[MLIR] NFC. Introduce mlir::hasEffect and refactor usages dialect util

[bondhugula]

Summary

Introduce mlir::hasEffect and refactor existing usage to use utility.
NFC.

[bondhugula]

Update comment.

[arnab-oss]

I think this change alters the semantics, and won't work if the op has deallocate + some other effects on val. Those type of ops still qualify as dealloc ops.

[bondhugula]

In D132117#3738814, @arnab-oss wrote:

I think this change alters the semantics, and won't work if the op has deallocate + some other effects on val. Those type of ops still qualify as dealloc ops.

Yes, it does tighten the semantics. An op that has, say, a read effect and a dealloc effect on the same value will no longer be treated as a dealloc by this utility. We probably need to introduce hasEffect<....>(user, value) and use that.

[mehdi_amini]

We probably need to introduce hasEffect<....>(user, value) and use that.

This is basically the code implemented in-line right now, right?

[bondhugula]

In D132117#3739949, @mehdi_amini wrote:

We probably need to introduce hasEffect<....>(user, value) and use that.

This is basically the code implemented in-line right now, right?

Yes, that's exactly what it is.

[bondhugula]

In D132117#3739949, @mehdi_amini wrote:

We probably need to introduce hasEffect<....>(user, value) and use that.

This is basically the code implemented in-line right now, right?

Updated now @mehdi_amini PTAL, the new utlity.

[bondhugula]

Update to switch check to a new utility for the old code. This makes it NFC.

[arnab-oss]

LGTM
Thanks for implementing the suggested changes.

mlir/lib/Dialect/MemRef/IR/MemRefDialect.cpp

 void mlir::memref::MemRefDialect::initialize() {
   addOperations<
 #define GET_OP_LIST
 #include "mlir/Dialect/MemRef/IR/MemRefOps.cpp.inc"
       >();
   addInterfaces<MemRefInlinerInterface>();
 }
 
-/// Finds a single dealloc operation for the given allocated value.
+/// Finds the unique dealloc operation (if one exists) for `allocValue`.
 llvm::Optional<Operation *> mlir::memref::findDealloc(Value allocValue) {
   Operation *dealloc = nullptr;
   for (Operation *user : allocValue.getUsers()) {
-    auto effectInterface = dyn_cast<MemoryEffectOpInterface>(user);
-    if (!effectInterface)
-      continue;
-    // Try to find a free effect that is applied to one of our values
-    // that will be automatically freed by our pass.
-    SmallVector<MemoryEffects::EffectInstance, 2> effects;
-    effectInterface.getEffectsOnValue(allocValue, effects);
-    const bool isFree =
-        llvm::any_of(effects, [&](MemoryEffects::EffectInstance &it) {
-          return isa<MemoryEffects::Free>(it.getEffect());
-        });
-    if (!isFree)
+    if (!hasSingleEffect<MemoryEffects::Free>(user, allocValue))
       continue;
     // If we found > 1 dealloc, return None.
     if (dealloc)
       return llvm::None;
     dealloc = user;
   }
   return dealloc;
 }