[GitHub] [incubator-tvm] Light-of-Hers edited a comment on issue #6884: BUG in CodeGenC::PrintSSAAssign

[GitBox <gi...@apache.org>]

Light-of-Hers edited a comment on issue #6884:
URL: https://github.com/apache/incubator-tvm/issues/6884#issuecomment-723707565


   @tqchen Here is an example. The `int8` vectorized scatter operation may cause such problem.
   ```python
   import tvm
   from tvm import te
   
   N = 128
   A = te.placeholder((N, N * 8), name="A", dtype="int8")
   B = te.compute((N, N), lambda i, j: A[i, j * 8], name="B")
   s = te.create_schedule(B.op)
   
   i, j = s[B].op.axis
   s[B].bind(i, te.thread_axis("blockIdx.x"))
   jo, ji = s[B].split(j, nparts=2)
   s[B].reorder(i, ji, jo)
   s[B].vectorize(jo)
   
   mod = tvm.lower(s, [A, B])
   func = tvm.build(mod, target="opencl")
   print(func.imported_modules[0].get_source())
   ```
   The generated opencl code is:
   ```opencl
   __kernel void main_kernel0(__global char* restrict B, __global char* restrict A) {
     for (int j_inner = 0; j_inner < 64; ++j_inner) {
         int2 _1 = (int2)((((((int)get_group_id(0)) * 128) + j_inner))+(64*0), (((((int)get_group_id(0)) * 128) + j_inner))+(64*1));
         int2 _2 = (int2)((((((int)get_group_id(0)) * 1024) + (j_inner * 8)))+(512*0), (((((int)get_group_id(0)) * 1024) + (j_inner * 8)))+(512*1));
         char2 _3 = (0x000000ff << 0) & (A[_2.s0] << 0))|((0x000000ff << 8) & (A[_2.s1] << 8);
         B[_1.s0] = _3.s0;
         B[_1.s1] = _3.s1;
     }
   }
   ```
   Obviously `char2 _3 = (0x000000ff << 0) & (A[_2.s0] << 0))|((0x000000ff << 8) & (A[_2.s1] << 8)` has unmatched brackets.
   The solution is simple. Just removing the if-branches in `CodeGenC::PrintSSAAssign` is okay, like: 
   ```C++
   void CodeGenC::PrintSSAAssign(const std::string& target, const std::string& src, DataType t) {
     PrintType(t, stream);
     stream << ' ' << target << " = ";
     // if (src.length() > 3 && src[0] == '(' && src[src.length() - 1] == ')') {
     //   stream << src.substr(1, src.length() - 2);
     // } else {
     //   stream << src;
     // }
     stream << src;
     stream << ";\n";
   }
   ```


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