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Code Issues 4 Releases Wiki Activity

[base] Avoid unnecessary long division. 

This applies to `FT_MulDiv' but not to `FT_DivFix', where overflows or
lack thereof are predicted accurately.

* src/base/ftcalc.c (ft_div64by32): Improve readability.
(FT_MulDiv, FT_MulDiv_No_Round) [!FT_LONG64]: Use straight division
when multiplication stayed within 32 bits.
This commit is contained in:
Alexei Podtelezhnikov 2014-09-25 22:54:38 -04:00
parent 5b68e4fb60
commit 7f49111f81
2 changed files with 20 additions and 5 deletions
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11
ChangeLog
View File

@ -1,3 +1,14 @@
2014-09-25 Alexei Podtelezhnikov <apodtele@gmail.com>
[base] Avoid unnecessary long division.
This applies to `FT_MulDiv' but not to `FT_DivFix', where overflows or
lack thereof are predicted accurately.
* src/base/ftcalc.c (ft_div64by32): Improve readability.
(FT_MulDiv, FT_MulDiv_No_Round) [!FT_LONG64]: Use straight division
when multiplication stayed within 32 bits.
2014-09-24 Werner Lemberg <wl@gnu.org>
[autofit] Minor clean-ups.

14
src/base/ftcalc.c
View File

@ -303,16 +303,14 @@
i = 32;
do
{
r <<= 1;
q <<= 1;
r |= lo >> 31;
r = ( r << 1 ) | ( lo >> 31 ); lo <<= 1; /* left 64-bit shift */
if ( r >= y )
{
r -= y;
q |= 1;
}
lo <<= 1;
} while ( --i );
return q;
@ -416,7 +414,10 @@
temp2.hi = 0;
temp2.lo = (FT_UInt32)(c >> 1);
FT_Add64( &temp, &temp2, &temp );
a = ft_div64by32( temp.hi, temp.lo, (FT_Int32)c );
/* last attempt to ditch long division */
a = temp.hi == 0 ? temp.lo / c
: ft_div64by32( temp.hi, temp.lo, (FT_Int32)c );
}
return ( s < 0 ? -a : a );
@ -450,7 +451,10 @@
ft_multo64( (FT_Int32)a, (FT_Int32)b, &temp );
a = ft_div64by32( temp.hi, temp.lo, (FT_Int32)c );
/* last attempt to ditch long division */
a = temp.hi == 0 ? temp.lo / c
: ft_div64by32( temp.hi, temp.lo, (FT_Int32)c );
}
return ( s < 0 ? -a : a );