fdlibm: reduce accuracy slightly in favor of performance.

src/rempio2.cc

Index: src/rempio2.cc
diff --git a/src/rempio2.cc b/src/rempio2.cc
index 9d45bf364e5ef09197e44b6e3ff61772c7dd9390..dbbd8f0b00d6dc7ad7d9c5a7c8483bbc017249f0 100644
--- a/src/rempio2.cc
+++ b/src/rempio2.cc
@@ -178,10 +178,7 @@ int __kernel_rem_pio2(double* x, double* y, int e0, int nx) {
 
   fw = 0.0;
   for (int i = jz; i >= 0; i--) fw += fq[i];
-  y[0] = (ih == 0) ? fw : -fw;
-  fw = fq[0] - fw;
-  for (int i = 1; i <= jz; i++) fw += fq[i];
-  y[1] = (ih == 0) ? fw : -fw;
+  *y = (ih == 0) ? fw : -fw;
   return n & 7;
 }
 
@@ -208,8 +205,7 @@ int rempio2(double x, double* y) {
   while (tx[nx - 1] == zero) nx--;
   int n = __kernel_rem_pio2(tx, y, e0, nx);
   if (hx < 0) {
-    y[0] = -y[0];
-    y[1] = -y[1];
+    *y = -*y;
     return -n;
   }
   return n;