[llvm] [SROA] Only try additional vector type candidates when needed (PR #77678)

[Craig Topper via llvm-commits]

topperc wrote:

> Thanks @topperc -- do you have a test case I can look at?

here's a test https://godbolt.org/z/sWEcxfYje

https://github.com/llvm/llvm-project/pull/77678