[mlir][linalg][bufferize][NFC] Simplify allocateBuffersForResults

[springerm]

Summary

Reuse getResultBuffer.

Nicolas: Please check if it is OK to use output directly instead of:

Value dimTensor = bvm.lookupOrDefault(output);

Depends On D110940

[nicolasvasilache]

this seems fine, I cannot remember the layering evolution that made me not reuse code.
Thanks for improving!

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

1619–1620

nit: wants

[nicolasvasilache]

In D110941#3042111, @nicolasvasilache wrote:

this seems fine, I cannot remember the layering evolution that made me not reuse code.
Thanks for improving!

Ah it's because you added that function to refactor stuff and avoid code duplication, makes sense!

[springerm]

rebase

[springerm]

rebase

[springerm]

rebase

[springerm]

address comments

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

 // Bufferization as simple BlockAndValueMapping rewrites.
 //===----------------------------------------------------------------------===//
 
 /// Return the result buffer (memref) for a given OpResult (tensor). Allocate
 /// a new buffer and copy over data from the existing buffer if out-of-place
 /// bufferization is necessary.
 static Value getResultBuffer(OpBuilder &b, OpResult result,
                              const BlockAndValueMapping &bvm,
-                             BufferizationAliasInfo &aliasInfo) {
+                             BufferizationAliasInfo &aliasInfo,
+                             bool skipCopy = false) {
   OpBuilder::InsertionGuard guard(b);
   Operation *op = result.getOwner();
   Optional<OpOperand *> maybeOperand = getAliasingOpOperand(result);
   assert(maybeOperand && "corresponding OpOperand not found");
   Value operand = (*maybeOperand)->get();
   Value operandBuffer = lookup(bvm, operand);
   assert(operandBuffer && "operand buffer not found");
 
   // If bufferizing out-of-place, allocate a new buffer.
   if (getInPlace(result) != InPlaceSpec::True) {
     Location loc = op->getLoc();
     // Allocate the result buffer.
     Value resultBuffer =
         createNewAllocDeallocPairForShapedValue(b, loc, operand, aliasInfo);
-    if (!isInitTensorOp(operand)) {
+    if (!skipCopy && !isInitTensorOp(operand)) {
       // Set insertion point now that potential alloc/dealloc are introduced.
       b.setInsertionPoint(op);
       b.create<CopyOp>(loc, operandBuffer, resultBuffer);
     }
     return resultBuffer;
   }
 
   // Bufferizing in-place. No need to allocate a new buffer.
   return operandBuffer;
 }
 
 /// Helper function for LinalgOp bufferization.
-/// Examines each result and determines whether it bufferizes inplace on an
-/// operand.
-/// If the opResult bufferizes inplace, just reuse the existing buffer.
-/// Otherwise allocate a new buffer to hold the result.
 /// When allocating a new buffer, analyze whether `op` want to read form that
-/// buffer. In such a case, insert a copy to ensure the newly allocated buffer
-/// is properly initialiazed.
+/// buffer. Only in that case, a copy of the result buffer may be needed.
 static void allocateBuffersForResults(OpBuilder &b, Location loc, LinalgOp op,
                                       SmallVectorImpl<Value> &resultBuffers,
                                       BlockAndValueMapping &bvm,
                                       BufferizationAliasInfo &aliasInfo) {
   // Take a guard before anything else.
   OpBuilder::InsertionGuard g(b);
   b.setInsertionPoint(op);
 
   // TODO: provide the proper interface to iterate on OpResults and get the
   // matching OpOperands.
   for (OpOperand *opOperand : op.getOutputOperands()) {
-    Value output = opOperand->get();
-    assert(output.getType().isa<TensorType>() && "expected tensor type");
-
-    // If output tensor is marked inPlace, just use the buffer.
-    // The following uses internal knowledge of the position of inplaceable
-    // operand / results.
     OpResult opResult = getInplaceableOpResult(*opOperand);
-    if (getInPlace(opResult) == InPlaceSpec::True) {
-      Value v = lookup(bvm, output);
-      assert(v && "missing buffer");
-      resultBuffers.push_back(v);
-      continue;
-    }
-
-    // Otherwise, `op` is not inplaceable and we need to allocate its result.
-    Value dimTensor = bvm.lookupOrDefault(output);
-    Value alloc =
-        createNewAllocDeallocPairForShapedValue(b, loc, dimTensor, aliasInfo);
-    resultBuffers.push_back(alloc);
-
-    // Additionally, if the output buffer is used, clone its value for now.
-    if (op.payloadUsesValueFromOperand(opOperand)) {
-      Value v = lookup(bvm, output);
-      b.create<CopyOp>(loc, v, alloc);
-    }
+    assert(opResult && "could not find correspond OpResult");
+    bool skipCopy = !op.payloadUsesValueFromOperand(opOperand);
+    Value resultBuffer = getResultBuffer(b, opResult, bvm, aliasInfo, skipCopy);
+    resultBuffers.push_back(resultBuffer);
   }
 
   if (op->getNumResults())
     map(bvm, op->getResults(), resultBuffers);
 }
 
 /// Generic conversion for any LinalgOp on tensors.
 static LogicalResult bufferize(OpBuilder &b, LinalgOp op,