pratlucas added inline comments.
================ Comment at: clang/lib/CodeGen/CGBuiltin.cpp:10366 + auto Alignment = CGM.getNaturalPointeeTypeAlignment( + E->getArg(0)->IgnoreParenCasts()->getType()); Ops[0] = Builder.CreateBitCast(Ops[0], llvm::PointerType::getUnqual(VTy)); ---------------- LukeGeeson wrote: > simon_tatham wrote: > > What effect is this change of strategy having on the alignment computation, > > for the already-supported instances of this builtin? > > > > It //looks// to me as if `__builtin_neon_vld1_v` with (say) a `uint8_t *` > > pointer argument will now compute `Alignment=1` (the natural alignment of > > the pointee type), whereas it would previously have computed `Alignment=8` > > (the size of the whole vector being loaded or stored). > > > > Is that intentional? Or accidental? Or have I completely misunderstood > > what's going on? > > > > (Whichever of the three, some discussion in the commit message would be a > > good idea, explaining why this change does or does not make a difference, > > as appropriate.) > Clang was incorrectly assuming that all the pointers from which loads were > being generated for vld1 intrinsics were aligned according to according to > the intrinsics result type. This causes alignment faults on the code > generated by the backend. > This fixes the issue so that alignment is based on the type of the pointer > provided to as input to the intrinsic. > > @pratlucas has done some work on this in parallel > https://reviews.llvm.org/D79721 which has been approved and may overrule this > particular line of code. > > I shall add a note to the commit message, and tentatively mark this as fixed, > given it's liable to adopt the work of Lucas. > Hi @LukeGeeson , Just as a heads up, some changes to this implementations were requested on D79721. The usage of `CGM.getNaturalPointeeTypeAlignment` and `IgnoreParenCasts()` was causing problems on certain argument types, so the alignment is now captured from the expression itself when it is emitted. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D80716/new/ https://reviews.llvm.org/D80716 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits