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We currently always vectorize induction variables. However, if an induction variable is only used for counting loop iterations or computing addresses with getelementptr instructions, we don't need to do this. Vectorizing these trivial induction variables can create vector code that is difficult to simplify later on. This is especially true when the unroll factor is greater than one, and we create vector arithmetic when computing step vectors. With this patch, we check if an induction variable is only used for counting iterations or computing addresses, and if so, scalarize the arithmetic when computing step vectors instead. This allows for greater simplification. This patch addresses the suboptimal pointer arithmetic sequence seen in PR27881. Reference: https://llvm.org/bugs/show_bug.cgi?id=27881 Differential Revision: http://reviews.llvm.org/D21620 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@274627 91177308-0d34-0410-b5e6-96231b3b80d8