On 26/02/2010 19:24, Ian Lance Taylor wrote:
Paolo Carlini paolo.carl...@oracle writes:
I'm trying to simplify somewhat code in the library hashing floating
point numbers, and I would find very useful a simple recipe giving the
total number of bits actually used by a long double: the basic
Hi,
I'm trying to simplify somewhat code in the library hashing floating
point numbers, and I would find very useful a simple recipe giving the
total number of bits actually used by a long double: the basic issue is
that for formats like the 80-bit Intel, I can't just rely on sizeof,
because the
Paolo Carlini paolo.carl...@oracle.com writes:
At the moment I'm trying to cook up something fixing that count with
LDBL_MANT_DIG, but maybe there is something simpler, maybe using
preprocessor builtins?!?
What's wrong with LDBL_MANT_DIG?
Andreas.
--
Andreas Schwab, sch...@linux-m68k.org
On 02/26/2010 01:03 PM, Andreas Schwab wrote:
Paolo Carlini paolo.carl...@oracle.com writes:
At the moment I'm trying to cook up something fixing that count with
LDBL_MANT_DIG, but maybe there is something simpler, maybe using
preprocessor builtins?!?
What's wrong with LDBL_MANT_DIG?
Paolo Carlini wrote:
On 02/26/2010 01:03 PM, Andreas Schwab wrote:
Paolo Carlini paolo.carl...@oracle.com writes:
At the moment I'm trying to cook up something fixing that count with
LDBL_MANT_DIG, but maybe there is something simpler, maybe using
preprocessor builtins?!?
Ed Smith-Rowland wrote:
Paolo Carlini wrote:
On 02/26/2010 01:03 PM, Andreas Schwab wrote:
Paolo Carlini paolo.carl...@oracle.com writes:
At the moment I'm trying to cook up something fixing that count with
LDBL_MANT_DIG, but maybe there is something simpler, maybe using
preprocessor
Hi,
Huh. I would have *sworn* that sizeof(long double) was 10 not 16
even though we know it was 80 bits.
normally, it's either 12, for 32-bit machines, or 16, for 64-bit
machines. In any case, there are padding bytes, which we don't want to hash.
How about (in the language of
On 2/26/2010 5:44 AM, Ed Smith-Rowland wrote:
Huh. I would have *sworn* that sizeof(long double) was 10 not 16 even
though we know it was 80 bits.
As you indicated before, sizeof gives the amount of memory displaced by
the object, including padding. In my experience with gcc, sizeof(long
On 02/26/2010 03:47 PM, Tim Prince wrote:
It seems the topic would have been more appropriate for gcc-help, if
related to gcc, or maybe comp.lang.c, if a question about
implementation in accordance with standard C.
It's neither. I was asking for the advice of the compiler people while
Paolo Carlini paolo.carl...@oracle.com writes:
Thanks. Currently I'm thinking of doing something very simple, like:
const size_t __size = __LDBL_MANT_DIG__ == 64 ? 10 : sizeof(__val);
seems conservative and I think it covers all the cases we really
support.
What is __size supposed to
On 02/26/2010 03:56 PM, Andreas Schwab wrote:
Paolo Carlini paolo.carl...@oracle.com writes:
Thanks. Currently I'm thinking of doing something very simple, like:
const size_t __size = __LDBL_MANT_DIG__ == 64 ? 10 : sizeof(__val);
seems conservative and I think it covers all the
On 02/26/2010 03:57 PM, Paolo Carlini wrote:
On 02/26/2010 03:56 PM, Andreas Schwab wrote:
Paolo Carlini paolo.carl...@oracle.com writes:
Thanks. Currently I'm thinking of doing something very simple, like:
const size_t __size = __LDBL_MANT_DIG__ == 64 ? 10 : sizeof(__val);
Paolo Carlini paolo.carl...@oracle.com writes:
On 02/26/2010 03:56 PM, Andreas Schwab wrote:
Paolo Carlini paolo.carl...@oracle.com writes:
Thanks. Currently I'm thinking of doing something very simple, like:
const size_t __size = __LDBL_MANT_DIG__ == 64 ? 10 : sizeof(__val);
Paolo Carlini paolo.carl...@oracle.com writes:
Andreas, more seriously, if you mean that __CHAR_BIT__ can be != 8, I
Don't be silly.
Andreas.
--
Andreas Schwab, sch...@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
And now for something completely
On 02/26/2010 04:41 PM, Andreas Schwab wrote:
Of what? What is the 10 magic number supposed to represent?
A size_t. Thus the number of consecutive chars occupied by the long double.
By the way, in the meanwhile I grepped config for BITS_PER_UNIT and
*finally* there are no 16 or 32 anymore.
Paolo Carlini paolo.carl...@oracle.com writes:
On 02/26/2010 04:41 PM, Andreas Schwab wrote:
Of what? What is the 10 magic number supposed to represent?
A size_t. Thus the number of consecutive chars occupied by the long double.
How does that handle padding?
Andreas.
--
Andreas
On 02/26/2010 04:51 PM, Andreas Schwab wrote:
How does that handle padding?
Andreas, I can spend the whole afternoon discussing with you one word at
a time in a kind of Socratic question and answer exchange.
You mean the padding can be *in the middle*? I didn't consider that,
seems quite
Paolo Carlini paolo.carl...@oracle.com writes:
You mean the padding can be *in the middle*? I didn't consider that,
seems quite crazy to me.
How is that crazy in any way?
If you are sure, please say it, let's skip
those 2 or 6 bytes, and be done with it. I have the patch otherwise ready.
Ok, patch canceled.
Paolo.
On 02/26/2010 05:03 PM, Andreas Schwab wrote:
If you don't care about internal padding why do you care about padding
By the way, this doesn't make any sense to me: I don't see what the CPU
gains from having padding between mantissa and exponent, or different
bytes of the mantissa. If you really
On 26/02/2010 15:45, Paolo Carlini wrote:
On 02/26/2010 04:41 PM, Andreas Schwab wrote:
Of what? What is the 10 magic number supposed to represent?
A size_t. Thus the number of consecutive chars occupied by the long double.
By the way, in the meanwhile I grepped config for BITS_PER_UNIT
Paolo Carlini paolo.carl...@oracle.com writes:
By the way, this doesn't make any sense to me: I don't see what the CPU
gains from having padding between mantissa and exponent, or different
bytes of the mantissa.
It's a fact of life. I didn't design the motorola floating point format.
If
On 02/26/2010 05:36 PM, Andreas Schwab wrote:
See libiberty/floatformat.c.
Ok, thanks. Actually, it looks like there is *no* padding in the middle
for the Intel x87 format I truly care about:
const struct floatformat floatformat_i387_ext =
{
floatformat_little, 80, 0, 1, 15, 0x3fff,
Paolo Carlini paolo.carl...@oracle.com writes:
But really we don't want to deal with all those special cases for other
formats, for now at least. Too bad.
But LDBL_MANT_DIG == 64 is ambigous for identifying the floating point
format.
Andreas.
--
Andreas Schwab, sch...@linux-m68k.org
GPG Key
On Fri, Feb 26, 2010 at 06:09:37PM +0100, Paolo Carlini wrote:
On 02/26/2010 05:36 PM, Andreas Schwab wrote:
See libiberty/floatformat.c.
Ok, thanks. Actually, it looks like there is *no* padding in the middle
for the Intel x87 format I truly care about:
const struct floatformat
On 02/26/2010 07:05 PM, Andreas Schwab wrote:
But really we don't want to deal with all those special cases for other
formats, for now at least. Too bad.
But LDBL_MANT_DIG == 64 is ambigous for identifying the floating point
format.
Sure, sure. I meant, there are too many formats and
On 02/26/2010 07:07 PM, Daniel Jacobowitz wrote:
Despite all that exchange, I don't think you ever answered Andreas's
question - at least not in a way that I could understand. A size of
what? The size of the *type* on x86 is 16; the size of the *data
bits* is 10. But what cares about the
Paolo Carlini paolo.carl...@oracle.com writes:
I'm tired. Anyway, I meant of course the size of the *data bits*, using
your terminology. For *some* formats, like x87, where there are no
holes, no padding bits in the middle of the representation, that is all
I would need. In the meanwhile,
Paolo Carlini paolo.carl...@oracle.com writes:
I'm trying to simplify somewhat code in the library hashing floating
point numbers, and I would find very useful a simple recipe giving the
total number of bits actually used by a long double: the basic issue is
that for formats like the 80-bit
Feb 26, 2010 01:43:15 PM, sch...@linux-m68k.org wrote:
Paolo Carlini writes:
I'm tired. Anyway, I meant of course the size of the *data bits*, using
your terminology. For *some* formats, like x87, where there are no
holes, no padding bits in the middle of the representation, that is all
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