Fix compilation error on gcc 4.8.5 on s390x

src/base/ieee754.cc

Index: src/base/ieee754.cc
diff --git a/src/base/ieee754.cc b/src/base/ieee754.cc
index 94bc7d350fe8cf8dffedd23b8fac70065b497913..d0faeeea0063ed701bb8853a35157be4203d066a 100644
--- a/src/base/ieee754.cc
+++ b/src/base/ieee754.cc
@@ -609,7 +609,7 @@ recompute:
     j = 0;
     for (i = jz - 1; i >= jk; i--) j |= iq[i];
     if (j == 0) { /* need recomputation */
-      for (k = 1; iq[jk - k] == 0; k++) {
+      for (k = 1; jk >= k && iq[jk - k] == 0; k++) {
         /* k = no. of terms needed */
       }