diff -up R-3.6.2/src/main/arithmetic.c.ppc64 R-3.6.2/src/main/arithmetic.c
--- R-3.6.2/src/main/arithmetic.c.ppc64	2019-10-18 18:15:02.000000000 -0400
+++ R-3.6.2/src/main/arithmetic.c	2019-12-18 09:05:50.363220122 -0500
@@ -177,7 +177,12 @@ void attribute_hidden InitArithmetic()
 }
 
 #if HAVE_LONG_DOUBLE && (SIZEOF_LONG_DOUBLE > SIZEOF_DOUBLE)
+# ifdef __PPC64__
+ // PowerPC 64 (when gcc has -mlong-double-128) fails constant folding with LDOUBLE
+#  define q_1_eps (1 / LDBL_EPSILON)
+# else
 static LDOUBLE q_1_eps = 1 / LDBL_EPSILON;
+# endif
 #else
 static double  q_1_eps = 1 / DBL_EPSILON;
 #endif