Why not call them UIntSize instead of FLog2 and BinSearchSize forCLog2?
That would give an indication of how to use them, and class them along
SizeOf, for finding them easily. After all, you are looking for the size
of a variable?
Wolf
On 13/06/2018 12:13, J. Gareth Moreton wrote:
I can see
I can see where you're coming from here.
If not a logarithm, what would you call
these functions that concisely and
compactly describes their behaviour and
purpose? While "bit scan reverse" is
effectively a truncated log2, with a flag
set if the input was zero, it's not a name
that jumps out
On 13/06/2018 11:07, J. Gareth Moreton wrote:
Well, I would argue that when computing log(x) of any base, as x tends
to 0 from a positive number, log(x) becomes a progressively more
negative number to the point that, yes, it's undefined, but that's
only going by the definition of limits.
Th
Well, I would argue that when computing log(x) of any base, as x tends to
0 from a positive number, log(x) becomes a progressively more negative
number to the point that, yes, it's undefined, but that's only going by the
definition of limits.
The issue here is that my proposed logarithm function
Hi
I object to one component of Gareth's proposal - to make log2(0)=0. The
problem lies not with what Gareth wants to do with it, but what other
people will use it for once it becomes available. log2(0) is undefined
(and undefinable, as it is not a computable number), the appropriate
choice
Ideally yes, but this occurs after peephole optimisations where all of the
register allocations have already been made. Doing the peephole and deep
optimisations while the registers are still in a virtual state would be
better overall, but may require a huge overhaul of the compiler that might
be
On Mon, 2018-06-11 at 21:07 +0100, J. Gareth Moreton wrote:
> Thanks David,
>
> I'm still learning some of the nuances of the Intel and AMD
> processors, but most of it is just logical analysis. Admittedly my
> main drive has been to shrink down the size of the binary, since
> Delphi and Free Pas
That would be nice, but I don't think Free
Pascal supports such a concept, at least
not yet. It would certainly be much more
flexible and allow such functions to be
distributed as part of a mathematical
package, say.
The concept of a pure function is useful
to determine for other purposes as
As pointed out in the bug report, it's not a bug. As listed in the
documentation over here:
https://www.freepascal.org/docs-html/current/ref/refsu4.html
"Every integer smaller than the ”native” size is promoted to a signed
version of the ”native” size. Integers equal to the ”native” size
keep t
Hi everyone,
Sorry to flood the mailing list again with more ideas and experiments.
I would like to propose introducing a new pair of in-built functions for
the compiler.
function FLog2(X: Cardinal): Cardinal;
function CLog2(X: Cardinal): Cardinal;
FLog2 returns the base-2 logarithm of X,
The real bug imo is that is that it even generates shl and shr instructions.
b := (a shl x) shr x should be just compile to b := a for x in 0..24 and a
being 8bit (which is what several C++ compilers do afaik)
> On 12 June 2018 at 02:07 "J. Gareth Moreton"
> wrote:
>
>
> https://bugs.freepasca
Hence why I wish to delegate this to someone more senior to decide if this
is a bug or a feature. Seems that logic has more than one path.
Mathematically, yes, shl 8 and shr 8 should cancel out completely and be a
null operation.
Gareth
On Tue 12/06/18 12:42 , Giuliano Colla giuliano.co...@fa
Il 12/06/2018 02:07, J. Gareth Moreton ha scritto:
Someone pointed out that if you perform "(x shl 8) shr 8", where x is
of type Word, the result is always x, even though logic dictates that
the upper 8 bits should be shifted out and hence the result actually
be equal to "x and $FF".
IMHO log
I will add though that Delphi apparently does the same thing, so if any
changes are made so precision is lost as expected (even though loss of
precision is usually not a desired trait), it shouldn't occur under
-mDelphi.
Personally I'm under the opinion that precision should be lost because
that
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