Simplify index expressions constructed in loop flattening - #51173 (#52882)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/52882
Test Plan:
Imported from OSS
build/bin/test_tensorexpr
Reviewed By: ZolotukhinM
Differential Revision: D26676150
Pulled By: huiguoo
fbshipit-source-id: e202e0c8610eb107558a3add8a6560a0cb97704a
