[flang-commits] [flang] [llvm] [mlir] [flang][OpenMP][OMPIRBuilder][mlir] Optionally pass reduction vars by ref (PR #84304)

[David Truby via flang-commits]

================
@@ -294,14 +322,41 @@ mlir::omp::ReductionDeclareOp ReductionProcessor::createReductionDecl(
   builder.setInsertionPointToEnd(&decl.getReductionRegion().back());
   mlir::Value op1 = decl.getReductionRegion().front().getArgument(0);
   mlir::Value op2 = decl.getReductionRegion().front().getArgument(1);
+  mlir::Value outAddr = op1;
+
+  op1 = builder.loadIfRef(loc, op1);
+  op2 = builder.loadIfRef(loc, op2);
 
   mlir::Value reductionOp =
       createScalarCombiner(builder, loc, redId, type, op1, op2);
-  builder.create<mlir::omp::YieldOp>(loc, reductionOp);
+  if (isByRef) {
+    builder.create<fir::StoreOp>(loc, reductionOp, outAddr);
+    builder.create<mlir::omp::YieldOp>(loc, outAddr);
+  } else {
+    builder.create<mlir::omp::YieldOp>(loc, reductionOp);
+  }
 
   return decl;
 }
 
+bool ReductionProcessor::doReductionByRef(
+    const llvm::SmallVectorImpl<mlir::Value> &reductionVars) {
+  if (reductionVars.empty())
+    return false;
+  if (forceByrefReduction)
+    return true;
+
+  for (mlir::Value reductionVar : reductionVars) {
+    if (auto declare =
+            mlir::dyn_cast<hlfir::DeclareOp>(reductionVar.getDefiningOp()))
+      reductionVar = declare.getMemref();
+
+    if (!fir::isa_trivial(fir::unwrapRefType(reductionVar.getType())))
+      return true;
----------------
DavidTruby wrote:

Does this imply that all reductions on a clause have to be by ref or by val? E.g. if we have an array reduction on the clause does that mean an integer reduction also changes to byref?

https://github.com/llvm/llvm-project/pull/84304