From 0c7e4d5fc1fc5b7ecbe565d6324cb6253bec5ebe Mon Sep 17 00:00:00 2001 From: David Schultz Date: Fri, 21 Oct 2011 06:30:43 +0000 Subject: [PATCH] Fix a regression introduced in r226371: When the high part of x*y exactly cancels with z, return the low part of x*y instead of discarding it. --- lib/msun/src/s_fma.c | 6 +++--- lib/msun/src/s_fmal.c | 6 +++--- 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/lib/msun/src/s_fma.c b/lib/msun/src/s_fma.c index 9cb0ddc8ac53..dfbd13c46815 100644 --- a/lib/msun/src/s_fma.c +++ b/lib/msun/src/s_fma.c @@ -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 diff --git a/lib/msun/src/s_fmal.c b/lib/msun/src/s_fmal.c index 59fa6cd4ffef..c2a691350999 100644 --- a/lib/msun/src/s_fmal.c +++ b/lib/msun/src/s_fmal.c @@ -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