[Analysis] Cache generation of SCEV expander overflow checks (#213013)
When creating SCEV checks as part of loop vectorisation we often
generate overflow checks, which leads to lots of duplicated calls to the
umul_with_overflow intrinsic. These calls should be cleaned up during
codegen. However, it is unfortunate that the current LLVM method of
calculating the cost of IR in a block involves looping over each
instruction and adding the costs individually with no thought to the
trivial CSE or DCE optimisations that would take place. In the absence
of a more sophisticated method of cost analysis, for now I've chosen to
explicitly CSE these overflow checks during SCEV expansion.
llvm-project
1768978e - [Analysis] Cache generation of SCEV expander overflow checks (#213013)
