S390: Optimize For Mul in TurboFan codegen

src/s390/assembler-s390.cc

Index: src/s390/assembler-s390.cc
diff --git a/src/s390/assembler-s390.cc b/src/s390/assembler-s390.cc
index 2ce55366d4d5ca37ede22b5d5b5bbd32907ecc45..a448947307df5c39b741017dca0ce774cccecc6b 100644
--- a/src/s390/assembler-s390.cc
+++ b/src/s390/assembler-s390.cc
@@ -2098,9 +2098,15 @@ void Assembler::slgrk(Register r1, Register r2, Register r3) {
 // ----------------------------
 // Multiply Register-Storage (64<32)
 void Assembler::m(Register r1, const MemOperand& opnd) {
+  DCHECK(r1.code() % 2 == 0);
   rx_form(M, r1, opnd.rx(), opnd.rb(), opnd.offset());
 }
 
+void Assembler::mfy(Register r1, const MemOperand& opnd) {
+  DCHECK(r1.code() % 2 == 0);
+  rxy_form(MFY, r1, opnd.rx(), opnd.rb(), opnd.offset());
+}
+
 // Multiply Register (64<32)
 void Assembler::mr_z(Register r1, Register r2) {
   DCHECK(r1.code() % 2 == 0);