Implement fcvtmu x_d.  Fixes #339927.


git-svn-id: svn://svn.valgrind.org/vex/trunk@2982 8f6e269a-dfd6-0310-a8e1-e2731360e62c
diff --git a/priv/guest_arm64_toIR.c b/priv/guest_arm64_toIR.c
index 0377139..23aea80 100644
--- a/priv/guest_arm64_toIR.c
+++ b/priv/guest_arm64_toIR.c
@@ -12241,6 +12241,7 @@
           || (iop == Iop_F64toI64S && irrm == Irrm_PosINF) /* FCVTPS Xd,Dn */
           /* F64toI64U */
           || (iop == Iop_F64toI64U && irrm == Irrm_ZERO)   /* FCVTZU Xd,Dn */
+          || (iop == Iop_F64toI64U && irrm == Irrm_NegINF) /* FCVTMU Xd,Dn */
           || (iop == Iop_F64toI64U && irrm == Irrm_PosINF) /* FCVTPU Xd,Dn */
          ) {
         /* validated */