[cfe-dev] Crash on conditional operation with address_space pointer

[Leonard Chan via cfe-dev]

Compiling the following causes clang to crash

char *cmp(__attribute__((address_space(1))) char *x,
__attribute__((address_space(2))) char *y) {
  return x < y ? x : y;
}

with the message: "wrong cast for pointers in different address
spaces(must be an address space cast)!"

The problem seems to be that BitCast is used when
AddressSpaceConversion should be used instead when casting the `y` to
a void *. The error is thrown during code gen where a BitCast expects
the source and dest address space to be the same.

I submitted a patch (https://reviews.llvm.org/D50278) for a fix where
we check for differing address spaces in the operands and perform an
AddressSpaceConversion cast if anyone wants to review it. It seems
that AddressSpaceConversions though were only available when using
OpenCL. I'm not familiar with OpenCL and not sure if this was
intended, but it fixes the crash while still retaining the warning of
using mismatched pointers and all the clang tests pass.

- Leo