[all-commits] [llvm/llvm-project] 1bcb6a: [MBP] Enable duplicating return block to remove ju...

[weiguozhi via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 1bcb6a3da231ee3bcf8513880599b5d054f590a4
      https://github.com/llvm/llvm-project/commit/1bcb6a3da231ee3bcf8513880599b5d054f590a4
  Author: Guozhi Wei <carrot at google.com>
  Date:   2023-06-21 (Wed, 21 Jun 2023)

  Changed paths:
    M llvm/lib/CodeGen/MachineBlockPlacement.cpp
    M llvm/test/CodeGen/AArch64/aarch64-matrix-umull-smull.ll
    A llvm/test/CodeGen/Thumb/branch-to-return.ll
    M llvm/test/CodeGen/Thumb2/LowOverheadLoops/mve-float-loops.ll
    M llvm/test/CodeGen/Thumb2/mve-vecreduce-loops.ll

  Log Message:
  -----------
  [MBP] Enable duplicating return block to remove jump to return

Sometimes LLVM generates branch to return instruction, like PR63227.

It is because in function MachineBlockPlacement::canTailDuplicateUnplacedPreds
we avoid duplicating a BB into another already placed BB to prevent destroying
computed layout. But if the successor BB is a return block, duplicating it will
only reduce taken branches without hurt to any other branches.

Differential Revision: https://reviews.llvm.org/D153093