--- a/js/src/jit/mips64/CodeGenerator-mips64.cpp
+++ b/js/src/jit/mips64/CodeGenerator-mips64.cpp
@@ -299,16 +299,45 @@ 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::visitWasmLoadI64(LWasmLoadI64* lir)
+{
+    const MWasmLoad* mir = lir->mir();
+
+    MOZ_ASSERT(lir->mir()->type() == MIRType::Int64);
+    MOZ_ASSERT(!mir->barrierBefore() && !mir->barrierAfter(), "atomics NYI");
+
+    uint32_t offset = mir->offset();
+    if (offset > INT32_MAX) {
+        // This is unreachable because of bounds checks.
+        masm.breakpoint();
+        return;
+    }
+
+    Register ptr = ToRegister(lir->ptr());
+
+    // Maybe add the offset.
+    if (offset) {
+        Register ptrPlusOffset = ToRegister(lir->ptrCopy());
+        masm.addPtr(Imm32(offset), ptrPlusOffset);
+        ptr = ptrPlusOffset;
+    } else {
+        MOZ_ASSERT(lir->ptrCopy()->isBogusTemp());
+    }
+
+    masm.ma_load(ToRegister(lir->output()), BaseIndex(HeapReg, ptr, TimesOne), SizeDouble);
+}
+
+void
 CodeGeneratorMIPS64::visitAsmSelectI64(LAsmSelectI64* lir)
 {
     MOZ_ASSERT(lir->mir()->type() == MIRType::Int64);
 
     Register cond = ToRegister(lir->condExpr());
     const LAllocation* falseExpr = lir->falseExpr();
 
     Register out = ToRegister(lir->output());

--- 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:
     void visitCompareB(LCompareB* lir);
     void visitCompareBAndBranch(LCompareBAndBranch* lir);
     void visitCompareBitwise(LCompareBitwise* lir);
     void visitCompareBitwiseAndBranch(LCompareBitwiseAndBranch* lir);
+    void visitWasmLoadI64(LWasmLoadI64* lir);
     void visitAsmSelectI64(LAsmSelectI64* ins);
     void visitAsmReinterpretFromI64(LAsmReinterpretFromI64* lir);
     void visitAsmReinterpretToI64(LAsmReinterpretToI64* lir);
 
     // Out of line visitors.
     void visitOutOfLineBailout(OutOfLineBailout* ool);
     void visitOutOfLineTableSwitch(OutOfLineTableSwitch* ool);
   protected: