Martin Sebor wrote:
>
>[EMAIL PROTECTED] wrote:
>> Author: vitek
>> Date: Wed Jun 4 14:48:36 2008
>> New Revision: 663377
>>
>[...]
>> Modified: stdcxx/branches/4.2.x/src/valarray.cpp
>> URL:
>http://svn.apache.org/viewvc/stdcxx/branches/4.2.x/src/valarray
>.cpp?rev=663377&r1=663376&r2=663377&view=diff
>>
>===============================================================
>===============
>> --- stdcxx/branches/4.2.x/src/valarray.cpp (original)
>> +++ stdcxx/branches/4.2.x/src/valarray.cpp Wed Jun 4 14:48:36 2008
>> @@ -41,8 +41,12 @@
>> {
>> _RWSTD_SIZE_T __n = _C_length.size ();
>>
>> - while (__n && _C_r_length [__n - 1] == _C_length [__n - 1] - 1)
>> - --__n;
>> + for (/**/; __n; --__n)
>> + {
>
>The brace should be on the line above :)
>
Blarg!
>> + if ( _C_length [__n - 1]
>> + && _C_r_length [__n - 1] != _C_length [__n - 1] - 1)
>
>Also, I wonder if it might help generate more optimal code to write
>the loop like so:
>
> while (__n) {
> --__n;
>
> if (_C_length [n] && _C_r_length [n] != _C_length [n] - 1)
> break;
> }
>
It is possible it would help generate better code, but this code changes
the behavior of the loop. We now decrement __n before checking the
condition; when we break __n will be off-by-one. Obviously we can deal
with that by incrementing __n before the break.
I'll take a quick look at some disassembly and decide if it is worth
making the change or not.
>The duplicate check for (0 == n) below could probably be hoisted
>into the loop for even more optimal code, something like this:
>
> for ( ; ; ) {
> if (0 == n) {
> _C_reset = true;
> break;
> }
>
> --n;
>
> if (_C_length [n] && _C_r_length [n] != _C_length [n] - 1)
> break;
> }
>
>> + break;
>> + }
>>
>> if (0 == __n) {
>> _C_reset = true;
>>
