Reverts llvm/llvm-project#146297 because #131837 is reverted in #146850

It must be "REQUIRES:", "REQUIRES :" does not actually check
the requirement.

The target is called "x86" not "x86_64".

Two problems here:
* Missing ":" after REQUIRES, so it was never checked for
  and ran anyway.
* The target name is "x86" not "x86_64".

Add abbreviations for icmp/fcmp, store and br, which are the most common
instructions that don't have abbreviations yet. This requires increasing
the abbreviation size to 5 bits.

This gives about 3-5% bitcode size reductions for the clang build.

Reverting because mis-compiles:
- https://github.com/llvm/llvm-project/pull/131837
- https://github.com/llvm/llvm-project/pull/146320
- https://github.com/llvm/llvm-project/pull/146337

createEVLRecipe tries to optimise recipes that use the header mask by
replacing them with their VP equivalents and setting the EVL, allowing
the mask to be removed.

However we currently also convert widened selects to vp.select even
though they don't necessarily use the header mask.

Unlike vp.merge a vp.select only makes the "unused" lanes past EVL
poison, so it's not needed for correctness.

In the same vein as #127180, this patch removes the transform for
VPWidenSelectRecipes and keeps them as plain select instructions to
allow for more optimisations.

RISCVVLOptimizer will still be able to optimise away any VL toggles and
we end up with better code generation across llvm-test-suite and SPEC
CPU 2017.

Previously we only folded TargetGlobalAddresses into the memarg if they
were on their own, so this patch supports folding TargetGlobalAddresses
that are added to some other offset.

Previously we weren't able to do this because we didn't have nuw on the
add, but we can now that getelementptr has nuw and is plumbed through to
the add in 0564d0665b302d1c7861e03d2995612f46613a0f.

Fixes #61930

Reverts llvm/llvm-project#146582

Due to failures on many of Linaro's Linux flang bots:
https://lab.llvm.org/buildbot/#/builders/17/builds/9292

```
******************** TEST 'Flang :: Semantics/windows.f90' FAILED ********************
Exit Code: 1
Command Output (stdout):
--
--- 
+++ 
@@ -0,0 +1,2 @@
expect at 6: User IDs do not exist on Windows. This function will always return 1
expect at 11: Group IDs do not exist on Windows. This function will always return 1
FAIL
--
Command Output (stderr):
--
RUN: at line 1 has no command after substitutions
"/usr/bin/python3.10" /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/flang/test/Semantics/test_errors.py /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/flang/test/Semantics/windows.f90 /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/bin/flang --target=aarch64-pc-windows-msvc -Werror # RUN: at line 2
+ /usr/bin/python3.10 /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/flang/test/Semantics/test_errors.py /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/flang/test/Semantics/windows.f90 /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/bin/flang --target=aarch64-pc-windows-msvc -Werror
--
```