1 files changed, 4 insertions, 14 deletions
diff --git a/Objects/floatobject.c b/Objects/floatobject.c
index 6a2af743af..865c960b88 100644
--- a/Objects/floatobject.c
+++ b/Objects/floatobject.c
@@ -600,20 +600,10 @@ float_rem(PyObject *v, PyObject *w)
 #endif
     PyFPE_START_PROTECT("modulo", return 0)
     mod = fmod(vx, wx);
-    if (mod) {
-        /* ensure the remainder has the same sign as the denominator */
-        if ((wx < 0) != (mod < 0)) {
-            mod += wx;
-        }
-    }
-    else {
-        /* the remainder is zero, and in the presence of signed zeroes
-           fmod returns different results across platforms; ensure
-           it has the same sign as the denominator; we'd like to do
-           "mod = wx * 0.0", but that may get optimized away */
-        mod *= mod;  /* hide "mod = +0" from optimizer */
-        if (wx < 0.0)
-            mod = -mod;
+    /* note: checking mod*wx < 0 is incorrect -- underflows to
+       0 if wx < sqrt(smallest nonzero double) */
+    if (mod && ((wx < 0) != (mod < 0))) {
+        mod += wx;
     }
     PyFPE_END_PROTECT(mod)
     return PyFloat_FromDouble(mod);