================
@@ -326,25 +326,25 @@ struct LazyOffsetPtr {
///
/// If the low bit is clear, a pointer to the AST node. If the low
/// bit is set, the upper 63 bits are the offset.
- mutable uint64_t Ptr = 0;
+ mutable uintptr_t Ptr = 0;
public:
LazyOffsetPtr() = default;
- explicit LazyOffsetPtr(T *Ptr) : Ptr(reinterpret_cast<uint64_t>(Ptr)) {}
+ explicit LazyOffsetPtr(T *Ptr) : Ptr(reinterpret_cast<uintptr_t>(Ptr)) {}
- explicit LazyOffsetPtr(uint64_t Offset) : Ptr((Offset << 1) | 0x01) {
- assert((Offset << 1 >> 1) == Offset && "Offsets must require < 63 bits");
+ explicit LazyOffsetPtr(uintptr_t Offset) : Ptr((Offset << 1) | 0x01) {
+ assert((Offset << 1 >> 1) == Offset && "Offsets must fit in addressable
bits");
if (Offset == 0)
Ptr = 0;
}
LazyOffsetPtr &operator=(T *Ptr) {
- this->Ptr = reinterpret_cast<uint64_t>(Ptr);
+ this->Ptr = reinterpret_cast<uintptr_t>(Ptr);
return *this;
}
- LazyOffsetPtr &operator=(uint64_t Offset) {
- assert((Offset << 1 >> 1) == Offset && "Offsets must require < 63 bits");
+ LazyOffsetPtr &operator=(uintptr_t Offset) {
----------------
jrtc27 wrote:
> > That doesn't work for getAddressOfPointer
>
> Maybe we can just define away the need for `getAddressOfPointer`.
If you can do that then the current code works just fine :)
> > so we need to preserve at least 64 bits in this structure.
>
> Hmm. We're only really preserving 63 bits here, so that might be a problem.
>
> > That doesn't work for getAddressOfPointer
>
> Maybe we can just define away the need for `getAddressOfPointer`.
>
> > (and doesn't work for CHERI either, but there are many instances of that
> > idiom in Clang to fix...).
>
> Is the CHERI problem just the assumption that `uint64_t` is at least as wide
> as `uintptr_t`, or is there a broader issue with round-tripping through an
> integer type at all? At any rate, if we need this type to be implemented
> substantially differently on CHERI, that's fine, but I'd like to not regress
> performance on other platforms because of it.
The problem is that uint64_t cannot hold a pointer on CHERI, but uintptr_t can
round-trip just fine. The approach I've used downstream in the past when
prototyping self-hosted CHERI LLVM was to use uintptr_t when its range is at
least uint64_t's and to fall back on uint64_t otherwise (effectively using
uint64_t for ILP32 and uintptr_t otherwise). Though if and when I ever get back
to cleaning all that up and upstreaming it I'd like to abstract it into a
reusable helper rather than replicating the slightly messy std::conditional_t
pattern.
https://github.com/llvm/llvm-project/pull/111995
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