Definitions for FPU control.

1998-07-27 17:52:34 +00:00 · 1998-07-27 17:52:34 +00:00 · 2f601732bd
parent 22a7aa47a3
commit 2f601732bd
1 changed files with 93 additions and 0 deletions
--- a/sysdeps/arm/fpu/fpu_control.h
+++ b/sysdeps/arm/fpu/fpu_control.h
@ -0,0 +1,93 @@
+/* FPU control word definitions.  ARM version.
+   Copyright (C) 1996, 1997, 1998 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 Library General Public License as
+   published by the Free Software Foundation; either version 2 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If not,
+   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+#ifndef _FPU_CONTROL_H
+#define _FPU_CONTROL_H
+
+/* We have a slight terminology confusion here.  On the ARM, the register
+ * we're interested in is actually the FPU status word - the FPU control
+ * word is something different (which is implementation-defined and only
+ * accessible from supervisor mode.)  
+ *
+ * The FPSR looks like this:
+ *
+ *     31-24        23-16          15-8              7-0
+ * | system ID | trap enable | system control | exception flags | 
+ *
+ * We ignore the system ID bits; for interest's sake they are:
+ *
+ *  0000	"old" FPE
+ *  1000	FPPC hardware
+ *  0001	FPE 400
+ *  1001	FPA hardware
+ *
+ * The trap enable and exception flags are both structured like this:
+ *
+ *     7 - 5     4     3     2     1     0
+ * | reserved | INX | UFL | OFL | DVZ | IVO | 
+ *
+ * where a `1' bit in the enable byte means that the trap can occur, and
+ * a `1' bit in the flags byte means the exception has occurred.
+ *
+ * The exceptions are:
+ *
+ *  IVO - invalid operation
+ *  DVZ - divide by zero
+ *  OFL - overflow
+ *  UFL - underflow
+ *  INX - inexact (do not use; implementations differ)
+ *
+ * The system control byte looks like this:
+ *
+ *     7-5      4    3    2    1    0
+ * | reserved | AC | EP | SO | NE | ND |
+ * 
+ * where the bits mean
+ *
+ *  ND - no denormalised numbers (force them all to zero)
+ *  NE - enable NaN exceptions
+ *  SO - synchronous operation
+ *  EP - use expanded packed-decimal format
+ *  AC - use alternate definition for C flag on compare operations
+ */
+
+#define _FPU_RESERVED 0xfff0e0f0  /* These bits are reserved.  */
+
+/* The fdlibm code requires no interrupts for exceptions.  Don't
+   change the rounding mode, it would break long double I/O!  */
+#define _FPU_DEFAULT  0x00000000 /* Default value.  */
+
+/* Type of the control word.  */
+typedef unsigned int fpu_control_t;
+
+/* Macros for accessing the hardware control word.  */
+#define _FPU_GETCW(cw) __asm__ ("rfs %0" : "=r" (cw))
+#define _FPU_SETCW(cw) __asm__ ("wfs %0" : : "r" (cw))
+
+/* Default control word set at startup.  */
+extern fpu_control_t __fpu_control;
+
+__BEGIN_DECLS
+
+/* Called at startup.  It can be used to manipulate fpu control register.  */
+extern void __setfpucw __P ((fpu_control_t));
+
+__END_DECLS
+
+#endif /* _FPU_CONTROL_H */