const_double garbage

[Richard Henderson <rth at cygnus dot com>]

Seems we are none too clean about our handling of real-valued 
constants.  I noticed this when trying to figure out why to 
builds of 104.hydra had distressingly different constants as
early as .rtl.  Of course the answer is that the second word
on a real-valued const_double is, on an alpha, unused.  And
so was never being initialized.

While the real.h and varasm.c changes are straightforward, I
also seek opinion on the print-rtl.c change.  It makes things
easier imho to figure out what's what.


r~


	* print-rtl.c (print_rtx): Display the real-value equivalent of
	a const_double when easy.

	* real.h (REAL_VALUE_TO_TARGET_SINGLE): Use a union to pun types.
	Zero memory first for predictability.
	(REAL_VALUE_TO_TARGET_DOUBLE): Likewise.
	* varasm.c (immed_real_const_1): Notice width of H_W_I == double.
	
Index: print-rtl.c
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/print-rtl.c,v
retrieving revision 1.9
diff -c -p -d -r1.9 print-rtl.c
*** print-rtl.c	1998/06/29 21:40:02	1.9
--- print-rtl.c	1998/07/04 00:22:49
*************** Boston, MA 02111-1307, USA.  */
*** 23,28 ****
--- 23,29 ----
  #include "system.h"
  #include "rtl.h"
  #include "bitmap.h"
+ #include "real.h"
  
  
  /* How to print out a register name.
*************** print_rtx (in_rtx)
*** 267,272 ****
--- 268,282 ----
  		 format_ptr[-1]);
  	abort ();
        }
+ 
+ #if HOST_FLOAT_FORMAT == TARGET_FLOAT_FORMAT
+   if (GET_CODE (in_rtx) == CONST_DOUBLE && FLOAT_MODE_P (GET_MODE (in_rtx)))
+     {
+       double val;
+       REAL_VALUE_FROM_CONST_DOUBLE (val, in_rtx);
+       fprintf (outfile, " [%.16g]", val);
+     }
+ #endif
  
    fprintf (outfile, ")");
    sawclose = 1;
Index: real.h
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/real.h,v
retrieving revision 1.7
diff -c -p -d -r1.7 real.h
*** real.h	1998/05/05 23:17:21	1.7
--- real.h	1998/07/04 00:22:49
*************** typedef struct {
*** 264,273 ****
     value in host format and then to a single type `long' value which
     is the bitwise equivalent of the `float' value.  */
  #ifndef REAL_VALUE_TO_TARGET_SINGLE
! #define REAL_VALUE_TO_TARGET_SINGLE(IN, OUT)				\
! do { float f = (float) (IN);						\
!      (OUT) = *(long *) &f;						\
!    } while (0)
  #endif
  
  /* Convert a type `double' value in host format to a pair of type `long'
--- 264,281 ----
     value in host format and then to a single type `long' value which
     is the bitwise equivalent of the `float' value.  */
  #ifndef REAL_VALUE_TO_TARGET_SINGLE
! #define REAL_VALUE_TO_TARGET_SINGLE(IN, OUT)		\
! do {							\
!   union {						\
!     float f;						\
!     HOST_WIDE_INT l;					\
!   } u;							\
!   if (sizeof(HOST_WIDE_INT) < sizeof(float))		\
!     abort();						\
!   u.l = 0;						\
!   u.f = (IN);						\
!   (OUT) = u.l;						\
! } while (0)
  #endif
  
  /* Convert a type `double' value in host format to a pair of type `long'
*************** do { float f = (float) (IN);						\
*** 275,292 ****
     proper word order for the target.  */
  #ifndef REAL_VALUE_TO_TARGET_DOUBLE
  #define REAL_VALUE_TO_TARGET_DOUBLE(IN, OUT)				\
! do { REAL_VALUE_TYPE in = (IN);  /* Make sure it's not in a register.  */\
!      if (HOST_FLOAT_WORDS_BIG_ENDIAN == FLOAT_WORDS_BIG_ENDIAN)		\
!        {								\
! 	 (OUT)[0] = ((long *) &in)[0];					\
! 	 (OUT)[1] = ((long *) &in)[1];					\
!        }								\
!      else								\
!        {								\
! 	 (OUT)[1] = ((long *) &in)[0];					\
! 	 (OUT)[0] = ((long *) &in)[1];					\
!        }								\
!    } while (0)
  #endif
  #endif /* HOST_FLOAT_FORMAT == TARGET_FLOAT_FORMAT */
  
--- 283,302 ----
     proper word order for the target.  */
  #ifndef REAL_VALUE_TO_TARGET_DOUBLE
  #define REAL_VALUE_TO_TARGET_DOUBLE(IN, OUT)				\
! do {									\
!   union {								\
!     REAL_VALUE_TYPE f;							\
!     HOST_WIDE_INT l[2];							\
!   } u;									\
!   if (sizeof(HOST_WIDE_INT) * 2 < sizeof(REAL_VALUE_TYPE))		\
!     abort();								\
!   u.l[0] = u.l[1] = 0;							\
!   u.f = (IN);								\
!   if (HOST_FLOAT_WORDS_BIG_ENDIAN == FLOAT_WORDS_BIG_ENDIAN)		\
!     (OUT)[0] = u.l[0], (OUT)[1] = u.l[1];				\
!   else									\
!     (OUT)[1] = u.l[0], (OUT)[0] = u.l[1];				\
! } while (0)
  #endif
  #endif /* HOST_FLOAT_FORMAT == TARGET_FLOAT_FORMAT */
  
Index: varasm.c
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/varasm.c,v
retrieving revision 1.36
diff -c -p -d -r1.36 varasm.c
*** varasm.c	1998/06/25 15:14:30	1.36
--- varasm.c	1998/07/04 00:22:49
*************** immed_real_const_1 (d, mode)
*** 2070,2075 ****
--- 2070,2077 ----
    else if (! REAL_VALUE_ISNAN (d) && REAL_VALUES_EQUAL (dconst1, d))
      return CONST1_RTX (mode);
  
+   if (sizeof u == sizeof (HOST_WIDE_INT))
+     return immed_double_const (u.i[0], 0, mode);
    if (sizeof u == 2 * sizeof (HOST_WIDE_INT))
      return immed_double_const (u.i[0], u.i[1], mode);