[InstCombine] Lost scalarization of vector fdiv with dead lanes

the Following IR:

```llvm
define <2 x float> @test_fdiv(float %a, float %b, i1 %cmp) {
%splatinsert = insertelement <2 x float> poison, float %a, i32 0
%denom = insertelement <2 x float> , float 1.000000e+00, i32 1
%t1 = fdiv <2 x float> %splatinsert, %denom
%freeze.ins = freeze <2 x float> %t1
%splat.op = shufflevector <2 x float> %freeze.ins, <2 x float> undef, <2 x i32>
%t2 = select i1 %cmp, <2 x float> , <2 x float> %splat.op
ret <2 x float> %t2
}
```

was optimized as following by `opt 22.1.0` https://godbolt.org/z/v8cW6xv8z

```llvm
define <2 x float> @test_fdiv(float %a, float %b, i1 %cmp) local_unnamed_addr #0 {
%splatinsert = insertelement <2 x float> poison, float %a, i64 0
%splatinsert.fr = freeze <2 x float> %splatinsert
%t1 = fdiv <2 x float> %splatinsert.fr,
%splat.op = shufflevector <2 x float> %t1, <2 x float> poison, <2 x i32>
%t2 = select i1 %cmp, <2 x float> , <2 x float> %splat.op
ret <2 x float> %t2
}

attributes #0 = { mustprogress nofree norecurse nosync nounwind willreturn memory(none) }
```

but in the opt `20.0.0` used in online Alive-tv (https://alive2.llvm.org/ce/), we can observe the following optimization https://alive2.llvm.org/ce/z/M3gkK7 :

```llvm
define <2 x float> @test_fdiv(float %a, float %b, i1 %cmp) local_unnamed_addr #0 {
%a.fr = freeze float %a
%splat.op.scalar = fdiv float %a.fr, 3.000000e+00
%splat.op = insertelement <2 x float> poison, float %splat.op.scalar, i64 1
%t2 = select i1 %cmp, <2 x float> , <2 x float> %splat.op
ret <2 x float> %t2
}

attributes #0 = { mustprogress nofree norecurse nosync nounwind willreturn memory(none) }
```

How can we get the exact commit hash that was used to build opt?