diff --git a/js/src/jit/x86/CodeGenerator-x86.cpp b/js/src/jit/x86/CodeGenerator-x86.cpp
index e49ac5e6af9e..9b182ef1ba3e 100644
--- a/js/src/jit/x86/CodeGenerator-x86.cpp
+++ b/js/src/jit/x86/CodeGenerator-x86.cpp
@@ -1608,3 +1608,14 @@ CodeGeneratorX86::visitInt64ToFloatingPoint(LInt64ToFloatingPoint* lir)
     if (outputType == MIRType::Float32)
         masm.convertDoubleToFloat32(output, output);
 }
+
+void
+CodeGeneratorX86::visitTestI64AndBranch(LTestI64AndBranch* lir)
+{
+    Register64 input = ToRegister64(lir->getInt64Operand(0));
+
+    masm.testl(input.high, input.high);
+    jumpToBlock(lir->ifTrue(), Assembler::NonZero);
+    masm.testl(input.low, input.low);
+    emitBranch(Assembler::NonZero, lir->ifTrue(), lir->ifFalse());
+}
diff --git a/js/src/jit/x86/CodeGenerator-x86.h b/js/src/jit/x86/CodeGenerator-x86.h
index e996f439b07e..4abe6ecc1201 100644
--- a/js/src/jit/x86/CodeGenerator-x86.h
+++ b/js/src/jit/x86/CodeGenerator-x86.h
@@ -89,6 +89,7 @@ class CodeGeneratorX86 : public CodeGeneratorX86Shared
     void visitNotI64(LNotI64* lir);
     void visitWasmTruncateToInt64(LWasmTruncateToInt64* lir);
     void visitInt64ToFloatingPoint(LInt64ToFloatingPoint* lir);
+    void visitTestI64AndBranch(LTestI64AndBranch* lir);
 
   private:
     void asmJSAtomicComputeAddress(Register addrTemp, Register ptrReg,