[SimplifyIndVars] Ignore dead users
IndVarSimplify sometimes makes transforms basing on users that are trivially dead. In particular,
if DCE wasn't run before it, there may be a dead `sext/zext` in loop that will trigger widening
transforms, however it makes no sense to do it.
This patch teaches IndVarsSimplify ignore the mist trivial cases of that.
Differential Revision: https://reviews.llvm.org/D47974
Reviewed By: sanjoy
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@334567 91177308-0d34-0410-b5e6-96231b3b80d8
9 files changed