[PATCH] D105700: [LoopSimplify] Convert loop with multiple latches to nested loop using dominator tree

[JinGu Kang via Phabricator via llvm-commits]

jaykang10 created this revision.
jaykang10 added reviewers: eli.friedman, sanwou01.
Herald added subscribers: pengfei, asbirlea, hiraditya.
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With certain condition of phi node, LoopSimplify pass converts loop with multiple latches to a nested loop as below.

  // Loop with multiple latches
  //
  //             |     /----------------\
  //    +--------v----v------+          |
  //    |      header        <---\      |
  //    +--------------------+   |      |
  //             |               |      |
  //    +--------v-----------+   |      |
  //    |      latch1        >---/      |
  //    +--------------------+          |
  //             |                      |
  //    +--------v-----------+          |
  //    |      latch2        >----------/
  //    +--------------------+
  //             |
  //==============================>
  //
  // A nested loop
  //
  //             |     /----------------\
  //    +-------------v------+          |
  //    |   outer header     |          |
  //    +--------------------+          |
  //             |                      |
  //    +--------v----v------+          |
  //    |   inner header     <---\      |
  //    +--------------------+   |      |
  //             |               |      |
  //    +--------v-----------+   |      |
  //    |      latch1        >---/      |
  //    +--------------------+          |
  //             |                      |
  //    +--------v-----------+          |
  //    |      latch2        >----------/
  //    +--------------------+
  //             |

This patch enables above transformation more using dominator tree. If one latch dominates other latches, the latch can be inner loop's one.


https://reviews.llvm.org/D105700

Files:
  llvm/lib/Transforms/Utils/LoopSimplify.cpp
  llvm/test/CodeGen/AArch64/aarch64-loop-gep-opt.ll
  llvm/test/CodeGen/X86/2008-04-28-CoalescerBug.ll
  llvm/test/CodeGen/X86/2009-02-26-MachineLICMBug.ll
  llvm/test/CodeGen/X86/bb_rotate.ll
  llvm/test/Transforms/IndVarSimplify/2011-10-27-lftrnull.ll
  llvm/test/Transforms/IndVarSimplify/rewrite-loop-exit-value.ll
  llvm/test/Transforms/LICM/hoist-mustexec.ll
  llvm/test/Transforms/LoopSimplifyCFG/constant-fold-branch.ll
  llvm/test/Transforms/LoopSimplifyCFG/update_parents.ll
  llvm/test/Transforms/LoopVectorize/loop-form.ll
  llvm/test/Transforms/LoopVectorize/loop-legality-checks.ll
  llvm/test/Transforms/LoopVectorize/skeleton-lcssa-crash.ll

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