Created attachment 133257 [details]
Test case

Hi,

The following kernel computes b[0] = 127.0 when c[0] = 0.0, d = 256, and global size is 1x1x1:

kernel void A(global float* b, global float* c, const int d) {
  int e = get_global_id(0);
  b[e] = (char)(c[e] + d);
}

Expected result: 0.0. Actual result: 127.0. Expected result confirmed on a number of different OpenCL implementations, including Intel's proprietary driver for the same CPU.

Interestingly, changing the line to 'b[e] = (char)(d);' yields the correct result, despite c[e] = 0.0.

Hardware: Intel(R) HD Graphics Haswell GT2 Desktop
Driver: OpenCL 1.2 beignet 1.3, using llvm 3.6
OS: Ubuntu Linux 16.04

Full test case attached.

Cheers,
Chris