[all-commits] [llvm/llvm-project] 10357e: [LoopUtils] Better accuracy for getLoopEstimatedTr...

[ebrevnov via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 10357e1c89b370a18500a8a8d69a68ab72db979e
      https://github.com/llvm/llvm-project/commit/10357e1c89b370a18500a8a8d69a68ab72db979e
  Author: Evgeniy Brevnov <evgueni.brevnov at gmail.com>
  Date:   2020-01-20 (Mon, 20 Jan 2020)

  Changed paths:
    M llvm/lib/Transforms/Utils/LoopUtils.cpp
    M llvm/test/Transforms/LoopUnroll/peel-loop-conditions-pgo-1.ll
    M llvm/test/Transforms/LoopUnroll/peel-loop-pgo-deopt-idom-2.ll
    M llvm/test/Transforms/LoopUnroll/peel-loop-pgo-deopt-idom.ll
    M llvm/test/Transforms/LoopUnroll/peel-loop-pgo-deopt.ll
    M llvm/test/Transforms/LoopUnroll/peel-loop-pgo.ll

  Log Message:
  -----------
  [LoopUtils] Better accuracy for getLoopEstimatedTripCount.

Summary: Current implementation of getLoopEstimatedTripCount returns 1 iteration less than it should. The reason is that in bottom tested loop first iteration is executed before first back branch is taken. For example for loop with !{!"branch_weights", i32 1 // taken, i32 1 // exit} metadata getLoopEstimatedTripCount gives 1 while actual number of iterations is 2.

Reviewers: Ayal, fhahn

Reviewed By: Ayal

Subscribers: mgorny, hiraditya, zzheng, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D71990