[all-commits] [llvm/llvm-project] e0ac08: [LoopUnroll] Consider convergence control tokens w...

[Sameer Sahasrabuddhe via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: e0ac087ff004f7a63ba64b9685f4f098d6ee54c5
      https://github.com/llvm/llvm-project/commit/e0ac087ff004f7a63ba64b9685f4f098d6ee54c5
  Author: Sameer Sahasrabuddhe <sameer.sahasrabuddhe at amd.com>
  Date:   2024-06-06 (Thu, 06 Jun 2024)

  Changed paths:
    M llvm/include/llvm/Analysis/CodeMetrics.h
    M llvm/include/llvm/Analysis/LoopInfo.h
    M llvm/include/llvm/IR/InstrTypes.h
    M llvm/include/llvm/IR/IntrinsicInst.h
    M llvm/include/llvm/Transforms/Utils/UnrollLoop.h
    M llvm/lib/Analysis/CodeMetrics.cpp
    M llvm/lib/Analysis/LoopInfo.cpp
    M llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
    M llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp
    M llvm/lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp
    M llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
    M llvm/lib/Transforms/Utils/LoopRotationUtils.cpp
    M llvm/lib/Transforms/Utils/LoopUnroll.cpp
    M llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
    A llvm/test/Transforms/LoopUnroll/convergent.controlled.ll

  Log Message:
  -----------
  [LoopUnroll] Consider convergence control tokens when unrolling (#91715)

- There is no restriction on a loop with controlled convergent
operations when
  the relevant tokens are defined and used within the loop.

- When a token defined outside a loop is used inside (also called a loop
convergence heart), unrolling is allowed only in the absence of
remainder or
  runtime checks.

- When a token defined inside a loop is used outside, such a loop is
said to be
"extended". This loop can only be unrolled by also duplicating the
extended part
  lying outside the loop. Such unrolling is disabled for now.

- Clean up loop hearts: When unrolling a loop with a heart, duplicating
the
heart will introduce multiple static uses of a convergence control token
in a
cycle that does not contain its definition. This violates the static
rules for
tokens, and needs to be cleaned up into a single occurrence of the
intrinsic.

- Spell out the initializer for UnrollLoopOptions to improve
readability.


Original implementation [D85605] by Nicolai Haehnle
<nicolai.haehnle at amd.com>.



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