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Fix a regression introduced in r226371: When the high part of x*y

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exactly cancels with z, return the low part of x*y instead of
discarding it.
This commit is contained in:
David Schultz 2011-10-21 06:30:43 +00:00
parent bc23acdc32
commit 0c7e4d5fc1
2 changed files with 6 additions and 6 deletions
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6
lib/msun/src/s_fma.c
View File

@ -250,6 +250,8 @@ fma(double x, double y, double z)
xy = dd_mul(xs, ys);
r = dd_add(xy.hi, zs);
spread = ex + ey;
if (r.hi == 0.0) {
/*
* When the addends cancel to 0, ensure that the result has
@ -257,11 +259,9 @@ fma(double x, double y, double z)
*/
fesetround(oround);
volatile double vzs = zs; /* XXX gcc CSE bug workaround */
return (xy.hi + vzs);
return (xy.hi + vzs + ldexp(xy.lo, spread));
}
spread = ex + ey;
if (oround != FE_TONEAREST) {
/*
* There is no need to worry about double rounding in directed

6
lib/msun/src/s_fmal.c
View File

@ -238,6 +238,8 @@ fmal(long double x, long double y, long double z)
xy = dd_mul(xs, ys);
r = dd_add(xy.hi, zs);
spread = ex + ey;
if (r.hi == 0.0) {
/*
* When the addends cancel to 0, ensure that the result has
@ -245,11 +247,9 @@ fmal(long double x, long double y, long double z)
*/
fesetround(oround);
volatile long double vzs = zs; /* XXX gcc CSE bug workaround */
return (xy.hi + vzs);
return (xy.hi + vzs + ldexpl(xy.lo, spread));
}
spread = ex + ey;
if (oround != FE_TONEAREST) {
/*
* There is no need to worry about double rounding in directed