Hi Matt, On Mon, 12 Nov 2018 at 21:26, Matt Turner <matts...@gmail.com> wrote: > > Prior to this patch sizeof(linear_header) was 20 bytes in a > non-debug build on 32-bit platforms. We do some pointer arithmetic to > calculate the next available location with > > ptr = (linear_size_chunk *)((char *)&latest[1] + latest->offset); > > in linear_alloc_child(). The &latest[1] adds 20 bytes, so an allocation > would only be 4-byte aligned. > > On 32-bit SPARC a 'sttw' instruction (which stores a consecutive pair of > 4-byte registers to memory) requires an 8-byte aligned address. Such an > instruction is used to store to an 8-byte integer type, like intmax_t > which is used in glcpp's expression_value_t struct. > > As a result of the 4-byte alignment returned by linear_alloc_child() we > would generate a SIGBUS (unaligned exception) on SPARC. > > According to the GNU libc manual malloc() always returns memory that has > at least an alignment of 8-bytes [1]. I think our allocator should do > the same. > > So, simple fix with two parts: > > (1) Increase SUBALLOC_ALIGNMENT to 8 unconditionally. > (2) Mark linear_header with an aligned attribute, which will cause > its sizeof to be rounded up to that alignment. (We already do > this for ralloc_header) > > With this done, all Mesa's unit tests now pass on SPARC. > > [1] > https://www.gnu.org/software/libc/manual/html_node/Aligned-Memory-Blocks.html > > Fixes: 47e17586924f ("glcpp: use the linear allocator for most objects") > Bug: https://bugs.gentoo.org/636326
This patch didn't apply cleanly on 18.3, so I've resolved the trivial conflict. Fixed patch is at [1] https://cgit.freedesktop.org/mesa/mesa/commit/?h=staging/18.3&id=44dfbdf989956095e1610ce152e838fd9eeb089f Emil _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
