Added support for context switching the data used by the gcc m68k

software floating point emulation code.  Code implemented by
Karen Sara Looney <Karen.Looney@colorado.edu> with much
email assistance from Joel.

c/src/exec/rtems/headers/attr.h

@@ -47,7 +47,7 @@ typedef unsigned32 rtems_attribute;
 #define RTEMS_NO_PRIORITY_CEILING 0x00000000
 #define RTEMS_PRIORITY_CEILING    0x00000040
 
-#if ( CPU_HARDWARE_FP == TRUE )
+#if ( CPU_HARDWARE_FP == TRUE ) || ( CPU_SOFTWARE_FP == TRUE )
 #define ATTRIBUTES_NOT_SUPPORTED       0
 #else
 #define ATTRIBUTES_NOT_SUPPORTED       RTEMS_FLOATING_POINT

c/src/exec/rtems/include/rtems/rtems/attr.h

@@ -47,7 +47,7 @@ typedef unsigned32 rtems_attribute;
 #define RTEMS_NO_PRIORITY_CEILING 0x00000000
 #define RTEMS_PRIORITY_CEILING    0x00000040
 
-#if ( CPU_HARDWARE_FP == TRUE )
+#if ( CPU_HARDWARE_FP == TRUE ) || ( CPU_SOFTWARE_FP == TRUE )
 #define ATTRIBUTES_NOT_SUPPORTED       0
 #else
 #define ATTRIBUTES_NOT_SUPPORTED       RTEMS_FLOATING_POINT

c/src/exec/score/cpu/m68k/cpu.c

@@ -177,3 +177,32 @@ const unsigned char __BFFFOtable[256] = {
     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
 };
 #endif
+
+/*PAGE
+ *
+ *  The following code context switches the software FPU emulation
+ *  code provided with GCC.
+ */
+
+#if (CPU_SOFTWARE_FP == TRUE)
+extern Context_Control_fp _fpCCR;
+
+void CPU_Context_save_fp (void **fp_context_ptr)
+{
+  Context_Control_fp *fp;
+
+  fp = (Context_Control_fp *) *fp_context_ptr;
+
+  *fp = _fpCCR;
+}
+
+void CPU_Context_restore_fp (void **fp_context_ptr)
+{
+  Context_Control_fp *fp;
+
+  fp = (Context_Control_fp *) *fp_context_ptr;
+
+  _fpCCR = *fp;
+}
+#endif
+

c/src/exec/score/cpu/m68k/cpu.h

@@ -52,12 +52,22 @@ extern "C" {
 /*
  *  Some family members have no FP, some have an FPU such as the
  *  MC68881/MC68882 for the MC68020, others have it built in (MC68030, 040).
+ *
+ *  NOTE:  If on a CPU without hardware FP, then one can use software
+ *         emulation.  The gcc software FP emulation code has data which
+ *         must be contexted switched on a per task basis.
  */
 
 #if ( M68K_HAS_FPU == 1 )
 #define CPU_HARDWARE_FP     TRUE
+#define CPU_SOFTWARE_FP     FALSE
 #else
 #define CPU_HARDWARE_FP     FALSE
+#if defined(__GCC__)
+#define CPU_SOFTWARE_FP     TRUE
+#else
+#define CPU_SOFTWARE_FP     FALSE
+#endif
 #endif
 
 /*
@@ -107,6 +117,38 @@ typedef struct {
   void       *a7_msp;            /* (a7) master stack pointer */
 }   Context_Control;
 
+/*
+ *  Floating point context ares
+ */
+
+#if (CPU_SOFTWARE_FP == TRUE)
+
+/*
+ *  This is the same as gcc's view of the software FP condition code
+ *  register _fpCCR.  The implementation of the emulation code is
+ *  in the gcc-VERSION/config/m68k directory.  This structure is
+ *  correct as of gcc 2.7.2.2.
+ */
+
+typedef struct {
+  unsigned16   _exception_bits;
+  unsigned16   _trap_enable_bits;
+  unsigned16   _sticky_bits;
+  unsigned16   _rounding_mode;
+  unsigned16   _format;
+  unsigned16   _last_operation;
+  union {
+    float sf;
+    double df;
+  } _operand1;
+  union {
+    float sf;
+    double df;
+  } _operand2;
+} Context_Control_fp;
+
+#else 
+
 /*
  *  FP context save area for the M68881/M68882 numeric coprocessors.
  */
@@ -117,6 +159,7 @@ typedef struct {
                                     /*    12 bytes for FMOVEM CREGS      */
                                     /*     4 bytes for non-null flag     */
 } Context_Control_fp;
+#endif
 
 /*
  *  The following structure defines the set of information saved
@@ -291,6 +334,34 @@ unsigned32 _CPU_ISR_Get_level( void );
         : "0" ((_the_context)->sr), "1" ((_the_context)->a7_msp) ); \
   }
 
+/*
+ *  Floating Point Context Area Support routines
+ */
+
+#if (CPU_SOFTWARE_FP == TRUE)
+
+/*
+ *  This software FP implementation is only for GCC.
+ */
+
+#define _CPU_Context_Fp_start( _base, _offset ) \
+   ((void *) _Addresses_Add_offset( (_base), (_offset) ) )
+
+
+#define _CPU_Context_Initialize_fp( _fp_area ) \
+   { \
+   Context_Control_fp *_fp; \
+   _fp = *(Context_Control_fp **)_fp_area; \
+   _fp->_exception_bits = 0; \
+   _fp->_trap_enable_bits = 0; \
+   _fp->_sticky_bits = 0; \
+   _fp->_rounding_mode = 0;  /* ROUND_TO_NEAREST */ \
+   _fp->_format = 0;         /* NIL */ \
+   _fp->_last_operation = 0;  /* NOOP */ \
+   _fp->_operand1.df = 0; \
+   _fp->_operand2.df = 0; \
+   }
+#else
 #define _CPU_Context_Fp_start( _base, _offset ) \
    ((void *) \
      _Addresses_Add_offset( \
@@ -305,6 +376,7 @@ unsigned32 _CPU_ISR_Get_level( void );
      *(--(_fp_context)) = 0; \
      *(_fp_area) = (unsigned8 *)(_fp_context); \
    }
+#endif
 
 /* end of Context handler macros */
 

c/src/exec/score/cpu/m68k/cpu_asm.s

@@ -51,8 +51,14 @@ restore:  movml    a0@,d1-d7/a2-a7     | restore context
  *
  *         CPU_FP_CONTEXT_SIZE is higher than expected to account for the
  *         -1 pushed at end of this sequence.
+ *
+ *         Neither of these entries is required if we have software FPU
+ *         emulation.  But if we don't have an FPU or emulation, then
+ *         we need the stub versions of these routines.
  */
 
+#if (CPU_SOFTWARE_FP == FALSE)
+
 .set FPCONTEXT_ARG,   4                    | save FP context argument
 
         .align  4
@@ -86,6 +92,7 @@ norst:  frestore a0@+                     | restore the fp state frame
         movl     a0,a1@                   | save pointer to saved context
 #endif
         rts
+#endif
 
 /*PAGE
  *  void _ISR_Handler()

c/src/exec/score/src/thread.c

@@ -212,7 +212,7 @@ void _Thread_Start_multitasking( void )
     */
  
 
-#if ( CPU_HARDWARE_FP == TRUE )
+#if ( CPU_HARDWARE_FP == TRUE ) || ( CPU_SOFTWARE_FP == TRUE )
    /*
     *  don't need to worry about saving BSP's floating point state
     */

cpukit/rtems/include/rtems/rtems/attr.h

@@ -47,7 +47,7 @@ typedef unsigned32 rtems_attribute;
 #define RTEMS_NO_PRIORITY_CEILING 0x00000000
 #define RTEMS_PRIORITY_CEILING    0x00000040
 
-#if ( CPU_HARDWARE_FP == TRUE )
+#if ( CPU_HARDWARE_FP == TRUE ) || ( CPU_SOFTWARE_FP == TRUE )
 #define ATTRIBUTES_NOT_SUPPORTED       0
 #else
 #define ATTRIBUTES_NOT_SUPPORTED       RTEMS_FLOATING_POINT

cpukit/score/cpu/m68k/cpu.c

@@ -177,3 +177,32 @@ const unsigned char __BFFFOtable[256] = {
     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
 };
 #endif
+
+/*PAGE
+ *
+ *  The following code context switches the software FPU emulation
+ *  code provided with GCC.
+ */
+
+#if (CPU_SOFTWARE_FP == TRUE)
+extern Context_Control_fp _fpCCR;
+
+void CPU_Context_save_fp (void **fp_context_ptr)
+{
+  Context_Control_fp *fp;
+
+  fp = (Context_Control_fp *) *fp_context_ptr;
+
+  *fp = _fpCCR;
+}
+
+void CPU_Context_restore_fp (void **fp_context_ptr)
+{
+  Context_Control_fp *fp;
+
+  fp = (Context_Control_fp *) *fp_context_ptr;
+
+  _fpCCR = *fp;
+}
+#endif
+

cpukit/score/src/thread.c

@@ -212,7 +212,7 @@ void _Thread_Start_multitasking( void )
     */
  
 
-#if ( CPU_HARDWARE_FP == TRUE )
+#if ( CPU_HARDWARE_FP == TRUE ) || ( CPU_SOFTWARE_FP == TRUE )
    /*
     *  don't need to worry about saving BSP's floating point state
     */