[llvm] [InstCombine] Fix buggy transform in foldNestedSelects; PR 71330 (PR #71489)

[via llvm-commits]

================
@@ -0,0 +1,229 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
+; RUN: opt -O3 -S < %s | FileCheck %s
----------------
goldsteinn wrote:

```
./bin/opt -O3 --print-pipeline-passes -
```
Which results in:
```
annotation2metadata,forceattrs,inferattrs,coro-early,function<eager-inv>(lower-expect,simplifycfg<bonus-inst-threshold=1;no-forward-switch-cond;no-switch-range-to-icmp;no-switch-to-lookup;keep-loops;no-hoist-common-insts;no-sink-common-insts;speculate-blocks;simplify-cond-branch>,sroa<modify-cfg>,early-cse<>,callsite-splitting),openmp-opt,ipsccp,called-value-propagation,globalopt,function<eager-inv>(mem2reg,instcombine<max-iterations=1;no-use-loop-info;no-verify-fixpoint>,simplifycfg<bonus-inst-threshold=1;no-forward-switch-cond;switch-range-to-icmp;no-switch-to-lookup;keep-loops;no-hoist-common-insts;no-sink-common-insts;speculate-blocks;simplify-cond-branch>),always-inline,require<globals-aa>,function(invalidate<aa>),require<profile-summary>,cgscc(devirt<4>(inline,function-attrs<skip-non-recursive-function-attrs>,argpromotion,openmp-opt-cgscc,function<eager-inv;no-rerun>(sroa<modify-cfg>,early-cse<memssa>,speculative-execution,jump-threading,correlated-propagation,simplifycfg<bonus-inst-threshold=1;no-forward-switch-cond;switch-range-to-icmp;no-switch-to-lookup;keep-loops;no-hoist-common-insts;no-sink-common-insts;speculate-blocks;simplify-cond-branch>,instcombine<max-iterations=1;no-use-loop-info;no-verify-fixpoint>,aggressive-instcombine,libcalls-shrinkwrap,tailcallelim,simplifycfg<bonus-inst-threshold=1;no-forward-switch-cond;switch-range-to-icmp;no-switch-to-lookup;keep-loops;no-hoist-common-insts;no-sink-common-insts;speculate-blocks;simplify-cond-branch>,reassociate,constraint-elimination,loop-mssa(loop-instsimplify,loop-simplifycfg,licm<no-allowspeculation>,loop-rotate<header-duplication;no-prepare-for-lto>,licm<allowspeculation>,simple-loop-unswitch<nontrivial;trivial>),simplifycfg<bonus-inst-threshold=1;no-forward-switch-cond;switch-range-to-icmp;no-switch-to-lookup;keep-loops;no-hoist-common-insts;no-sink-common-insts;speculate-blocks;simplify-cond-branch>,instcombine<max-iterations=1;no-use-loop-info;no-verify-fixpoint>,loop(loop-idiom,indvars,loop-deletion,loop-unroll-full),sroa<modify-cfg>,vector-combine,mldst-motion<no-split-footer-bb>,gvn<>,sccp,bdce,instcombine<max-iterations=1;no-use-loop-info;no-verify-fixpoint>,jump-threading,correlated-propagation,adce,memcpyopt,dse,move-auto-init,loop-mssa(licm<allowspeculation>),coro-elide,simplifycfg<bonus-inst-threshold=1;no-forward-switch-cond;switch-range-to-icmp;no-switch-to-lookup;keep-loops;hoist-common-insts;sink-common-insts;speculate-blocks;simplify-cond-branch>,instcombine<max-iterations=1;no-use-loop-info;no-verify-fixpoint>),function-attrs,function(require<should-not-run-function-passes>),coro-split)),deadargelim,coro-cleanup,globalopt,globaldce,elim-avail-extern,rpo-function-attrs,recompute-globalsaa,function<eager-inv>(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;>,infer-alignment,loop-load-elim,instcombine<max-iterations=1;no-use-loop-info;no-verify-fixpoint>,simplifycfg<bonus-inst-threshold=1;forward-switch-cond;switch-range-to-icmp;switch-to-lookup;no-keep-loops;hoist-common-insts;sink-common-insts;speculate-blocks;simplify-cond-branch>,slp-vectorizer,vector-combine,instcombine<max-iterations=1;no-use-loop-info;no-verify-fixpoint>,loop-unroll<O3>,transform-warning,sroa<preserve-cfg>,infer-alignment,instcombine<max-iterations=1;no-use-loop-info;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;no-switch-to-lookup;keep-loops;no-hoist-common-insts;no-sink-common-insts;speculate-blocks;simplify-cond-branch>),globaldce,constmerge,cg-profile,rel-lookup-table-converter,function(annotation-remarks),verify
```

https://github.com/llvm/llvm-project/pull/71489