Make header work in C

enzyme/Enzyme/Runtime/EnzymeMPFR.h

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+//===- EnzymeMPFR.h - Implementation of forward and reverse pass generation==//
+//
+//                             Enzyme Project
+//
+// Part of the Enzyme 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
+//
+// If using this code in an academic setting, please cite the following:
+// @incollection{enzymeNeurips,
+// title = {Instead of Rewriting Foreign Code for Machine Learning,
+//          Automatically Synthesize Fast Gradients},
+// author = {Moses, William S. and Churavy, Valentin},
+// booktitle = {Advances in Neural Information Processing Systems 33},
+// year = {2020},
+// note = {To appear in},
+// }
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains easy to use wrappers around MPFR functions.
+//
+//===----------------------------------------------------------------------===//
+#ifndef __ENZYME_RUNTIME_ENZYME_MPFR__
+#define __ENZYME_RUNTIME_ENZYME_MPFR__
+
+#include <mpfr.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define __ENZYME_MPFR_BINOP(LLVM_OP_NAME, MPFR_FUNC_NAME, FROM_TYPE, RET,      \
+                            MPFR_GET, ARG1, MPFR_SET_ARG1, ARG2,               \
+                            MPFR_SET_ARG2, ROUNDING_MODE)                      \
+  __attribute__((weak)) RET __enzyme_mpfr_##FROM_TYPE_binop_##LLVM_OP_NAME(    \
+      ARG1 a, ARG2 b, int64_t exponent, int64_t significand) {                 \
+    mpfr_t ma, mb, mc;                                                         \
+    mpfr_init2(ma, significand);                                               \
+    mpfr_init2(mb, significand);                                               \
+    mpfr_init2(mc, significand);                                               \
+    mpfr_set_##MPFR_SET_ARG1(ma, a, ROUNDING_MODE);                            \
+    mpfr_set_##MPFR_SET_ARG1(mb, b, ROUNDING_MODE);                            \
+    mpfr_##MPFR_FUNC_NAME(mc, ma, mb, ROUNDING_MODE);                          \
+    RET c = mpfr_get_##MPFR_GET(mc, ROUNDING_MODE);                            \
+    mpfr_clear(ma);                                                            \
+    mpfr_clear(mb);                                                            \
+    mpfr_clear(mc);                                                            \
+    return c;                                                                  \
+  }
+
+#define __ENZYME_MPFR_DEFAULT_ROUNDING_MODE GMP_RNDN
+#define __ENZYME_MPFR_DBL_MANGLE 64_52
+#define __ENZYME_MPFR_DOUBLE_BINOP(LLVM_OP_NAME, MPFR_FUNC_NAME,               \
+                                   ROUNDING_MODE)                              \
+  __ENZYME_MPFR_BINOP(LLVM_OP_NAME, MPFR_FUNC_NAME, __ENZYME_MPFR_DBL_MANGLE,  \
+                      double, d, double, d, double, d, ROUNDING_MODE)
+#define __ENZYME_MPFR_DOUBLE_BINOP_DEFAULT_ROUNDING(LLVM_OP_NAME,              \
+                                                    MPFR_FUNC_NAME)            \
+  __ENZYME_MPFR_DOUBLE_BINOP(LLVM_OP_NAME, MPFR_FUNC_NAME,                     \
+                             __ENZYME_MPFR_DEFAULT_ROUNDING_MODE)
+
+__ENZYME_MPFR_DOUBLE_BINOP_DEFAULT_ROUNDING(fmul, mul)
+__ENZYME_MPFR_DOUBLE_BINOP_DEFAULT_ROUNDING(fadd, add)
+__ENZYME_MPFR_DOUBLE_BINOP_DEFAULT_ROUNDING(fdiv, div)
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // #ifndef __ENZYME_RUNTIME_ENZYME_MPFR__