[PATCH] D93927: [ArgPromotion] Copy !range metadata for loads.

[Nikita Popov via Phabricator via llvm-commits]

nikic reopened this revision.
nikic added a comment.
This revision is now accepted and ready to land.

Here is a further reduction:

  define i32* @caller(i1 %c, i32** dereferenceable(8) %arg) {
    %p = call i32* @func(i1 %c, i32** dereferenceable(8) %arg)
    ret i32* %p
  } 
  
  define internal i32* @func(i1 %c, i32** dereferenceable(8) %arg) {
  bb:
    br i1 %c, label %if, label %else
    
  if:
    %p = load i32*, i32** %arg, align 8, !nonnull !{}
    ret i32* %p 
  
  else:
    ret i32* null                                    
  } 

It's okay to promote the load, because the pointer is dereferenceable, but it's not okay to transfer the metadata. There are two pre-existing bugs in this respect: We were already transfering the AA metadata, which is also incorrect. And we were transferring the load alignment (this probably shouldn't be transferred at all but rather a precondition). We can only transfer metadata if the load is guaranteed-to-execute from the entry of the function.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D93927/new/

https://reviews.llvm.org/D93927