[llvm] [ArgPromotion] Infer parameter attributes on functions (PR #110245)

[Matthew Devereau via llvm-commits]

================
@@ -743,6 +743,10 @@ static bool findArgParts(Argument *Arg, const DataLayout &DL, AAResults &AAR,
   // Okay, now we know that the argument is only used by load instructions, and
   // it is safe to unconditionally perform all of them.
 
+  // We can infer `nocapture readonly` as the argument is only used by loads.
+  Arg->getParent()->addParamAttr(Arg->getArgNo(), Attribute::NoCapture);
+  Arg->getParent()->addParamAttr(Arg->getArgNo(), Attribute::ReadOnly);
----------------
MDevereau wrote:

Not that it looks particularly better, but I think you can one-line this with
```c++
  Arg->getParent()->addParamAttrs(Arg->getArgNo(),
                                  AttrBuilder(Arg->getContext())
                                      .addAttribute(Attribute::NoCapture)
                                      .addAttribute(Attribute::ReadOnly));
``` 

https://github.com/llvm/llvm-project/pull/110245