[all-commits] [llvm/llvm-project] 8f3ad1: [flang][Transforms] Add LiftSCFWhileToSCFFor pass

[Kareem Ergawy via All-commits]

  Branch: refs/heads/users/ergawy/lift-scf-while-to-scf-for
  Home:   https://github.com/llvm/llvm-project
  Commit: 8f3ad1f08e1d2ad8248f19a238660ff8d5fbe3d2
      https://github.com/llvm/llvm-project/commit/8f3ad1f08e1d2ad8248f19a238660ff8d5fbe3d2
  Author: ergawy <kareem.ergawy at gmail.com>
  Date:   2026-07-31 (Fri, 31 Jul 2026)

  Changed paths:
    M flang/include/flang/Optimizer/Transforms/Passes.td
    M flang/lib/Optimizer/Transforms/CMakeLists.txt
    A flang/lib/Optimizer/Transforms/LiftSCFWhileToSCFFor.cpp
    A flang/test/Fir/LiftSCFWhileToSCFFor/iv-next-body-use.mlir
    A flang/test/Fir/LiftSCFWhileToSCFFor/step-gt-one.mlir
    A flang/test/Fir/LiftSCFWhileToSCFFor/step-one.mlir
    A flang/test/Fir/LiftSCFWhileToSCFFor/two-iter-args.mlir

  Log Message:
  -----------
  [flang][Transforms] Add LiftSCFWhileToSCFFor pass

Introduces `--lift-scf-while-to-scf-for`, which walks every scf.while
produced by upstream `lift-cf-to-scf` and, when the canonical
"trip-counter + induction-variable" shape is recognized, rewrites the
loop as scf.for. Other loop-carried before-args are passed through as
iter_args. Loops that do not match (data-dependent updates, used
results, non-positive IV step, etc.) are left untouched and a
diagnostic is emitted to stderr.

Recognition collects a LoopInfo describing the loop:
 - trip counter: candidate the gating cmp uses, must have step -1
 - induction variable: the single non-trip affine recurrence, must
   have positive step (negative step bails for now)
 - iter_args: any other before-args that pass through unchanged

Rewrite materializes `ub_excl = ivInit + tripInit * ivStep` before
the scf.while, casts lb/ub/step to index (so the resulting scf.for
is compatible with downstream affine conversion), and clones the
body from the predicate scf.if's continues branch. The IV recurrence
result is remapped to `forIV + step` materialized at the top of the
body so cloned ops referencing the next-iteration value keep working.

Companion to lift-cf-to-scf for rebuilding counted loops from
recovered do-while loops.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply at anthropic.com>



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications