arichardson added a comment. In D71499#1801421 <https://reviews.llvm.org/D71499#1801421>, @lebedev.ri wrote:
> (temporarily undoing my review since it looks like things may change) > > In D71499#1801302 <https://reviews.llvm.org/D71499#1801302>, @arichardson > wrote: > > > ... > > > Aha! :) > > In D71499#1801302 <https://reviews.llvm.org/D71499#1801302>, @arichardson > wrote: > > > However, I think this means that for the downstream CHERI codegen > > there is one more case where we need to be careful > > (but that shouldn't matter for upstream). > > For us `uintptr_t` is represented as `i8 addrspace(200)*`. > > As `uintptr_t` can hold values that are plain integers and not pointers, > > we would need to add the inbounds only if the AST type is a pointer, > > and use a non-inbounds GEP for `(u)intptr_t`. > > > I may be missing some details, but won't we get that for free, > since we only do `gep` for pointers already? I believe we would need something like this downstream instead of always creating an inbounds GEP: if (E->getType()->isPointerType()) { // The result must point to the same underlying allocation. This means we // can use an inbounds GEP to enable better optimization. Result = Builder.CreateInBoundsGEP(EmitCastToVoidPtr(Args.Src), Difference, "aligned_result"); } else { // However, for when performing operations on __intcap_t (which is also // a pointer type in LLVM IR), we cannot set the inbounds flag as the // result could be either an arbitrary integer value or a valid pointer. // Setting the inbounds flag for the arbitrary integer case is not safe. assert(E->getType()->isIntCapType()); Result = Builder.CreateGEP(EmitCastToVoidPtr(Args.Src), Difference, "aligned_result"); } > In D71499#1801302 <https://reviews.llvm.org/D71499#1801302>, @arichardson > wrote: > >> Does that sound correct or did I misunderstand something? > > > To //me// this all sounds great. > Since we get to dictate^W define semantics, i'd think we can require > > In D71499#1801302 <https://reviews.llvm.org/D71499#1801302>, @arichardson > wrote: > >> both input and output should be a `Logical pointer`. >> If you want random values, you should be aligning uintptr_t instead. Thank you very much for the useful suggestion! Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D71499/new/ https://reviews.llvm.org/D71499 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
