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

[Jeffrey Byrnes via llvm-commits]

jrbyrnes wrote:

Hi @topperc , sure -- 

We should be able to resolve the regression if we initially consider some but not all of the LodStoreTys (don't consider ptr or vector ptr types). I can put up a PR soon for this.

At a higher level, though, this PR was a workaround for another commit which caused regressions. So the above will be a workaround for a workaround which feels messy. Not suggesting we revert the initial commit due to the benefits it provides, but perhaps we should reconsider the ptr type handling for promotions -- which seems to be the root of this workaround chain.

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