> "KF" == Ken Fox <[EMAIL PROTECTED]> writes:
> Jason Gloudon wrote:
>> http://www.ddj.com/ftp/2001/2001_07/aa0701.txt
>> I believe the LOOKUP method was the fastest for me on SPARC, if I
>> recall
>> correctly.
> Did they really spend 64K to create a lookup table just to find
Jason Gloudon wrote:
> http://www.ddj.com/ftp/2001/2001_07/aa0701.txt
>
> I believe the LOOKUP method was the fastest for me on SPARC, if I recall
> correctly.
Did they really spend 64K to create a lookup table just to find
the most significant bit? Calculating log2 for a power of two is
simpler
On Sat, Aug 03, 2002 at 12:07:30PM -0400, Ken Fox wrote:
> Nicholas Clark wrote:
> >It seems that foo & (foo - 1) is zero only for a power of 2 (or foo == 0)
> >but is there a fast way once you know that foo is a power of 2, to find out
> >log2 foo?
The ARM doesn't have a find first set bit inst
On Sat, Aug 03, 2002 at 11:35:08AM +0100, Nicholas Clark wrote:
> I presume in the general case I'd have to know whether to call
> Parrot_jit_normal_op() or Parrot_jit_cpcf_op(), so could there be a subroutine
> in jit.c that I could call to make the correct decision for me?
Here is a patch for
Nicholas Clark wrote:
> It seems that foo & (foo - 1) is zero only for a power of 2 (or foo == 0)
> but is there a fast way once you know that foo is a power of 2, to find out
> log2 foo?
You're right about (foo & (foo -1)).
gcc uses a repeated test and shift. That's works very nicely if foo
is
On Fri, Aug 02, 2002 at 03:59:28PM -0400, Richard Prescott wrote:
> IMHO, C version shall exist anyway, for speed comparaison first (it is
> always surprising how good compilers can be in some situations), then you
> could find tricks that are faster on some processors (let's say AMD) and
> not on
On Thu, 1 Aug 2002, Dan Sugalski wrote:
> At 9:42 PM +0100 8/1/02, Nicholas Clark wrote:
> >Am I allowed to write ancillary functions I want the JIT to call in
> >assembler? I presume that the JIT needs to go fast, and I suspect that there
> >are some bits that are easier to write in assembler (e
At 9:42 PM +0100 8/1/02, Nicholas Clark wrote:
>Am I allowed to write ancillary functions I want the JIT to call in
>assembler? I presume that the JIT needs to go fast, and I suspect that there
>are some bits that are easier to write in assembler (eg rotates for figuring
>out constants) than in C,
Am I allowed to write ancillary functions I want the JIT to call in
assembler? I presume that the JIT needs to go fast, and I suspect that there
are some bits that are easier to write in assembler (eg rotates for figuring
out constants) than in C, for the same amount of eventual speed.
I guess it
