Clspv crashes copying structs (using llvm.memcpy) with pointer arithmetic and address space inference about clspv HOT 2 CLOSED

This one is quite complicated

TL;DR: https://godbolt.org/z/zj9zedzf8

• Memory is in the global address space, thus the cast to (struct S*) should be (global Struct *)
• Because Memory is just used to be casted to long, we need to compile with -cl-kernel-arg-info to help clspv figure out Memory type. Note that clvk compiles by default with this option.
• As you are doing pointer arithmetic, you definitively need to use physical addressing (compile with -physical-storage-buffers -arch=spir64). We have a LogicalPointerToIntPass but it does not support this case. It should be able to be implemented, but that would require some work.

With all that, this example is compiled correctly.

from clspv.

Thank you for looking into this Mr. Jodin.

The interesting thing is, in CLC++ mode, Clspv infers address spaces when memcpy is not involved, as you can see below. Clspv just converts remaining generic address spaces to global in the LowerAddrSpaceCastPass for simple loads and stores. However, there seems to be some difficulty doing this for memcpy.

When looking at Clang's IR from CLC++ you will see it extensively emits the generic addrspace(4), even when No function calls or generics are used! Because the programmer has no control of these, Clspv handling the generic spaces with memcpy is probably essential for stability. Here are some additional observations at #1179

Here the (int*) inference is working. Also when using external Clang compilation with optimizations, S* inference works too, because it has been reduced to a single int i1.

struct S { int i1; };

kernel void Kernel(global void* Memory)
{
    long a = (long) Memory;

    * (int*) a = 0; // OK, address space inferred
    // * (S*) a = {}; // Fails, address space not inferred. OK if externally optimized
    // * (global S*) a = {}; // OK, address space explicit
}

https://godbolt.org/z/qj4WhbMG1

Isn't it nice to have the modern syntax! :-)

from clspv.