[mlir][SideEffects] Replace HasNoSideEffect with the memory effect interfaces.

HasNoSideEffect can now be implemented using the MemoryEffectInterface, removing the need to check multiple things for the same information. This also removes an easy foot-gun for users as 'Operation::hasNoSideEffect' would ignore operations that dynamically, or recursively, have no side effects. This also leads to an immediate improvement in some of the existing users, such as DCE, now that they have access to more information.

Differential Revision: https://reviews.llvm.org/D76036

1 files changed, 9 insertions, 7 deletions

diff --git a/mlir/lib/Transforms/LoopInvariantCodeMotion.cpp b/mlir/lib/Transforms/LoopInvariantCodeMotion.cpp
index a452e33..7300948 100644
--- a/mlir/lib/Transforms/LoopInvariantCodeMotion.cpp
+++ b/mlir/lib/Transforms/LoopInvariantCodeMotion.cpp
@@ -49,16 +49,18 @@ static bool canBeHoisted(Operation *op,
   if (auto memInterface = dyn_cast<MemoryEffectOpInterface>(op)) {
     if (!memInterface.hasNoEffect())
       return false;
-  } else if (!op->hasNoSideEffect() &&
-             !op->hasTrait<OpTrait::HasRecursiveSideEffects>()) {
+    // If the operation doesn't have side effects and it doesn't recursively
+    // have side effects, it can always be hoisted.
+    if (!op->hasTrait<OpTrait::HasRecursiveSideEffects>())
+      return true;
+
+    // Otherwise, if the operation doesn't provide the memory effect interface
+    // and it doesn't have recursive side effects we treat it conservatively as
+    // side-effecting.
+  } else if (!op->hasTrait<OpTrait::HasRecursiveSideEffects>()) {
     return false;
   }
 
-  // If the operation doesn't have side effects and it doesn't recursively
-  // have side effects, it can always be hoisted.
-  if (!op->hasTrait<OpTrait::HasRecursiveSideEffects>())
-    return true;
-
   // Recurse into the regions for this op and check whether the contained ops
   // can be hoisted.
   for (auto &region : op->getRegions()) {