diff -ur mpfr-4.0.1/src/mparam_h.in mpfr-src/src/mparam_h.in
--- mpfr-4.0.1/src/mparam_h.in	Tue Jan 09 21:30:58 2018
+++ mpfr-src/src/mparam_h.in	Sat Feb 10 15:24:58 2018
@@ -32,6 +32,8 @@
    for example with gcc -dM -E -xc /dev/null
    As of gcc 4.2, you can also use: -march=native or -mtune=native */
 
+#elif 1 /* no processor specific optimization for TeX Live */
+#define MPFR_TUNE_CASE "default"
 #elif defined (__tune_pentium4__) /* Threshold for Pentium 4 */
 #define MPFR_TUNE_CASE "src/x86_64/pentium4/mparam.h"
 #include "x86_64/pentium4/mparam.h"
