This will later allow us to use the SVE2 constructive variant of EXT
without requiring a MOV. That is because that variant of EXT requires
two consecutive Z registers as input. As a consequence, extracting a
subvector from e.g. z2 into z0 would require:
  z3 = MOV z2
  z0 = EXT_ZZI_B { z2, z3 }, idx

With this change, the z3 part of the { z2, z3 } tuple will be marked as
undef, allowing the MOV to be simplified.

We just need to add patterns for EXT_ZZI_B now, currently only the the
destructive EXT_ZZI variant is selected.

This reworks an existing optimization on the fixed vector (shuffle
based) deinterleave lowering into a DAG combine. This has the effect of
making it kick in much more widely - in particular on the deinterleave
intrinsic (i.e. scalable) path, deinterleaveN (without load) lowering,
but also the intrinsic lowering paths.

If a user passed an invalid value to `-march`, an assertion failure
happened in the AArch64 multilib logic.

But an invalid `-march` value is an expected case that should be handled
via error messages.

This patch removes the requirement that the `-march` value must be
valid.

Add support for generating shader arguments as global variables in the
SPIR-V module when the argument in question is a SPIR-V image.

Add lit tests to execute the new logic and check global variables are
being generated.

---------

Signed-off-by: Jack Frankland <jack.frankland@arm.com>

PR #150392 added the nuw flag to some G_PTR_ADD MIR instructions, this
patch updates the tests for the experimental M68k backend to expect
them.

Should fix buildbot failures like
https://lab.llvm.org/buildbot/#/builders/27/builds/13793

These map to SPIR-V instructions, which are long supported by the llvm
SPIR-V target [1] and the llvm-spirv translator [2].

Intel's offline compiler (ocloc) and OpenCL implementation trivially
supports these, by having these same declarations [3] and relying on
llvm-spirv to map calls to them to their corresponding SPIR-V
instructions.

[1]:
https://github.com/llvm/llvm-project/blob/531cf8298b08eacdf670bac8c28db97a5dc8cb01/llvm/lib/Target/SPIRV/SPIRVBuiltins.td#L1546C11-L1546C27
[2]:
https://github.com/KhronosGroup/SPIRV-LLVM-Translator/blob/10c7569b3c4cb456fbfdcc86c3de45d46c7f5fa8/lib/SPIRV/OCLUtil.h#L327
[3]:
https://github.com/intel/intel-graphics-compiler/blob/342c4fb729ff6a20a41e19adc8329ad18ba05660/IGC/BiFModule/Languages/OpenCL/opencl_cth_released.h#L6899