[flang-commits] [flang] [flang] Lower REDUCE intrinsic with no DIM argument and rank 1 (PR #94652)

[via flang-commits]

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@@ -5705,7 +5705,63 @@ void IntrinsicLibrary::genRandomSeed(llvm::ArrayRef<fir::ExtendedValue> args) {
 fir::ExtendedValue
 IntrinsicLibrary::genReduce(mlir::Type resultType,
                             llvm::ArrayRef<fir::ExtendedValue> args) {
-  TODO(loc, "intrinsic: reduce");
+  assert(args.size() == 6);
+
+  fir::BoxValue arrayTmp = builder.createBox(loc, args[0]);
+  mlir::Value array = fir::getBase(arrayTmp);
+  mlir::Value operation = fir::getBase(args[1]);
+  int rank = arrayTmp.rank();
+  assert(rank >= 1);
+
+  mlir::Type ty = array.getType();
+  mlir::Type arrTy = fir::dyn_cast_ptrOrBoxEleTy(ty);
+  mlir::Type eleTy = mlir::cast<fir::SequenceType>(arrTy).getEleTy();
+
+  // Handle optional mask argument
+  bool absentDim = isStaticallyAbsent(args[1]);
+
+  auto mask = isStaticallyAbsent(args[3])
+                  ? builder.create<fir::AbsentOp>(
+                        loc, fir::BoxType::get(builder.getI1Type()))
+                  : builder.createBox(loc, args[3]);
+
+  mlir::Value identity =
+      isStaticallyAbsent(args[4])
+          ? builder.create<fir::AbsentOp>(loc, fir::ReferenceType::get(eleTy))
+          : fir::getBase(args[4]);
+
+  mlir::Value ordered = isStaticallyAbsent(args[5])
+                            ? builder.createBool(loc, true)
+                            : fir::getBase(args[5]);
+
+  // We call the type specific versions because the result is scalar
+  // in the case below.
+  if (absentDim || rank == 1) {
+    if (fir::isa_complex(eleTy) || fir::isa_derived(eleTy)) {
+      mlir::Value result = builder.createTemporary(loc, eleTy);
+      fir::runtime::genReduce(builder, loc, array, operation, mask, identity,
+                              ordered, result);
+      if (fir::isa_derived(eleTy))
+        return result;
+      return builder.create<fir::LoadOp>(loc, result);
+    }
+    if (fir::isa_char(eleTy)) {
+      // Create mutable fir.box to be passed to the runtime for the result.
+      fir::MutableBoxValue resultMutableBox =
+          fir::factory::createTempMutableBox(builder, loc, eleTy);
+      mlir::Value resultIrBox =
+          fir::factory::getMutableIRBox(builder, loc, resultMutableBox);
+      fir::runtime::genReduce(builder, loc, array, operation, mask, identity,
+                              ordered, resultIrBox);
+      // Handle cleanup of allocatable result descriptor and return
+      return readAndAddCleanUp(resultMutableBox, resultType, "REDUCE");
+    }
+    auto resultBox = builder.create<fir::AbsentOp>(
+        loc, fir::BoxType::get(builder.getI1Type()));
+    return fir::runtime::genReduce(builder, loc, array, operation, mask,
+                                   identity, ordered, resultBox);
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jeanPerier wrote:

I think passing a null mlir::Value here may just be better to allow the genReduce to assert that the box is here when it needs it and avoid creating unused IR in other cases.
Maybe even better to have two distinct fir::runtime API for these cases.

https://github.com/llvm/llvm-project/pull/94652