d3edc94d11
This PR re-lands #165873. This PR extends the gpu.subgroup_mma_* ops to support fp64 type. The extension requires special handling during the lowering to nvvm due to the return type for load ops for fragment a and b (they return a scalar instead of a struct). The original PR did not guard the new test based on the required architecture (sm80) which lead to a failure on the cuda runners with T4 GPUs.