InstCombine/AMDGPU: Add dimension-aware image intrinsics to SimplifyDemanded

Summary:
Use the expanded features of the TableGen generic tables to avoid manually
adding the combinatorially exploded set of intrinsics. The
getAMDGPUImageDimIntrinsic lookup function is early-out,
i.e. non-AMDGPU intrinsics will never look at the underlying table.

Use a generic approach for getting the new intrinsic overload to keep the
code simple, and make the image dmask handling more generic:
- handle non-sampler image loads
- handle the case where the set of demanded elements is not a prefix

There is some overlap between this code and an optimization that happens
in the backend during code generation. They currently complement each other:

- only the codegen optimization can generate vec3 loads
- only the InstCombine optimization can handle D16

The InstCombine optimization also likely covers more cases since the
codegen optimization is fairly ad-hoc. Ideally, we'll remove the optimization
in codegen once the infrastructure for vec3 is in place (which will probably
take a long time).

Modify the test cases to use dimension-aware intrinsics. This makes it
easier to see that the test coverage for the new intrinsics is equivalent,
and the old style intrinsics will be removed in a follow-up commit anyway.

Change-Id: I4b91ea661413d13004956fe4ef7d13d41b8ce3ad

Reviewers: arsenm, rampitec, majnemer

Subscribers: kzhuravl, wdng, mgorny, yaxunl, dstuttard, tpr, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D48165

llvm-svn: 335230

0 files changed, 0 insertions, 0 deletions