The language reference says about inbounds geps that "if the
getelementptr has any non-zero indices[...] [t]he base pointer has an in
bounds address of the allocated object that it is based on [and]
[d]uring the successive addition of offsets to the address, the
resulting pointer must remain in bounds of the allocated object at each
step."

If (gep inbounds p, (a + 5)) is translated to (gep [inbounds] (gep p,
a), 5) with p pointing to the beginning of an object and a=-4, as the
example in the comments suggests, that's the case for neither of the
resulting geps. Therefore, we need to clear the inbounds flag for both
geps.

We might want to use ValueTracking to check if a is known to be
non-negative to preserve the inbounds flags.

For the AMDGPU tests with scratch instructions, removing the unsound
inbounds flag means that AMDGPUDAGToDAGISel::isFlatScratchBaseLegal sees
no NUW flag at the pointer add, which prevents generation of scratch
instructions with immediate offsets.

For SWDEV-516125.

Always emit canonical i8 GEPs, don't try to preserve the original
element type. As this is a backend pass, trying to preserve the
type is not useful.

Always generate canonical i8 GEPs. Especially as this is a backend
pass, trying to generate a "nice" GEP representation is not useful.

This is a follow-up to b71edfaa4ec3c998aadb35255ce2f60bba2940b0
since I forgot the lit.local.cfg files in that one.

Reformatting is done with `black`.

If you end up having problems merging this commit because you
have made changes to a python file, the best way to handle that
is to run git checkout --ours <yourfile> and then reformat it
with black.

If you run into any problems, post to discourse about it and
we will try to help.

RFC Thread below:

https://discourse.llvm.org/t/rfc-document-and-standardize-python-code-style

Reviewed By: barannikov88, kwk

Differential Revision: https://reviews.llvm.org/D150762

Required some manual updates in AMDGPU/pr23975.ll and
slsr-gep.ll. pr23975.ll had another offset 0 GEP that probably should
not have been deleted.

This reverts commit bda6e5bee04c75b1f1332b4fd1ac4e8ef6c3c247.

See https://lab.llvm.org/buildbot/#/builders/109/builds/15424 for instance

Since d6de1e1a71406c75a4ea4d5a2fe84289f07ea3a1, no attributes is quivalent to
setting attribute to false.

This is a preliminary commit for https://reviews.llvm.org/D99080

Add RUN lines for NPM of -slsr tests that require -separate-const-offset-from-gep

Reviewed By: aeubanks

Differential Revision: https://reviews.llvm.org/D91588