[flang] reduction fix from JanL (llvm#1565)

npsdb passed all but one test in smoke-fort  flang-463690 which is moved to smoke-fort-dev

Author: ronlieb

mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp

@@ -4961,12 +4961,18 @@ static uint64_t getTypeByteSize(mlir::Type type, const DataLayout &dl) {
 template <typename OpTy>
 static uint64_t getReductionDataSize(OpTy &op) {
   if (op.getNumReductionVars() > 0) {
-    assert(op.getNumReductionVars() == 1 &&
-           "Only 1 reduction variable currently supported");
-    mlir::Type reductionVarTy = op.getReductionVars()[0].getType();
+    SmallVector<omp::DeclareReductionOp> reductions;
+    collectReductionDecls(op, reductions);
+
+    llvm::SmallVector<mlir::Type> members;
+    for (omp::DeclareReductionOp &red : reductions) {
+      members.push_back(red.getType());
+    }
     Operation *opp = op.getOperation();
+    auto structType = mlir::LLVM::LLVMStructType::getLiteral(
+        opp->getContext(), members, /*isPacked=*/false);
     DataLayout dl = DataLayout(opp->getParentOfType<ModuleOp>());
-    return getTypeByteSize(reductionVarTy, dl);
+    return getTypeByteSize(structType, dl);
   }
   return 0;
 }
@@ -5062,8 +5068,6 @@ initTargetDefaultAttrs(omp::TargetOp targetOp, Operation *capturedOp,
       (maxThreadsVal >= 0 && maxThreadsVal < combinedMaxThreadsVal))
     combinedMaxThreadsVal = maxThreadsVal;
 
-  // Calculate reduction data size, limited to single reduction variable for
-  // now.
   int32_t reductionDataSize = 0;
   if (isGPU && capturedOp) {
     if (auto teamsOp = castOrGetParentOfType<omp::TeamsOp>(capturedOp))