arm: add fenv support from glibc

1 files changed, 44 insertions, 0 deletions

diff --git a/libm/arm/fesetmode.c b/libm/arm/fesetmode.c
new file mode 100644
index 000000000..7919022b0
--- /dev/null
+++ b/libm/arm/fesetmode.c
@@ -0,0 +1,44 @@
+/* Install given floating-point control modes.  ARM version.
+   Copyright (C) 2016-2025 Free Software Foundation, Inc.
+
+   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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <fenv.h>
+#include <fpu_control.h>
+#include "arm-features.h"
+
+/* NZCV flags, QC bit, IDC bit and bits for IEEE exception status.  */
+#define FPU_STATUS_BITS 0xf800009f
+
+int
+fesetmode (const femode_t *modep)
+{
+  fpu_control_t fpscr, new_fpscr;
+
+  if (!ARM_HAVE_VFP)
+    /* Nothing to do.  */
+    return 0;
+
+  _FPU_GETCW (fpscr);
+  if (modep == FE_DFL_MODE)
+    new_fpscr = (fpscr & (_FPU_RESERVED | FPU_STATUS_BITS)) | _FPU_DEFAULT;
+  else
+    new_fpscr = (fpscr & FPU_STATUS_BITS) | (*modep & ~FPU_STATUS_BITS);
+
+  if (((new_fpscr ^ fpscr) & ~_FPU_MASK_NZCV) != 0)
+    _FPU_SETCW (new_fpscr);
+
+  return 0;
+}