--- a/js/src/jit/mips64/CodeGenerator-mips64.cpp
+++ b/js/src/jit/mips64/CodeGenerator-mips64.cpp
@@ -274,16 +274,37 @@ CodeGeneratorMIPS64::visitCompareBitwise
 
     MOZ_ASSERT(mir->jsop() == JSOP_EQ || mir->jsop() == JSOP_STRICTEQ ||
                mir->jsop() == JSOP_NE || mir->jsop() == JSOP_STRICTNE);
 
     emitBranch(lhs.valueReg(), rhs.valueReg(), cond, lir->ifTrue(), lir->ifFalse());
 }
 
 void
+CodeGeneratorMIPS64::visitAsmSelectI64(LAsmSelectI64* lir)
+{
+    MOZ_ASSERT(lir->mir()->type() == MIRType_Int64);
+
+    Register cond = ToRegister(lir->condExpr());
+    Operand falseExpr = ToOperand(lir->falseExpr());
+
+    Register out = ToRegister(lir->output());
+    MOZ_ASSERT(ToRegister(lir->trueExpr()) == out, "true expr is reused for input");
+
+    if (falseExpr.getTag() == Operand::REG) {
+        masm.as_movz(out, falseExpr.toReg(), cond);
+    } else {
+        Label done;
+        masm.ma_b(cond, cond, &done, Assembler::NonZero, ShortJump);
+        masm.loadPtr(falseExpr.toAddress(), out);
+        masm.bind(&done);
+    }
+}
+
+void
 CodeGeneratorMIPS64::setReturnDoubleRegs(LiveRegisterSet* regs)
 {
     MOZ_ASSERT(ReturnFloat32Reg.reg_ == FloatRegisters::f0);
     MOZ_ASSERT(ReturnDoubleReg.reg_ == FloatRegisters::f0);
     FloatRegister f1 = { FloatRegisters::f1, FloatRegisters::Single };
     regs->add(ReturnFloat32Reg);
     regs->add(f1);
     regs->add(ReturnDoubleReg);

--- a/js/src/jit/mips64/CodeGenerator-mips64.h
+++ b/js/src/jit/mips64/CodeGenerator-mips64.h
@@ -39,16 +39,17 @@ class CodeGeneratorMIPS64 : public CodeG
 
     void emitTableSwitchDispatch(MTableSwitch* mir, Register index, Register base);
 
   public:
     virtual void visitCompareB(LCompareB* lir);
     virtual void visitCompareBAndBranch(LCompareBAndBranch* lir);
     virtual void visitCompareBitwise(LCompareBitwise* lir);
     virtual void visitCompareBitwiseAndBranch(LCompareBitwiseAndBranch* lir);
+    virtual void visitAsmSelectI64(LAsmSelectI64* ins);
 
     // Out of line visitors.
     void visitOutOfLineBailout(OutOfLineBailout* ool);
     void visitOutOfLineTableSwitch(OutOfLineTableSwitch* ool);
   protected:
     ValueOperand ToValue(LInstruction* ins, size_t pos);
     ValueOperand ToOutValue(LInstruction* ins);
     ValueOperand ToTempValue(LInstruction* ins, size_t pos);