Changed return type to FailureOr<UnrolledLoopInfo>

mlir/include/mlir/Dialect/SCF/Utils/Utils.h

@@ -112,17 +112,17 @@ void collapseParallelLoops(RewriterBase &rewriter, scf::ParallelOp loops,
                            ArrayRef<std::vector<unsigned>> combinedDimensions);
 
 struct UnrolledLoopInfo {
-  scf::ForOp mainLoopOp;
-  scf::ForOp epilogueLoopOp;
+  scf::ForOp mainLoopOp = nullptr;
+  scf::ForOp epilogueLoopOp = nullptr;
 };
 
 /// Unrolls this for operation by the specified unroll factor. Returns the
 /// unrolled main loop and the eplilog loop, if the loop is unrolled. Otherwise
-/// returns a strucutre of null fields if the loop cannot be unrolled either due
-/// to restrictions or due to invalid unroll factors. Requires positive loop
-/// bounds and step. If specified, annotates the Ops in each unrolled iteration
-/// by applying `annotateFn`.
-UnrolledLoopInfo loopUnrollByFactor(
+/// returns failure if the loop cannot be unrolled either due to restrictions or
+/// due to invalid unroll factors. Requires positive loop bounds and step. If
+/// specified, annotates the Ops in each unrolled iteration by applying
+/// `annotateFn`.
+FailureOr<UnrolledLoopInfo> loopUnrollByFactor(
     scf::ForOp forOp, uint64_t unrollFactor,
     function_ref<void(unsigned, Operation *, OpBuilder)> annotateFn = nullptr);
 

mlir/lib/Dialect/SCF/TransformOps/SCFTransformOps.cpp

@@ -354,8 +354,7 @@ transform::LoopUnrollOp::applyToOne(transform::TransformRewriter &rewriter,
                                     transform::TransformState &state) {
   LogicalResult result(failure());
   if (scf::ForOp scfFor = dyn_cast<scf::ForOp>(op)) {
-    auto resultLoops = loopUnrollByFactor(scfFor, getFactor());
-    result = resultLoops.mainLoopOp ? success() : failure();
+    result = loopUnrollByFactor(scfFor, getFactor());
   } else if (AffineForOp affineFor = dyn_cast<AffineForOp>(op))
     result = loopUnrollByFactor(affineFor, getFactor());
   else

mlir/lib/Dialect/SCF/Utils/Utils.cpp

@@ -373,15 +373,15 @@ static void generateUnrolledLoop(
 }
 
 /// Unrolls 'forOp' by 'unrollFactor', returns the unrolled main loop and the
-/// eplilog loop, if the loop is unrolled. Otherwise return null.
-UnrolledLoopInfo mlir::loopUnrollByFactor(
+/// eplilog loop, if the loop is unrolled.
+FailureOr<UnrolledLoopInfo> mlir::loopUnrollByFactor(
     scf::ForOp forOp, uint64_t unrollFactor,
     function_ref<void(unsigned, Operation *, OpBuilder)> annotateFn) {
   assert(unrollFactor > 0 && "expected positive unroll factor");
 
   // Return if the loop body is empty.
   if (llvm::hasSingleElement(forOp.getBody()->getOperations()))
-    return {forOp, nullptr};
+    return UnrolledLoopInfo{forOp, nullptr};
 
   // Compute tripCount = ceilDiv((upperBound - lowerBound), step) and populate
   // 'upperBoundUnrolled' and 'stepUnrolled' for static and dynamic cases.
@@ -402,8 +402,8 @@ UnrolledLoopInfo mlir::loopUnrollByFactor(
     if (unrollFactor == 1) {
       if (*constTripCount == 1 &&
           failed(forOp.promoteIfSingleIteration(rewriter)))
-        return {nullptr, nullptr};
-      return {forOp, nullptr};
+        return failure();
+      return UnrolledLoopInfo{forOp, nullptr};
     }
 
     int64_t tripCountEvenMultiple =
@@ -470,8 +470,8 @@ UnrolledLoopInfo mlir::loopUnrollByFactor(
     }
     epilogueForOp->setOperands(epilogueForOp.getNumControlOperands(),
                                epilogueForOp.getInitArgs().size(), results);
-    (void)epilogueForOp.promoteIfSingleIteration(rewriter);
-    resultLoops.epilogueLoopOp = epilogueForOp;
+    if (epilogueForOp.promoteIfSingleIteration(rewriter).failed())
+      resultLoops.epilogueLoopOp = epilogueForOp;
   }
 
   // Create unrolled loop.
@@ -493,8 +493,8 @@ UnrolledLoopInfo mlir::loopUnrollByFactor(
       },
       annotateFn, iterArgs, yieldedValues);
   // Promote the loop body up if this has turned into a single iteration loop.
-  (void)forOp.promoteIfSingleIteration(rewriter);
-  resultLoops.mainLoopOp = forOp;
+  if (forOp.promoteIfSingleIteration(rewriter).failed())
+    resultLoops.mainLoopOp = forOp;
   return resultLoops;
 }