Re: Computer architects leaving Intel...

mitchalsup@aol.com (MitchAlsup1) writes:

And just for fun::
>
On Fri, 6 Sep 2024 13:26:42 +0000, Anton Ertl wrote:

Here we have the three variants:
>
#include <limits.h>
>
extern long foo1(long);
extern long foo2(long);
>
long bar(long a, long b)
{
  long c;
  if (__builtin_sub_overflow(b,1,&c))
    return foo1(a);
  else
    return foo2(a);
}
>
long bar2(long a, long b)
{
  if (b < b-1)
    return foo1(a);
  else
    return foo2(a);
}
>
long bar3(long a, long b)
{
  if (b == LONG_MIN)
    return foo1(a);
  else
    return foo2(a);
}

>
My 66000:
   add    r3,R1,#-1   add  r3,r1,#-1         bepm  r1,.L4
   bge    R3,.L4      bge  r3,.L4
   8-bytes            8-bytes                4-bytes
>
I have a direct test for POSMAX in ISA that does not use a constant.

How does bge work in the first and second column?  My impression was
that you are using an 88k-style flags-in-GPR architecture.

Concerning the last column, the gcc developer who added the
transformation of bar2() into bar3() apparently had My66000 in mind.

- anton
--
'Anyone trying for "industrial quality" ISA should avoid undefined behavior.'
  Mitch Alsup, <c17fcd89-f024-40e7-a594-88a85ac10d20o@googlegroups.com>