[llvm] [VPlan] Handle WidenGEP in narrowToSingleScalars (PR #166740)

[David Spickett via llvm-commits]

DavidSpickett wrote:

An assertion is failing when trying to compile 

This is the one with the smallest commit list: https://lab.llvm.org/buildbot/#/builders/4/builds/10404
It is failing on single stage too though: https://lab.llvm.org/buildbot/#/builders/17/builds/12564

So far it has failed on SVE and SVE2, vector length specific and agnostic. SIMD only AArch64 and Arm 32-bit builds are still in progress.

Our build logs have jumbled output due to parallel jobs, but here's the first bit of the failure:
```
clang: /home/tcwg-buildbot/worker/clang-aarch64-sve-vls-2stage/llvm/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp:2529: virtual void llvm::VPWidenGEPRecipe::execute(VPTransformState &): Assertion `any_of(operands(), [](VPValue *Op) { return !Op->isDefinedOutsideLoopRegions(); }) && "Expected at least one loop-variant operand"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.  Program arguments: /home/tcwg-buildbot/worker/clang-aarch64-sve-vls-2stage/stage2.install/bin/clang -DNDEBUG -mcpu=neoverse-512tvb -msve-vector-bits=256 -O3 -fno-strict-aliasing -ffp-contract=off -DFMA_DISABLED=1 -ffp-contract=off -DFMA_DISABLED=1 -MD -MT MultiSource/Applications/oggenc/CMakeFiles/oggenc.dir/oggenc.c.o -MF CMakeFiles/oggenc.dir/oggenc.c.o.d -o CMakeFiles/oggenc.dir/oggenc.c.o -c /home/tcwg-buildbot/worker/clang-aarch64-sve-vls-2stage/test/test-suite/MultiSource/Applications/oggenc/oggenc.c
1.  <eof> parser at end of file
2.  Optimizer
3.  Running pass "function<eager-inv>(drop-unnecessary-assumes,float2int,lower-constant-intrinsics,chr,loop(loop-rotate<header-duplication;no-prepare-for-lto>,loop-deletion),loop-distribute,inject-tli-mappings,loop-vectorize<no-interleave-forced-only;no-vectorize-forced-only;>,drop-unnecessary-assumes,infer-alignment,loop-load-elim,instcombine<max-iterations=1;no-verify-fixpoint>,simplifycfg<bonus-inst-threshold=1;forward-switch-cond;switch-range-to-icmp;switch-to-arithmetic;switch-to-lookup;no-keep-loops;hoist-common-insts;no-hoist-loads-stores-with-cond-faulting;sink-common-insts;speculate-blocks;simplify-cond-branch;no-speculate-unpredictables>,slp-vectorizer,vector-combine,instcombine<max-iterations=1;no-verify-fixpoint>,loop-unroll<O3>,transform-warning,sroa<preserve-cfg>,infer-alignment,instcombine<max-iterations=1;no-verify-fixpoint>,loop-mssa(licm<allowspeculation>),alignment-from-assumptions,loop-sink,instsimplify,div-rem-pairs,tailcallelim,simplifycfg<bonus-inst-threshold=1;no-forward-switch-cond;switch-range-to-icmp;switch-to-arithmetic;no-switch-to-lookup;keep-loops;no-hoist-common-insts;hoist-loads-stores-with-cond-faulting;no-sink-common-insts;speculate-blocks;simplify-cond-branch;speculate-unpredictables>)" on module "/home/tcwg-buildbot/worker/clang-aarch64-sve-vls-2stage/test/test-suite/MultiSource/Applications/oggenc/oggenc.c"
4.  Running pass "loop-vectorize<no-interleave-forced-only;no-vectorize-forced-only;>" on function "floor1_look"
```
I'll get you a reproducer from one of the bots.

https://github.com/llvm/llvm-project/pull/166740