Revert "[mlir] Refactor LICM into a utility"

This reverts commit 3131f80.

This commit broke the Windows mlir bot:
https://lab.llvm.org/buildbot/#/builders/13/builds/19745

mlir/include/mlir/IR/Region.h

@@ -341,12 +341,6 @@ class RegionRange
   RegionRange(Arg &&arg)
       : RegionRange(ArrayRef<std::unique_ptr<Region>>(std::forward<Arg>(arg))) {
   }
-  template <typename Arg>
-  RegionRange(Arg &&arg,
-              typename std::enable_if_t<
-                  std::is_constructible<ArrayRef<Region *>, Arg>::value &&
-                  !std::is_convertible<Arg, Region *>::value> * = nullptr)
-      : RegionRange(ArrayRef<Region *>(std::forward<Arg>(arg))) {}
   RegionRange(ArrayRef<std::unique_ptr<Region>> regions);
   RegionRange(ArrayRef<Region *> regions);
 

mlir/include/mlir/Interfaces/LoopLikeInterface.h

@@ -15,7 +15,20 @@
 
 #include "mlir/IR/OpDefinition.h"
 
+//===----------------------------------------------------------------------===//
+// LoopLike Interfaces
+//===----------------------------------------------------------------------===//
+
 /// Include the generated interface declarations.
 #include "mlir/Interfaces/LoopLikeInterface.h.inc"
 
+//===----------------------------------------------------------------------===//
+// LoopLike Utilities
+//===----------------------------------------------------------------------===//
+
+namespace mlir {
+/// Move loop invariant code out of a `looplike` operation.
+void moveLoopInvariantCode(LoopLikeOpInterface looplike);
+} // namespace mlir
+
 #endif // MLIR_INTERFACES_LOOPLIKEINTERFACE_H_

mlir/include/mlir/Transforms/ControlFlowSinkUtils.h

@@ -17,7 +17,6 @@ class DominanceInfo;
 class Operation;
 class Region;
 class RegionBranchOpInterface;
-class RegionRange;
 
 /// Given a list of regions, perform control flow sinking on them. For each
 /// region, control-flow sinking moves operations that dominate the region but
@@ -62,7 +61,7 @@ class RegionRange;
 ///
 /// Returns the number of operations sunk.
 size_t
-controlFlowSink(RegionRange regions, DominanceInfo &domInfo,
+controlFlowSink(ArrayRef<Region *> regions, DominanceInfo &domInfo,
                 function_ref<bool(Operation *, Region *)> shouldMoveIntoRegion,
                 function_ref<void(Operation *, Region *)> moveIntoRegion);
 

mlir/lib/Dialect/Linalg/Transforms/Hoisting.cpp

@@ -26,7 +26,6 @@
 #include "mlir/IR/BuiltinOps.h"
 #include "mlir/IR/Dominance.h"
 #include "mlir/Transforms/GreedyPatternRewriteDriver.h"
-#include "mlir/Transforms/LoopInvariantCodeMotionUtils.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Debug.h"
 

mlir/lib/Dialect/Linalg/Transforms/LinalgStrategyPasses.cpp

@@ -31,7 +31,6 @@
 #include "mlir/Pass/PassManager.h"
 #include "mlir/Support/LLVM.h"
 #include "mlir/Transforms/GreedyPatternRewriteDriver.h"
-#include "mlir/Transforms/LoopInvariantCodeMotionUtils.h"
 #include "mlir/Transforms/Passes.h"
 
 using namespace mlir;

mlir/lib/Interfaces/CMakeLists.txt

@@ -40,4 +40,17 @@ add_mlir_interface_library(SideEffectInterfaces)
 add_mlir_interface_library(TilingInterface)
 add_mlir_interface_library(VectorInterfaces)
 add_mlir_interface_library(ViewLikeInterface)
-add_mlir_interface_library(LoopLikeInterface)
+
+add_mlir_library(MLIRLoopLikeInterface
+  LoopLikeInterface.cpp
+
+  ADDITIONAL_HEADER_DIRS
+  ${MLIR_MAIN_INCLUDE_DIR}/mlir/Interfaces
+
+  DEPENDS
+  MLIRLoopLikeInterfaceIncGen
+
+  LINK_LIBS PUBLIC
+  MLIRIR
+  MLIRSideEffectInterfaces
+  )

mlir/lib/Interfaces/LoopLikeInterface.cpp

@@ -7,8 +7,108 @@
 //===----------------------------------------------------------------------===//
 
 #include "mlir/Interfaces/LoopLikeInterface.h"
+#include "mlir/Interfaces/SideEffectInterfaces.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/Support/Debug.h"
+#include <queue>
 
 using namespace mlir;
 
+#define DEBUG_TYPE "loop-like"
+
+//===----------------------------------------------------------------------===//
+// LoopLike Interfaces
+//===----------------------------------------------------------------------===//
+
 /// Include the definitions of the loop-like interfaces.
 #include "mlir/Interfaces/LoopLikeInterface.cpp.inc"
+
+//===----------------------------------------------------------------------===//
+// LoopLike Utilities
+//===----------------------------------------------------------------------===//
+
+/// Returns true if the given operation is side-effect free as are all of its
+/// nested operations.
+///
+/// TODO: There is a duplicate function in ControlFlowSink. Move
+/// `moveLoopInvariantCode` to TransformUtils and then factor out this function.
+static bool isSideEffectFree(Operation *op) {
+  if (auto memInterface = dyn_cast<MemoryEffectOpInterface>(op)) {
+    // If the op has side-effects, it cannot be moved.
+    if (!memInterface.hasNoEffect())
+      return false;
+    // If the op does not have recursive side effects, then it can be moved.
+    if (!op->hasTrait<OpTrait::HasRecursiveSideEffects>())
+      return true;
+  } else if (!op->hasTrait<OpTrait::HasRecursiveSideEffects>()) {
+    // Otherwise, if the op does not implement the memory effect interface and
+    // it does not have recursive side effects, then it cannot be known that the
+    // op is moveable.
+    return false;
+  }
+
+  // Recurse into the regions and ensure that all nested ops can also be moved.
+  for (Region &region : op->getRegions())
+    for (Operation &op : region.getOps())
+      if (!isSideEffectFree(&op))
+        return false;
+  return true;
+}
+
+/// Checks whether the given op can be hoisted by checking that
+/// - the op and none of its contained operations depend on values inside of the
+///   loop (by means of calling definedOutside).
+/// - the op has no side-effects.
+static bool canBeHoisted(Operation *op,
+                         function_ref<bool(Value)> definedOutside) {
+  if (!isSideEffectFree(op))
+    return false;
+
+  // Do not move terminators.
+  if (op->hasTrait<OpTrait::IsTerminator>())
+    return false;
+
+  // Walk the nested operations and check that all used values are either
+  // defined outside of the loop or in a nested region, but not at the level of
+  // the loop body.
+  auto walkFn = [&](Operation *child) {
+    for (Value operand : child->getOperands()) {
+      // Ignore values defined in a nested region.
+      if (op->isAncestor(operand.getParentRegion()->getParentOp()))
+        continue;
+      if (!definedOutside(operand))
+        return WalkResult::interrupt();
+    }
+    return WalkResult::advance();
+  };
+  return !op->walk(walkFn).wasInterrupted();
+}
+
+void mlir::moveLoopInvariantCode(LoopLikeOpInterface looplike) {
+  Region *loopBody = &looplike.getLoopBody();
+
+  std::queue<Operation *> worklist;
+  // Add top-level operations in the loop body to the worklist.
+  for (Operation &op : loopBody->getOps())
+    worklist.push(&op);
+
+  auto definedOutside = [&](Value value) {
+    return looplike.isDefinedOutsideOfLoop(value);
+  };
+
+  while (!worklist.empty()) {
+    Operation *op = worklist.front();
+    worklist.pop();
+    // Skip ops that have already been moved. Check if the op can be hoisted.
+    if (op->getParentRegion() != loopBody || !canBeHoisted(op, definedOutside))
+      continue;
+
+    looplike.moveOutOfLoop(op);
+
+    // Since the op has been moved, we need to check its users within the
+    // top-level of the loop body.
+    for (Operation *user : op->getUsers())
+      if (user->getParentRegion() == loopBody)
+        worklist.push(user);
+  }
+}

mlir/lib/Transforms/ControlFlowSink.cpp

@@ -19,7 +19,6 @@
 #include "mlir/Interfaces/SideEffectInterfaces.h"
 #include "mlir/Transforms/ControlFlowSinkUtils.h"
 #include "mlir/Transforms/Passes.h"
-#include "mlir/Transforms/SideEffectUtils.h"
 
 using namespace mlir;
 
@@ -30,6 +29,31 @@ struct ControlFlowSink : public ControlFlowSinkBase<ControlFlowSink> {
 };
 } // end anonymous namespace
 
+/// Returns true if the given operation is side-effect free as are all of its
+/// nested operations.
+static bool isSideEffectFree(Operation *op) {
+  if (auto memInterface = dyn_cast<MemoryEffectOpInterface>(op)) {
+    // If the op has side-effects, it cannot be moved.
+    if (!memInterface.hasNoEffect())
+      return false;
+    // If the op does not have recursive side effects, then it can be moved.
+    if (!op->hasTrait<OpTrait::HasRecursiveSideEffects>())
+      return true;
+  } else if (!op->hasTrait<OpTrait::HasRecursiveSideEffects>()) {
+    // Otherwise, if the op does not implement the memory effect interface and
+    // it does not have recursive side effects, then it cannot be known that the
+    // op is moveable.
+    return false;
+  }
+
+  // Recurse into the regions and ensure that all nested ops can also be moved.
+  for (Region &region : op->getRegions())
+    for (Operation &op : region.getOps())
+      if (!isSideEffectFree(&op))
+        return false;
+  return true;
+}
+
 void ControlFlowSink::runOnOperation() {
   auto &domInfo = getAnalysis<DominanceInfo>();
   getOperation()->walk([&](RegionBranchOpInterface branch) {

mlir/lib/Transforms/LoopInvariantCodeMotion.cpp

@@ -11,10 +11,15 @@
 //===----------------------------------------------------------------------===//
 
 #include "PassDetail.h"
+#include "mlir/IR/Builders.h"
 #include "mlir/Interfaces/LoopLikeInterface.h"
-#include "mlir/Transforms/LoopInvariantCodeMotionUtils.h"
+#include "mlir/Interfaces/SideEffectInterfaces.h"
 #include "mlir/Transforms/Passes.h"
-#include "mlir/Transforms/SideEffectUtils.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+
+#define DEBUG_TYPE "licm"
 
 using namespace mlir;
 
@@ -30,8 +35,10 @@ void LoopInvariantCodeMotion::runOnOperation() {
   // Walk through all loops in a function in innermost-loop-first order. This
   // way, we first LICM from the inner loop, and place the ops in
   // the outer loop, which in turn can be further LICM'ed.
-  getOperation()->walk(
-      [&](LoopLikeOpInterface loopLike) { moveLoopInvariantCode(loopLike); });
+  getOperation()->walk([&](LoopLikeOpInterface loopLike) {
+    LLVM_DEBUG(loopLike.print(llvm::dbgs() << "\nOriginal loop:\n"));
+    moveLoopInvariantCode(loopLike);
+  });
 }
 
 std::unique_ptr<Pass> mlir::createLoopInvariantCodeMotionPass() {

mlir/lib/Transforms/Utils/CMakeLists.txt

@@ -4,15 +4,12 @@ add_mlir_library(MLIRTransformUtils
   FoldUtils.cpp
   GreedyPatternRewriteDriver.cpp
   InliningUtils.cpp
-  LoopInvariantCodeMotionUtils.cpp
   RegionUtils.cpp
-  SideEffectUtils.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${MLIR_MAIN_INCLUDE_DIR}/mlir/Transforms
 
   LINK_LIBS PUBLIC
   MLIRAnalysis
-  MLIRLoopLikeInterface
   MLIRRewrite
   )