[SimplifyCFG] Don't block sinking for allocas if no phi created (#104579)

SimplifyCFG sinking currently does not sink loads/stores of allocas,
because historically SROA was unable to handle the resulting IR. Since
then, SROA both learned to speculate loads/stores over selects and phis,
*and* SimplifyCFG sinking has been deferred to the end of the function
simplification pipeline, which means that SROA happens before it.

As such, I believe that this workaround should no longer be necessary.
Given how sensitive SimplifyCFG sinking seems to be, this patch takes a
very conservative step towards removing this, by allowing sinking if we
don't actually need to form a phi over the pointer argument.

This fixes https://github.com/llvm/llvm-project/issues/104567, where
sinking a store to an escaped alloca allows converting a switch into
arithmetic.

0 files changed, 0 insertions, 0 deletions