HIPIFY | HIPIFY: Convert CUDA to Portable C++ Code | GPU library

1. Yes, there are new instructions in GPU GCN3 such as ds_bpermute and ds_permute which can provide the functionality such as __shfl() and even more

2. These ds_bpermute and ds_permute instructions use only route of Local memory (LDS 8.6 TB/s), but don't actually use Local memory, this allows to accelerate data exchange between threads: 8.6 TB/s < speed < 51.6 TB/s: http://gpuopen.com/amd-gcn-assembly-cross-lane-operations/

They use LDS hardware to route data between the 64 lanes of a wavefront, but they don’t actually write to an LDS location.

1. Also there are Data-Parallel Primitives (DPP) - is especially powerful when you can use it since an op can read registers of neighboring workitems directly. I.e. DPP can access to neighboring thread (workitem) at full speed ~51.6 TB/s

http://gpuopen.com/amd-gcn-assembly-cross-lane-operations/

now, most of the vector instructions can do cross-lane reading at full throughput.

For example, wave_shr-instruction (Wavefront shift right) for Scan algorithm:

More about GCN3: https://github.com/olvaffe/gpu-docs/raw/master/amd-open-gpu-docs/AMD_GCN3_Instruction_Set_Architecture.pdf

New Instructions

• “SDWA” – Sub Dword Addressing allows access to bytes and words of VGPRs in VALU instructions.
• “DPP” – Data Parallel Processing allows VALU instructions to access data from neighboring lanes.
• DS_PERMUTE_RTN_B32, DS_BPERMPUTE_RTN_B32.

...

DS_PERMUTE_B32 Forward permute. Does not write any LDS memory.