<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/92135>92135</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Clang Generating Invalid SPIRV
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          Calandracas606
      </td>
    </tr>
</table>

<pre>
    I am trying to compile C++ for OpenCL kernels to spirv, however clang is creating invalid spirv (verified with `spirv-val`)

clang 18.1.4 built from source on x86_64 linux

I am using the `-O` flag, which appears to be experimental:
https://github.com/KhronosGroup/OpenCL-Guide/blob/main/chapters/os_tooling.md

simple reproducer `kernel.clcpp`:
```cpp
void sample(read_only image2d_t in_img, write_only image2d_t out_img) {

  const int col = get_global_id(0);
  const int row = get_global_id(1);

  const sampler_t samplerA = CLK_NORMALIZED_COORDS_FALSE |
 CLK_ADDRESS_CLAMP_TO_EDGE | CLK_FILTER_NEAREST;

  float4 px = {0.0F, 0.0F, 0.0F, 1.0F};
  for (int i = 0; i < 3; ++i) {
    for (int j = 0; j < 3; ++j) {
      float4 val = read_imagef(in_img, samplerA, int2{col + i, row + i});
      px += val.xxxx;
    }
  }

 write_imagef(out_img, int2{col, row}, px);
};
```
I try to compile with:

```
clang -c -target spirv64 -O -o sample.spv kernel.clcpp
spirv-val sample.spv
```

i get the output:
```
error: line 51: Block '17[%17]' is already a merge block for another header
  %_Z6sample14ocl_image2d_ro14ocl_image2d_wo = OpFunction %void None %9
```
when I remove the `-O` flag, `spirv-val` no longer reports an error

when i manually invoke `llvm-spirv` and `spirv-opt` there is no error:
```
clang -c -target spirv64 -emit-llvm -o sample2.bc kernel.clcpp
llvm-spirv sample2.bc -o sample2.spv
spirv-opt sample2.spv -o sample2_opt.spv
spirv-val sample2_opt.spv
```

please let me know if this is not the correct area to report this bug, so I can report it elsewhere
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJyUVktv4zgM_jXKhUhgK47dHHLIswimMxm0gz3MxZBlxlYrS4YsJ-m_X0jOw2mDBbYoohdJkR_Jz2JNIwqFOCOTBZmsBqy1pTazJZNM5YZx1sRBPMh0_jnbAqvAmk-hCrAauK5qIRGWhC4IXcBeG9jVqJYv8IFGoWycVFMLcyB0CaU-4gENcMlUAaIBbpBZZ0uoA5Mi70SB0KcDGrEXmMNR2BJIHPiT4YFJEgeETkmwIsG8--3MhU-jcBRB1gppYW90BY1uDUfQCk5PcRpHIIVqT31NH07b-GhKdNcMdyQOYC9Z4Rw-loKXwOoamfGhZAh4qtGICpVlkozPhkpr68at6IbQTSFs2WYjritCNz9Ko5Vuno1ua0I3HTzD51bkSOgmkzojdFMxoQjd8JLVFk1D6EY3qdVaClWMqrzvcyOqWiIYrI3OW47Gud2hPeKS17UD6OKXm_t_t-93DtrBzJwNQp8MsjzVSn6CqFiBNE8tCJWKqgvfCItfj3Vru_MpkGTR9wyAa9U4Axa4lkDGKyjQpoXUGZOpyAl98rkbL74rGH18qBD2Fe7VuihMep3NvYXly4_01-715_xl-3e9Spe73evqLd3MX97WQJLl2YaTmq9Wr-u3t3T5Mv_5O_2zS9erZy_jTzfblz_r1_TXev66fvvzzYe91MxGUJ_8pSRZBKNg41D7OoZuTFa9qF2bEPrkwhZeOyDjhZ8uYeymXTuJO4wB7hTfb4rvXxXfvyle3T2wLi8-8T6pe2_wkvILkm4ulKUkWfhU0gUIt-fT5BfJ6j6V7s-BQRfO_oHJ0el0Ot0JOJ3z4jo9b3SldnXoWmR9L873-5uXUJ_uKqMH8LXoL01uzWefrRyl3DrkkUrHKEMOQ8tMgbbjpTiC4Q6G-gzSqKkPcNd4XX9eiKon9vCS7le4ivfso1tbt_Z763ZLNEYbMp47EkOYhG66kJp_AKFJmDjqphM3rghNHLcy6XL8CQwqNAVC5oVdBTGlbYkGSmQ5mmtG6CT9G3c-h5HmMr30vNH366P2JbSrN63iVmjldD2v_NIK3WL6MIRjiQq2YLDSB3xMuF-IHpQGqVWBxvGdNrYBpqCDooehNyygYqpl0pGVOugPb13KQzXsvj9xAEzltxt0bd2eQwIdXkrDBeP_WRNYCTt0N91qg44y_qA2bu705Xpa11q5-tg_6kmmurZfpW819-X4YeHVElmDINFChfCh9BHEHmwpmg6Nrii5Nga5BWaQuR7q0tCJZW1HGRq2wJm6nAkLKBs8OmAH-WycT8dTNsBZmISTJAijcTIoZxnHCQ9jOuWcRtNkOkn2LMr4NIgTypMJH4gZDWgUTMIonETjSTya0jCPs4jzMGZhMh6TKMCKCTlyoI60KQaiaVqcTWk4ngwky1A2_kVDqU8dodQ9bszMJyFri4ZEgRSNbW4WrLASZ0uf6WdUaLrXyfb8Onn7vX39Z9AaOfuP770zdh6GtdHvyC2hG--b-6579_4NAAD__67l3C4">