[PATCH] D32423: Constant fold barriers of null and undef

[Davide Italiano via Phabricator via llvm-commits]

davide added inline comments.


================
Comment at: lib/Analysis/ConstantFolding.cpp:1779-1783
+    if (isa<ConstantPointerNull>(Operands[0])) {
+      if (IntrinsicID == Intrinsic::invariant_group_barrier)
         return Operands[0];
       return nullptr;
     }
----------------
Prazek wrote:
> majnemer wrote:
> > Isn't this only valid if the address space is zero?
> True, but can you pass pointer from another addrspace to invariant.group.barrier?
> 
> When I try
>   %X = addrspacecast i8* null to i8 addrspace(1)*
>   %b2 = call i8* @llvm.invariant.group.barrier(i8* %X)
> 
> I get
>    error: '%X' defined with type 'i8 addrspace(1)*'
> 
> I could add this line:
>   cast<PointerType>(Operands[0]->getType())->getAddressSpace() == 0
> but I won't be able to test it in any way if I am not wrong.
> 
Not positive about this, but does it work if you do:

```
  %b2 = call i8* @llvm.invariant.group.barrier(i8* addrspace(4)* @global0)   
```

where

```
@global0 = addrspace(4) constant i8* null 
```


https://reviews.llvm.org/D32423