DAGCombiner doesn't pay attention to whether constants are opaque before doing the div by constant optimization. So BypassSlowDivision shouldn't introduce control flow that would make DAGCombiner unable to see an opaque constant. This can occur when a div and rem of the same constant are used in the same basic block. it will be hoisted, but not leave the block.
Longer term we probably need to look into the X86 immediate cost model used by constant hoisting and maybe not mark div/rem immediates for hoisting at all.
This fixes the case from PR38649.
Differential Revision: https://reviews.llvm.org/D51000
llvm-svn: 340303
b172b8884a