[llvm] [SLP]Disable reused reductions in revec mode for vector scalars (PR #197291)

[via llvm-commits]

Andarwinux wrote:

```llvm
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

define i1 @mi_posix_memalign(ptr %0, i64 %1, i64 %2) {
  %4 = icmp ne i64 %1, 0
  %5 = icmp ne ptr %0, null
  %6 = icmp eq i64 %2, 0
  %7 = and i1 %5, %6
  %8 = and i1 %4, %7
  %9 = icmp samesign ult i64 %1, 2
  %10 = select i1 %8, i1 %9, i1 false
  ret i1 %10
}
```
```
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: clang -O3 -mllvm -slp-revec -c test.ll
1.	Optimizer
2.	Running pass "function<eager-inv>(drop-unnecessary-assumes,float2int,lower-constant-intrinsics,chr,loop(loop-rotate<header-duplication;no-prepare-for-lto;check-exit-count>,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,mergeicmps,expand-memcmp,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 "test.ll"
3.	Running pass "slp-vectorizer" on function "mi_posix_memalign"
#0 0x000061bae80b15d6 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) Signals.cpp:0:0
clang: error: clang frontend command failed due to signal (use -v to see invocation)
```

https://github.com/llvm/llvm-project/pull/197291