<html>
    <head>
      <base href="https://llvm.org/bugs/" />
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - Macro protected __device__ function and identical host function collide in global"
   href="https://llvm.org/bugs/show_bug.cgi?id=27270">27270</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Macro protected __device__ function and identical host function collide in global
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>CUDA
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedclangbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>crtrott@sandia.gov
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=16183" name="attach_16183" title="Reproducer">attachment 16183</a> <a href="attachment.cgi?id=16183&action=edit" title="Reproducer">[details]</a></span>
Reproducer

If I have a __device__ function and a __host__ function with only one of them
visible at the time through protection of __CUDACC__ && __CUDA_ARCH__ the
compile will stop on global functions because it thinks I want to call the
__host__ function. My current suspicion is that during the host compilation
pass it still sees the global function, and it sees the __host__ function and
thinks I call the latter from the former. Here is the simplified pattern:

#ifdef __CUDA_ARCH__
__device__ inline void foo() {}
#else
inline void foo() {}
#endif

__global__ bar() {
  foo();
}

In the attached reproducer this produces the following error with clang (while
it works with nvcc):

/////////////
main.cpp:21:43: error: no matching function for call to 'c_func'
   a[blockIdx.x*blockDim.x+threadIdx.x] = c_func();
                                          ^~~~~~
main.cpp:11:12: note: candidate function not viable: call to __host__ function
from __global__ function
inline int c_func() {return 1;}
           ^
1 error generated.
////////////

The attached reproducer has two workaround solutions in it. To use them build
with
./build_clang -DWORKAROUND=1 
./build_clang -DWORKAROUND=2
otherwise just use
./build_clang 
to get the error. You will need to change the paths in the build script though.</pre>
        </div>
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