jdoerfert added a comment. In D74935#1908607 <https://reviews.llvm.org/D74935#1908607>, @jeroen.dobbelaere wrote:
> [...] > So, adding the 'noalias' attribute to %pA and %pB will change the behavior > of foo(). > > hmm... this explanation is maybe getting too long ? > The short conclusion should be: > > - adding 'noalias' to a pointer argument, because it is only used to read > memory, might lead to 'wrong code' > - two 'noalias' pointer arguments should not overlap or relaxed: > - two 'noalias' pointer arguments can only overlap if they (at any level of > indirection) are never used to write to memory. I think we conflate two things here: 1. The modifications to the LangRef which should be in accordance with the C standard (at least I haven't seen you contradict the new wording directly). 2. The extended `noalias` deduction D73428 <https://reviews.llvm.org/D73428>. If you look at the commit message in D73428 <https://reviews.llvm.org/D73428>, it says that `noalias` is not just derived for all `readonly` arguments. In your example we access `unknown` memory, e.g., `**pA=42`, so case (1) cannot be applied. For case (2) we need to show that the loads of `pA` and `pB` do not alias, which we cannot. WDYT? Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D74935/new/ https://reviews.llvm.org/D74935 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
