[code-reflection] RFR: Proposal for Vector Types for GPUs (OpenCL and CUDA backends)

[Juan Fumero]

This PR opens a new proposal to integrate an API for representing explicit vector types in HAT. 

The way to operate is as follows:


Float4 vA = a.float4View(index * 4);
Float4 vB = b.float4View(index * 4);
Float4 vC = Float4.add(vA, vB);
c.storeFloat4View(vC, index * 4);


Java programmers can load/store float4 chunks within one instruction by using array views. These views operate on GPU's global memory, but we can add similar concepts for local/shared and private memory.  

Additionally, Java/HAT developers can access lanes within the vector instance by name:


vA.x(myNewValue);
float foo = vA.z();
``` 

We will iterate over this proposal. 

How to test?

For CUDA

HAT=SHOW_CODE,INFO,SHOW_COMPILATION_PHASES java @hat/otest ffi-cuda oracle.code.hat.TestVectorTypes


For OpenCL:



HAT=SHOW_CODE,INFO,SHOW_COMPILATION_PHASES java @hat/otest ffi-opencl oracle.code.hat.TestVectorTypes


This PR also introduces a new option to debug the HAT Dialect Phases. 


HAT=SHOW_COMPILATION_PHASES ...

-------------

Commit messages:
 - [hat] clean-up old code
 - [hat] float4 support for the CUDA backend types generalized
 - [hat] Padding for copyFrom/copyTo functions
 - Merge branch 'code-reflection' into hat/vector/types
 - [hat] Example of matmul with 2D RT + vector loads
 - [hat] Matmul with 2D register tiling + vector loads/stores working
 - [hat] clean-up test
 - [hat] CUDA backend with the right accessor for loading/storing float4 views
 - [hat] Allow float4 to/from local/private memory
 - [hat] Offsets for S32Arrays fixed
 - ... and 14 more: https://git.openjdk.org/babylon/compare/e5dfd23b...5f37c6f7

Changes: https://git.openjdk.org/babylon/pull/606/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=606&range=00
  Stats: 3350 lines in 44 files changed: 3219 ins; 86 del; 45 mod
  Patch: https://git.openjdk.org/babylon/pull/606.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/606/head:pull/606

PR: https://git.openjdk.org/babylon/pull/606