[flang-commits] [flang] [flang][runtime] Runtime support for REDUCE() (PR #86214)

[Slava Zakharin via flang-commits]

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@@ -0,0 +1,254 @@
+//===-- include/flang/Runtime/reduce.h --------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Defines the API for implementations of the transformational intrinsic
+// functionREDUCE(); see F'2023 16.9.173.
+//
+// Similar to the definition of the APIs for SUM(), &c., in reduction.h,
+// there are typed functions here like ReduceInteger4() for total reductions
+// to scalars and void functions like ReduceInteger4Dim() for partial
+// reductions to smaller arrays.
+
+#ifndef FORTRAN_RUNTIME_REDUCE_H_
+#define FORTRAN_RUNTIME_REDUCE_H_
+
+#include "flang/Common/float128.h"
+#include "flang/Common/uint128.h"
+#include "flang/Runtime/cpp-type.h"
+#include "flang/Runtime/entry-names.h"
+#include <complex>
+#include <cstdint>
+
+namespace Fortran::runtime {
+
+class Descriptor;
+
+template <typename T> using ReductionOperation = T (*)(const T *, const T *);
+template <typename CHAR>
+using ReductionCharOperation = void (*)(CHAR *hiddenResult, const CHAR *x,
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vzakhari wrote:

Should we follow the ABI used by Flang for regular `character(*) function (character(*), character(*))`? In this case the `resultLen` should be the second argument.

https://github.com/llvm/llvm-project/pull/86214