ping?
On 20 September 2017 at 15:17, Christophe Lyon <christophe.l...@linaro.org> wrote: > Hi, > > On 11 September 2017 at 10:45, Andrew Pinski <pins...@gmail.com> wrote: >> On Tue, Jul 18, 2017 at 5:50 AM, Christophe Lyon >> <christophe.l...@linaro.org> wrote: >>> Hello, >>> >>> I've received a complaint that GCC for AArch64 would generate >>> vectorized code relying on unaligned memory accesses even when using >>> -mstrict-align. This is a problem for code where such accesses lead to >>> memory faults. >>> >>> A previous patch (r243333) introduced >>> aarch64_builtin_support_vector_misalignment, which rejects such >>> accesses when the element size is 64 bits, and accept them otherwise, >>> which I think it shouldn't. The testcase added at that time only used >>> 64 bits elements, and therefore didn't fully test the patch. >>> >>> The report I received is about vectorized accesses to an array of >>> unsigned chars, whose start address is not aligned on a 128 bits >>> boundary. >>> >>> The attached patch fixes the problem by making >>> aarch64_builtin_support_vector_misalignment always return false when >>> the misalignment is not known at compile time. >>> >>> I've also added a testcase, which tries to check if the array start >>> address alignment is checked (using %16, and-ing with #15), so that >>> loop peeling is performed *before* using vectorized accesses. Without >>> the patch, vectorized accesses are used at the beginning of the array, >>> and byte accesses are used for the remainder at the end, and there is >>> not such 'and wX,wX,15'. >>> >>> BTW, I'm not sure about the same hook for arm... it seems to me it has >>> a similar problem. >>> >>> OK? >> >> I would keep part of the comment: >> - /* Misalignment factor is unknown at compile time but we know >> - it's word aligned. */ >> >> Something like: >> /* Misalignment factor is unknown at compile time. */ >> >> Otherwise it is not obvious what -1 means. >> >> Other than I think this patch is good (I cannot approve though). >> > > Here is an updated patch, with the comment added as Andrew suggested. > > OK? > > Thanks, > > Christophe > >> Thanks, >> Andrew >> >>> >>> Thanks, >>> >>> Christophe
