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authorPalmer Dabbelt <palmer@dabbelt.com>2018-01-29 09:27:10 -0800
committerPalmer Dabbelt <palmer@dabbelt.com>2018-01-29 10:26:43 -0800
commitb2cb5e0298e08b486190610a9e82356ccb6f564b (patch)
treec63e4d8b3e10d2df1af2424483a50f3ce7bee7a2 /sysdeps/riscv/rv64/rvd
parent67236aeb6e27bb6c975727f119e4b4f89e416706 (diff)
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RISC-V: Hard Float Support
This patch contains hardware floating-point support for the RISC-V ISA.
While we currently only support hard-float systems with both the F and D
extensions, I've left the F-specific code split out into seperate
folders in order to ease adding support for F-only and RV32I-based
systems in the future.  I gave this a quick once-over and believe I've
removed all the code that implements RV32IF, RV32IFD, and RV64IF
targets.

2018-01-29  Palmer Dabbelt  <palmer@sifive.com>

        * sysdeps/riscv/rv64/rvd/s_ceil.c: New file.
        * sysdeps/riscv/rv64/rvd/s_floor.c: Likewise.
        * sysdeps/riscv/rv64/rvd/s_llrint.c: Likewise.
        * sysdeps/riscv/rv64/rvd/s_llround.c: Likewise.
        * sysdeps/riscv/rv64/rvd/s_lrint.c: Likewise.
        * sysdeps/riscv/rv64/rvd/s_lround.c: Likewise.
        * sysdeps/riscv/rv64/rvd/s_nearbyint.c: Likewise.
        * sysdeps/riscv/rv64/rvd/s_rint.c: Likewise.
        * sysdeps/riscv/rv64/rvd/s_round.c: Likewise.
        * sysdeps/riscv/rv64/rvd/s_roundeven.c: Likewise.
        * sysdeps/riscv/rv64/rvd/s_trunc.c: Likewise.
        * sysdeps/riscv/rv64/rvf/s_llrintf.c: Likewise.
        * sysdeps/riscv/rv64/rvf/s_llroundf.c: Likewise.
        * sysdeps/riscv/rv64/rvf/s_lrintf.c: Likewise.
        * sysdeps/riscv/rv64/rvf/s_lroundf.c: Likewise.
        * sysdeps/riscv/rvd/e_sqrt.c: Likewise.
        * sysdeps/riscv/rvd/s_copysign.c: Likewise.
        * sysdeps/riscv/rvd/s_finite.c: Likewise.
        * sysdeps/riscv/rvd/s_fma.c: Likewise.
        * sysdeps/riscv/rvd/s_fmax.c: Likewise.
        * sysdeps/riscv/rvd/s_fmin.c: Likewise.
        * sysdeps/riscv/rvd/s_fpclassify.c: Likewise.
        * sysdeps/riscv/rvd/s_isinf.c: Likewise.
        * sysdeps/riscv/rvd/s_isnan.c: Likewise.
        * sysdeps/riscv/rvd/s_issignaling.c: Likewise.
        * sysdeps/riscv/rvf/e_sqrtf.c: Likewise.
        * sysdeps/riscv/rvf/fclrexcpt.c: Likewise.
        * sysdeps/riscv/rvf/fegetenv.c: Likewise.
        * sysdeps/riscv/rvf/fegetmode.c: Likewise.
        * sysdeps/riscv/rvf/fegetround.c: Likewise.
        * sysdeps/riscv/rvf/feholdexcpt.c: Likewise.
        * sysdeps/riscv/rvf/fesetenv.c: Likewise.
        * sysdeps/riscv/rvf/fesetexcept.c: Likewise.
        * sysdeps/riscv/rvf/fesetmode.c: Likewise.
        * sysdeps/riscv/rvf/fesetround.c: Likewise.
        * sysdeps/riscv/rvf/feupdateenv.c: Likewise.
        * sysdeps/riscv/rvf/fgetexcptflg.c: Likewise.
        * sysdeps/riscv/rvf/fraiseexcpt.c: Likewise.
        * sysdeps/riscv/rvf/fsetexcptflg.c: Likewise.
        * sysdeps/riscv/rvf/ftestexcept.c: Likewise.
        * sysdeps/riscv/rvf/get-rounding-mode.h: Likewise.
        * sysdeps/riscv/rvf/math_private.h: Likewise.
        * sysdeps/riscv/rvf/s_ceilf.c: Likewise.
        * sysdeps/riscv/rvf/s_copysignf.c: Likewise.
        * sysdeps/riscv/rvf/s_finitef.c: Likewise.
        * sysdeps/riscv/rvf/s_floorf.c: Likewise.
        * sysdeps/riscv/rvf/s_fmaf.c: Likewise.
        * sysdeps/riscv/rvf/s_fmaxf.c: Likewise.
        * sysdeps/riscv/rvf/s_fminf.c: Likewise.
        * sysdeps/riscv/rvf/s_fpclassifyf.c: Likewise.
        * sysdeps/riscv/rvf/s_isinff.c: Likewise.
        * sysdeps/riscv/rvf/s_isnanf.c: Likewise.
        * sysdeps/riscv/rvf/s_issignalingf.c: Likewise.
        * sysdeps/riscv/rvf/s_nearbyintf.c: Likewise.
        * sysdeps/riscv/rvf/s_rintf.c: Likewise.
        * sysdeps/riscv/rvf/s_roundevenf.c: Likewise.
        * sysdeps/riscv/rvf/s_roundf.c: Likewise.
        * sysdeps/riscv/rvf/s_truncf.c: Likewise.
Diffstat (limited to 'sysdeps/riscv/rv64/rvd')
-rw-r--r--sysdeps/riscv/rv64/rvd/s_ceil.c52
-rw-r--r--sysdeps/riscv/rv64/rvd/s_floor.c52
-rw-r--r--sysdeps/riscv/rv64/rvd/s_llrint.c30
-rw-r--r--sysdeps/riscv/rv64/rvd/s_llround.c30
-rw-r--r--sysdeps/riscv/rv64/rvd/s_lrint.c30
-rw-r--r--sysdeps/riscv/rv64/rvd/s_lround.c30
-rw-r--r--sysdeps/riscv/rv64/rvd/s_nearbyint.c52
-rw-r--r--sysdeps/riscv/rv64/rvd/s_rint.c52
-rw-r--r--sysdeps/riscv/rv64/rvd/s_round.c52
-rw-r--r--sysdeps/riscv/rv64/rvd/s_roundeven.c53
-rw-r--r--sysdeps/riscv/rv64/rvd/s_trunc.c52
11 files changed, 485 insertions, 0 deletions
diff --git a/sysdeps/riscv/rv64/rvd/s_ceil.c b/sysdeps/riscv/rv64/rvd/s_ceil.c
new file mode 100644
index 0000000000..af99ecca3d
--- /dev/null
+++ b/sysdeps/riscv/rv64/rvd/s_ceil.c
@@ -0,0 +1,52 @@
+/* ceil().  RISC-V version.
+   Copyright (C) 2017-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <math.h>
+#include <math_private.h>
+#include <libm-alias-double.h>
+#include <stdint.h>
+
+double
+__ceil (double x)
+{
+  int flags = riscv_getflags ();
+  bool nan = isnan (x);
+  double mag = fabs (x);
+
+  if (nan)
+    return x + x;
+
+  if (mag < (1ULL << __DBL_MANT_DIG__))
+    {
+      int64_t i;
+      double new_x;
+
+      asm volatile ("fcvt.l.d %0, %1, rup" : "=r" (i) : "f" (x));
+      asm volatile ("fcvt.d.l %0, %1, rup" : "=f" (new_x) : "r" (i));
+
+      /* ceil(-0) == -0, and in general we'll always have the same
+	 sign as our input.  */
+      x = copysign (new_x, x);
+
+      riscv_setflags (flags);
+    }
+
+  return x;
+}
+
+libm_alias_double (__ceil, ceil)
diff --git a/sysdeps/riscv/rv64/rvd/s_floor.c b/sysdeps/riscv/rv64/rvd/s_floor.c
new file mode 100644
index 0000000000..f34af98cce
--- /dev/null
+++ b/sysdeps/riscv/rv64/rvd/s_floor.c
@@ -0,0 +1,52 @@
+/* floor().  RISC-V version.
+   Copyright (C) 2017-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <math.h>
+#include <math_private.h>
+#include <libm-alias-double.h>
+#include <stdint.h>
+
+double
+__floor (double x)
+{
+  int flags = riscv_getflags ();
+  bool nan = isnan (x);
+  double mag = fabs (x);
+
+  if (nan)
+    return x + x;
+
+  if (mag < (1ULL << __DBL_MANT_DIG__))
+    {
+      int64_t i;
+      double new_x;
+
+      asm volatile ("fcvt.l.d %0, %1, rdn" : "=r" (i) : "f" (x));
+      asm volatile ("fcvt.d.l %0, %1, rdn" : "=f" (new_x) : "r" (i));
+
+      /* floor(-0) == -0, and in general we'll always have the same
+	 sign as our input.  */
+      x = copysign (new_x, x);
+
+      riscv_setflags (flags);
+    }
+
+  return x;
+}
+
+libm_alias_double (__floor, floor)
diff --git a/sysdeps/riscv/rv64/rvd/s_llrint.c b/sysdeps/riscv/rv64/rvd/s_llrint.c
new file mode 100644
index 0000000000..8f37090d74
--- /dev/null
+++ b/sysdeps/riscv/rv64/rvd/s_llrint.c
@@ -0,0 +1,30 @@
+/* llrint().  RISC-V version.
+   Copyright (C) 2017-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <libm-alias-double.h>
+#include <stdint.h>
+
+long long int
+__llrint (double x)
+{
+  int64_t res;
+  asm ("fcvt.l.d %0, %1" : "=r" (res) : "f" (x));
+  return res;
+}
+
+libm_alias_double (__llrint, llrint)
diff --git a/sysdeps/riscv/rv64/rvd/s_llround.c b/sysdeps/riscv/rv64/rvd/s_llround.c
new file mode 100644
index 0000000000..b7e448876b
--- /dev/null
+++ b/sysdeps/riscv/rv64/rvd/s_llround.c
@@ -0,0 +1,30 @@
+/* llround().  RISC-V version.
+   Copyright (C) 2017-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <libm-alias-double.h>
+#include <stdint.h>
+
+long long int
+__llround (double x)
+{
+  int64_t res;
+  asm ("fcvt.l.d %0, %1, rmm" : "=r" (res) : "f" (x));
+  return res;
+}
+
+libm_alias_double (__llround, llround)
diff --git a/sysdeps/riscv/rv64/rvd/s_lrint.c b/sysdeps/riscv/rv64/rvd/s_lrint.c
new file mode 100644
index 0000000000..48f61be966
--- /dev/null
+++ b/sysdeps/riscv/rv64/rvd/s_lrint.c
@@ -0,0 +1,30 @@
+/* lrint().  RISC-V version.
+   Copyright (C) 2017-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <libm-alias-double.h>
+#include <stdint.h>
+
+long int
+__lrint (double x)
+{
+  int64_t res;
+  asm ("fcvt.l.d %0, %1" : "=r" (res) : "f" (x));
+  return res;
+}
+
+libm_alias_double (__lrint, lrint)
diff --git a/sysdeps/riscv/rv64/rvd/s_lround.c b/sysdeps/riscv/rv64/rvd/s_lround.c
new file mode 100644
index 0000000000..392233cd04
--- /dev/null
+++ b/sysdeps/riscv/rv64/rvd/s_lround.c
@@ -0,0 +1,30 @@
+/* llround().  RISC-V version.
+   Copyright (C) 2017-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <libm-alias-double.h>
+#include <stdint.h>
+
+long int
+__lround (double x)
+{
+  int64_t res;
+  asm ("fcvt.l.d %0, %1, rmm" : "=r" (res) : "f" (x));
+  return res;
+}
+
+libm_alias_double (__lround, lround)
diff --git a/sysdeps/riscv/rv64/rvd/s_nearbyint.c b/sysdeps/riscv/rv64/rvd/s_nearbyint.c
new file mode 100644
index 0000000000..e17f038429
--- /dev/null
+++ b/sysdeps/riscv/rv64/rvd/s_nearbyint.c
@@ -0,0 +1,52 @@
+/* nearbyint().  RISC-V version.
+   Copyright (C) 2017-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <math.h>
+#include <math_private.h>
+#include <libm-alias-double.h>
+#include <stdint.h>
+
+double
+__nearbyint (double x)
+{
+  int flags = riscv_getflags ();
+  bool nan = isnan (x);
+  double mag = fabs (x);
+
+  if (nan)
+    return x + x;
+
+  if (mag < (1ULL << __DBL_MANT_DIG__))
+    {
+      int64_t i;
+      double new_x;
+
+      asm volatile ("fcvt.l.d %0, %1" : "=r" (i) : "f" (x));
+      asm volatile ("fcvt.d.l %0, %1" : "=f" (new_x) : "r" (i));
+
+      /* nearbyint(-0) == -0, and in general we'll always have the same
+	 sign as our input.  */
+      x = copysign (new_x, x);
+
+      riscv_setflags (flags);
+    }
+
+  return x;
+}
+
+libm_alias_double (__nearbyint, nearbyint)
diff --git a/sysdeps/riscv/rv64/rvd/s_rint.c b/sysdeps/riscv/rv64/rvd/s_rint.c
new file mode 100644
index 0000000000..ef2380ea7f
--- /dev/null
+++ b/sysdeps/riscv/rv64/rvd/s_rint.c
@@ -0,0 +1,52 @@
+/* rint().  RISC-V version.
+   Copyright (C) 2017-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <math.h>
+#include <math_private.h>
+#include <libm-alias-double.h>
+#include <stdint.h>
+
+double
+__rint (double x)
+{
+  bool nan;
+  double mag;
+
+  nan = isnan (x);
+  mag = fabs (x);
+
+  if (nan)
+    return x + x;
+
+  if (mag < (1ULL << __DBL_MANT_DIG__))
+    {
+      int64_t i;
+      double new_x;
+
+      asm ("fcvt.l.d %0, %1" : "=r" (i) : "f" (x));
+      asm ("fcvt.d.l %0, %1" : "=f" (new_x) : "r" (i));
+
+      /* rint(-0) == -0, and in general we'll always have the same
+	 sign as our input.  */
+      x = copysign (new_x, x);
+    }
+
+  return x;
+}
+
+libm_alias_double (__rint, rint)
diff --git a/sysdeps/riscv/rv64/rvd/s_round.c b/sysdeps/riscv/rv64/rvd/s_round.c
new file mode 100644
index 0000000000..22cff63e09
--- /dev/null
+++ b/sysdeps/riscv/rv64/rvd/s_round.c
@@ -0,0 +1,52 @@
+/* round().  RISC-V version.
+   Copyright (C) 2017-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <math.h>
+#include <math_private.h>
+#include <libm-alias-double.h>
+#include <stdint.h>
+
+double
+__round (double x)
+{
+  int flags = riscv_getflags ();
+  bool nan = isnan (x);
+  double mag = fabs (x);
+
+  if (nan)
+    return x + x;
+
+  if (mag < (1ULL << __DBL_MANT_DIG__))
+    {
+      int64_t i;
+      double new_x;
+
+      asm volatile ("fcvt.l.d %0, %1, rmm" : "=r" (i) : "f" (x));
+      asm volatile ("fcvt.d.l %0, %1, rmm" : "=f" (new_x) : "r" (i));
+
+      /* round(-0) == -0, and in general we'll always have the same
+	 sign as our input.  */
+      x = copysign (new_x, x);
+
+      riscv_setflags (flags);
+    }
+
+  return x;
+}
+
+libm_alias_double (__round, round)
diff --git a/sysdeps/riscv/rv64/rvd/s_roundeven.c b/sysdeps/riscv/rv64/rvd/s_roundeven.c
new file mode 100644
index 0000000000..26a0b2ded3
--- /dev/null
+++ b/sysdeps/riscv/rv64/rvd/s_roundeven.c
@@ -0,0 +1,53 @@
+/* Round to nearest integer value, rounding halfway cases to even.
+   Copyright (C) 2017-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <math.h>
+#include <math_private.h>
+#include <libm-alias-double.h>
+#include <stdint.h>
+
+double
+__roundeven (double x)
+{
+  int flags = riscv_getflags ();
+  bool nan = isnan (x);
+  double mag = fabs (x);
+
+  if (nan)
+    return x + x;
+
+  if (mag < (1ULL << __DBL_MANT_DIG__))
+    {
+      int64_t i;
+      double new_x;
+
+      asm volatile ("fcvt.l.d %0, %1, rne" : "=r" (i) : "f" (x));
+      asm volatile ("fcvt.d.l %0, %1, rne" : "=f" (new_x) : "r" (i));
+
+      /* roundeven(-0) == -0, and in general we'll always have the same
+	 sign as our input.  */
+      x = copysign (new_x, x);
+
+      riscv_setflags (flags);
+    }
+
+  return x;
+}
+
+hidden_def (__roundeven)
+libm_alias_double (__roundeven, roundeven)
diff --git a/sysdeps/riscv/rv64/rvd/s_trunc.c b/sysdeps/riscv/rv64/rvd/s_trunc.c
new file mode 100644
index 0000000000..a0f78e6cd1
--- /dev/null
+++ b/sysdeps/riscv/rv64/rvd/s_trunc.c
@@ -0,0 +1,52 @@
+/* trunc().  RISC-V version.
+   Copyright (C) 2017-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <math.h>
+#include <math_private.h>
+#include <libm-alias-double.h>
+#include <stdint.h>
+
+double
+__trunc (double x)
+{
+  int flags = riscv_getflags ();
+  bool nan = isnan (x);
+  double mag = fabs (x);
+
+  if (nan)
+    return x + x;
+
+  if (mag < (1ULL << __DBL_MANT_DIG__))
+    {
+      int64_t i;
+      double new_x;
+
+      asm volatile ("fcvt.l.d %0, %1, rtz" : "=r" (i) : "f" (x));
+      asm volatile ("fcvt.d.l %0, %1, rtz" : "=f" (new_x) : "r" (i));
+
+      /* trunc(-0) == -0, and in general we'll always have the same
+	 sign as our input.  */
+      x = copysign (new_x, x);
+
+      riscv_setflags (flags);
+    }
+
+  return x;
+}
+
+libm_alias_double (__trunc, trunc)