[PATCH] D142388: [clang] Add builtin_nondeterministic_value

Wed Feb 1 07:21:18 PST 2023

aaron.ballman added inline comments.

================
Comment at: clang/lib/CodeGen/CGBuiltin.cpp:3070
+
+    if(Ty->isStructTy()){
+      Address StructAddr = ReturnValue.getValue();
----------------
erichkeane wrote:
> ManuelJBrito wrote:
> > erichkeane wrote:
> > > This gets REALLY complicated, you can't just create a store, this might end up hitting conversion operators/etc, and is subject to triviality/etc, and also probably needs to go through a constructor.  I suspect you're going to prefer to just decide this isn't a valid builtin for structs instead of getting bogged down in that mess.
> > The motivation for this builtin was to match intel's definition of undefined in the lowering of intrinsics such as  https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_mm256_castsi128_si256&expand=628&ig_expand=755,  so struct support isn't critical.
> > So if everyone else agrees i'll drop struct support, do as you suggest and if there are use cases for nondeterministic values of other types add support for them later?
> I suspect I speak for all with my suggestion.  I don't think Aaron/Shafik are concerned with struct support here.
If we reject the code, we can relax that restriction in the future without breaking code, so I think it's fine to not support structures. We can add support for them later if we have a need to do so.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D142388/new/

https://reviews.llvm.org/D142388