nikic added inline comments.
================ Comment at: clang/lib/CodeGen/Address.h:30 + // Int portion stores lower 3 bits of the log of the alignment. + llvm::PointerIntPair<llvm::Type *, 3, unsigned> ElementType; ---------------- dblaikie wrote: > aeubanks wrote: > > nikic wrote: > > > Are we guaranteed 3 bits even on 32-bit architectures? > > Apparently not, a static assert fires for a 32-bit build of clang. I was > > assuming 3 was fine based on the PointerIntPair comments. > > ``` > > /// PointerIntPair - This class implements a pair of a pointer and small > > /// integer. It is designed to represent this in the space required by one > > /// pointer by bitmangling the integer into the low part of the pointer. > > This > > /// can only be done for small integers: typically up to 3 bits, but it > > depends > > /// on the number of bits available according to PointerLikeTypeTraits for > > the > > /// type. > > ``` > > > > I suppose we could have a separate 32-bit vs 64-bit implementation of > > `Address`, although that's not very nice. > You can get more spare bits by overaligning the type that you're pointing to, > if that's suitable/workable. We do that in a few places in LLVM for this sort > of reason. As we're storing pointers to core LLVM types here (Value and Type), I don't think it's possible to over-align them. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D117262/new/ https://reviews.llvm.org/D117262 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
