🚀 go-pugleaf

The applies to gcc version 1.35 in the target independent portions of the code.

The following code fragment in the function "copy_rtx_if_shared()" in the file
"emit-rtl.c" is not very robustly portable:

 bcopy (x, copy, sizeof (int) * (GET_RTX_LENGTH (code) + 1));

Notice how the length in bytes of an rtx is calculated.  This
code depends to heavily (and subtly) on the fact that an rtx_def
is exactly 12 bytes (or 3x32 bit words) long.  A lot of care in
the definition of rtx_def has attempted to assure this, but the
C compiler available to me doesn't treat bitfields and enums so 
well, so things don't work out so nicely.  

The function "rtx_alloc()" in the file "rtl.c" accomplishes the
same result in a much more portable way:

/* Allocate an rtx of code CODE.  The CODE is stored in the rtx;
   all the rest is initialized to zero.  */

rtx
rtx_alloc (code)
  RTX_CODE code;
{
  rtx rt;
  register int nelts = GET_RTX_LENGTH (code);
  register int length = sizeof (struct rtx_def)
    + (nelts - 1) * sizeof (rtunion);

  rt = (rtx) obstack_alloc (rtl_obstack, length);

  * (int *) rt = 0;
  PUT_CODE (rt, code);

  return rt;
}

I propose that the code fragment in emit-rtl.c use the
same code as rtx_alloc.  Better yet, the following function
could be defined and used in both cases:

int
rtx_node_length_in_bytes(code)
RTX_CODE code;
{	
  int nelts = GET_RTX_LENGTH (code);
  int length = sizeof (struct rtx_def)
      + (nelts - 1) * sizeof (rtunion);

   return ( length );
}

I'd appreciate any feedback on this proposed small change.
I would like to get a feel for what kind of code
improvements are accepted by GNU for gcc.

--
Peter Ham			PO Box 3430	(415) 324-4782
MS Computer Science Student	Stanford, CA	ham@polya.stanford.edu
Stanford University 		94309