Fix uninitialized new.target register in InvokeBuiltin.

src/mips64/macro-assembler-mips64.cc

Index: src/mips64/macro-assembler-mips64.cc
diff --git a/src/mips64/macro-assembler-mips64.cc b/src/mips64/macro-assembler-mips64.cc
index 01031d49607c09c80683471b4974691a64a4892a..17852894e2373aa0ab2b54338ecf6f5569b9dd4f 100644
--- a/src/mips64/macro-assembler-mips64.cc
+++ b/src/mips64/macro-assembler-mips64.cc
@@ -4898,6 +4898,9 @@ void MacroAssembler::InvokeBuiltin(int native_context_index, InvokeFlag flag,
   // You can't call a builtin without a valid frame.
   DCHECK(flag == JUMP_FUNCTION || has_frame());
 
+  // Always initialize new target.
+  LoadRoot(a3, Heap::kUndefinedValueRootIndex);
+
   LoadNativeContextSlot(native_context_index, a1);
   ld(t9, FieldMemOperand(a1, JSFunction::kCodeEntryOffset));
   if (flag == CALL_FUNCTION) {