[all-commits] [llvm/llvm-project] 1cb47a: [CSSPGO] Unblock optimizations with pseudo probe i...

[Hongtao Yu via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 1cb47a063e2bbb04375ab52ed7377e8d555ef97d
      https://github.com/llvm/llvm-project/commit/1cb47a063e2bbb04375ab52ed7377e8d555ef97d
  Author: Hongtao Yu <hoy at fb.com>
  Date:   2021-02-10 (Wed, 10 Feb 2021)

  Changed paths:
    M llvm/include/llvm/CodeGen/MachineInstr.h
    M llvm/include/llvm/IR/Instruction.h
    M llvm/lib/CodeGen/LiveRangeShrink.cpp
    M llvm/lib/CodeGen/MachineInstr.cpp
    M llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
    M llvm/lib/CodeGen/StackProtector.cpp
    M llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
    M llvm/lib/IR/Instruction.cpp
    M llvm/lib/Transforms/IPO/FunctionAttrs.cpp
    M llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
    M llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
    A llvm/test/Transforms/SampleProfile/pseudo-probe-instcombine.ll
    A llvm/test/Transforms/SampleProfile/pseudo-probe-instsched.ll
    A llvm/test/Transforms/SampleProfile/pseudo-probe-peep.ll
    A llvm/test/Transforms/SampleProfile/pseudo-probe-twoaddr.ll

  Log Message:
  -----------
  [CSSPGO] Unblock optimizations with pseudo probe instrumentation.

The IR/MIR pseudo probe intrinsics don't get materialized into real machine instructions and therefore they don't incur runtime cost directly. However, they come with indirect cost by blocking certain optimizations. Some of the blocking are intentional (such as blocking code merge) for better counts quality while the others are accidental. This change unblocks perf-critical optimizations that do not affect counts quality. They include:

1. IR InstCombine, sinking load operation to shorten lifetimes.
2. MIR LiveRangeShrink, similar to #1
3. MIR TwoAddressInstructionPass, i.e, opeq transform
4. MIR function argument copy elision
5. IR stack protection. (though not perf-critical but nice to have).

Reviewed By: wmi

Differential Revision: https://reviews.llvm.org/D95982