-zero > - 8365312: __builtin_clear_padding not supported for variable length > aggregates > > `-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
Looks good. ------------- Marked as reviewed by kbarrett (Reviewer). PR Review: https://git.openjdk.org/jdk/pull/26755#pullrequestreview-3125356783
