--- a/js/src/jit/CacheIR.h
+++ b/js/src/jit/CacheIR.h
@@ -176,16 +176,17 @@ extern const char* CacheKindNames[];
 
 #define CACHE_IR_OPS(_)                   \
     _(GuardIsObject)                      \
     _(GuardIsObjectOrNull)                \
     _(GuardIsNullOrUndefined)             \
     _(GuardIsString)                      \
     _(GuardIsSymbol)                      \
     _(GuardIsNumber)                      \
+    _(GuardIsInt32)                       \
     _(GuardIsInt32Index)                  \
     _(GuardType)                          \
     _(GuardShape)                         \
     _(GuardGroup)                         \
     _(GuardProto)                         \
     _(GuardClass)                         /* Guard an object class, per GuardClassKind */ \
     _(GuardAnyClass)                      /* Guard an arbitrary class for an object */ \
     _(GuardCompartment)                   \
@@ -530,16 +531,22 @@ class MOZ_RAII CacheIRWriter : public JS
     StringOperandId guardIsString(ValOperandId val) {
         writeOpWithOperandId(CacheOp::GuardIsString, val);
         return StringOperandId(val.id());
     }
     SymbolOperandId guardIsSymbol(ValOperandId val) {
         writeOpWithOperandId(CacheOp::GuardIsSymbol, val);
         return SymbolOperandId(val.id());
     }
+    Int32OperandId guardIsInt32(ValOperandId val) {
+        Int32OperandId res(nextOperandId_++);
+        writeOpWithOperandId(CacheOp::GuardIsInt32, val);
+        writeOperandId(res);
+        return res;
+    }
     Int32OperandId guardIsInt32Index(ValOperandId val) {
         Int32OperandId res(nextOperandId_++);
         writeOpWithOperandId(CacheOp::GuardIsInt32Index, val);
         writeOperandId(res);
         return res;
     }
     void guardIsNumber(ValOperandId val) {
         writeOpWithOperandId(CacheOp::GuardIsNumber, val);

--- a/js/src/jit/CacheIRCompiler.cpp
+++ b/js/src/jit/CacheIRCompiler.cpp
@@ -1305,16 +1305,39 @@ CacheIRCompiler::emitGuardIsSymbol()
     FailurePath* failure;
     if (!addFailurePath(&failure))
         return false;
     masm.branchTestSymbol(Assembler::NotEqual, input, failure->label());
     return true;
 }
 
 bool
+CacheIRCompiler::emitGuardIsInt32()
+{
+    ValOperandId inputId = reader.valOperandId();
+    Register output = allocator.defineRegister(masm, reader.int32OperandId());
+
+    if (allocator.knownType(inputId) == JSVAL_TYPE_INT32) {
+        Register input = allocator.useRegister(masm, Int32OperandId(inputId.id()));
+        masm.move32(input, output);
+        return true;
+    }
+    ValueOperand input = allocator.useValueRegister(masm, inputId);
+
+    FailurePath* failure;
+    if (!addFailurePath(&failure))
+        return false;
+
+    Label notInt32, done;
+    masm.branchTestInt32(Assembler::NotEqual, input, failure->label());
+    masm.unboxInt32(input, output);
+    return true;
+}
+
+bool
 CacheIRCompiler::emitGuardIsInt32Index()
 {
     ValOperandId inputId = reader.valOperandId();
     Register output = allocator.defineRegister(masm, reader.int32OperandId());
 
     if (allocator.knownType(inputId) == JSVAL_TYPE_INT32) {
         Register input = allocator.useRegister(masm, Int32OperandId(inputId.id()));
         masm.move32(input, output);

--- a/js/src/jit/CacheIRCompiler.h
+++ b/js/src/jit/CacheIRCompiler.h
@@ -18,16 +18,17 @@ namespace jit {
 // BaselineCacheIRCompiler and IonCacheIRCompiler.
 #define CACHE_IR_SHARED_OPS(_)            \
     _(GuardIsObject)                      \
     _(GuardIsNullOrUndefined)             \
     _(GuardIsObjectOrNull)                \
     _(GuardIsString)                      \
     _(GuardIsSymbol)                      \
     _(GuardIsNumber)                      \
+    _(GuardIsInt32)                       \
     _(GuardIsInt32Index)                  \
     _(GuardType)                          \
     _(GuardClass)                         \
     _(GuardIsNativeFunction)              \
     _(GuardIsNativeObject)                \
     _(GuardIsProxy)                       \
     _(GuardNotDOMProxy)                   \
     _(GuardSpecificInt32Immediate)        \