diff --git a/js/src/assembler/assembler/MacroAssemblerX86Common.cpp b/js/src/assembler/assembler/MacroAssemblerX86Common.cpp
index 6b1a1bbcd146..b94a345ff649 100644
--- a/js/src/assembler/assembler/MacroAssemblerX86Common.cpp
+++ b/js/src/assembler/assembler/MacroAssemblerX86Common.cpp
@@ -14,5 +14,9 @@
 using namespace JSC;
 MacroAssemblerX86Common::SSECheckState MacroAssemblerX86Common::s_sseCheckState = NotCheckedSSE;
 
+#ifdef DEBUG
+bool MacroAssemblerX86Common::s_floatingPointDisabled = false;
+#endif
+
 #endif /* WTF_CPU_X86 || WTF_CPU_X86_64 */
 
diff --git a/js/src/assembler/assembler/MacroAssemblerX86Common.h b/js/src/assembler/assembler/MacroAssemblerX86Common.h
index d1c2b08c2523..30bb1ed26afc 100644
--- a/js/src/assembler/assembler/MacroAssemblerX86Common.h
+++ b/js/src/assembler/assembler/MacroAssemblerX86Common.h
@@ -1374,6 +1374,15 @@ private:
              );
 #endif
 #endif
+
+#ifdef DEBUG
+        if (s_floatingPointDisabled) {
+            // Disable SSE2.
+            s_sseCheckState = HasSSE;
+            return;
+        }
+#endif
+
         static const int SSEFeatureBit = 1 << 25;
         static const int SSE2FeatureBit = 1 << 26;
         static const int SSE3FeatureBit = 1 << 0;
@@ -1407,6 +1416,10 @@ private:
 
     static bool isSSE2Present()
     {
+#ifdef DEBUG
+        if (s_floatingPointDisabled)
+            return false;
+#endif
         return true;
     }
 
@@ -1489,6 +1502,15 @@ private:
 
         return s_sseCheckState >= HasSSE4_2;
     }
+
+#ifdef DEBUG
+    static bool s_floatingPointDisabled;
+
+  public:
+    static void SetFloatingPointDisabled() {
+        s_floatingPointDisabled = true;
+    }
+#endif
 };
 
 } // namespace JSC
diff --git a/js/src/ion/BaselineIC.cpp b/js/src/ion/BaselineIC.cpp
index 680550281d8a..77ad553d42f5 100644
--- a/js/src/ion/BaselineIC.cpp
+++ b/js/src/ion/BaselineIC.cpp
@@ -1662,6 +1662,9 @@ DoCompareFallback(JSContext *cx, BaselineFrame *frame, ICCompare_Fallback *stub,
         return true;
     }
 
+    if (!cx->runtime->jitSupportsFloatingPoint && (lhs.isNumber() || rhs.isNumber()))
+        return true;
+
     if (lhs.isNumber() && rhs.isNumber()) {
         IonSpew(IonSpew_BaselineIC, "  Generating %s(Number, Number) stub", js_CodeName[op]);
 
@@ -2070,7 +2073,7 @@ DoToBoolFallback(JSContext *cx, BaselineFrame *frame, ICToBool_Fallback *stub, H
         return true;
     }
 
-    if (arg.isDouble()) {
+    if (arg.isDouble() && cx->runtime->jitSupportsFloatingPoint) {
         IonSpew(IonSpew_BaselineIC, "  Generating ToBool(Double) stub.");
         ICToBool_Double::Compiler compiler(cx);
         ICStub *doubleStub = compiler.getStub(compiler.getStubSpace(script));
@@ -2456,6 +2459,9 @@ DoBinaryArithFallback(JSContext *cx, BaselineFrame *frame, ICBinaryArith_Fallbac
     JS_ASSERT(ret.isNumber());
 
     if (lhs.isDouble() || rhs.isDouble() || ret.isDouble()) {
+        if (!cx->runtime->jitSupportsFloatingPoint)
+            return true;
+
         switch (op) {
           case JSOP_ADD:
           case JSOP_SUB:
@@ -2912,7 +2918,10 @@ DoUnaryArithFallback(JSContext *cx, BaselineFrame *frame, ICUnaryArith_Fallback
         return true;
     }
 
-    if (val.isNumber() && res.isNumber() && op == JSOP_NEG) {
+    if (val.isNumber() && res.isNumber() &&
+        op == JSOP_NEG &&
+        cx->runtime->jitSupportsFloatingPoint)
+    {
         IonSpew(IonSpew_BaselineIC, "  Generating %s(Number => Number) stub", js_CodeName[op]);
         // Unlink int32 stubs, the double stub handles both cases and TI specializes for both.
         stub->unlinkStubsWithKind(cx, ICStub::UnaryArith_Int32);
@@ -3255,6 +3264,15 @@ static bool TryAttachNativeGetElemStub(JSContext *cx, HandleScript script,
     return true;
 }
 
+static bool
+TypedArrayRequiresFloatingPoint(JSObject *obj)
+{
+    uint32_t type = TypedArray::type(obj);
+    return (type == TypedArray::TYPE_UINT32 ||
+            type == TypedArray::TYPE_FLOAT32 ||
+            type == TypedArray::TYPE_FLOAT64);
+}
+
 static bool
 TryAttachGetElemStub(JSContext *cx, HandleScript script, ICGetElem_Fallback *stub,
                      HandleValue lhs, HandleValue rhs, HandleValue res)
@@ -3303,6 +3321,9 @@ TryAttachGetElemStub(JSContext *cx, HandleScript script, ICGetElem_Fallback *stu
     if (obj->isTypedArray() && rhs.isInt32() && res.isNumber() &&
         !TypedArrayGetElemStubExists(stub, obj))
     {
+        if (!cx->runtime->jitSupportsFloatingPoint && TypedArrayRequiresFloatingPoint(obj))
+            return true;
+
         IonSpew(IonSpew_BaselineIC, "  Generating GetElem(TypedArray[Int32]) stub");
         ICGetElem_TypedArray::Compiler compiler(cx, obj->lastProperty(), TypedArray::type(obj));
         ICStub *typedArrayStub = compiler.getStub(compiler.getStubSpace(script));
@@ -3828,6 +3849,9 @@ DoSetElemFallback(JSContext *cx, BaselineFrame *frame, ICSetElem_Fallback *stub,
     }
 
     if (obj->isTypedArray() && index.isInt32() && rhs.isNumber()) {
+        if (!cx->runtime->jitSupportsFloatingPoint && TypedArrayRequiresFloatingPoint(obj))
+            return true;
+
         uint32_t len = TypedArray::length(obj);
         int32_t idx = index.toInt32();
         bool expectOutOfBounds = (idx < 0) || (static_cast<uint32_t>(idx) >= len);
@@ -3980,9 +4004,14 @@ ICSetElem_Dense::Compiler::generateStubCode(MacroAssembler &masm)
     masm.storeValue(R0, element);
     EmitReturnFromIC(masm);
 
-    // Convert to double and jump back.
+    // Convert to double and jump back. Note that double arrays are only
+    // created by IonMonkey, so if we have no floating-point support
+    // Ion is disabled and there should be no double arrays.
     masm.bind(&convertDoubles);
-    masm.convertInt32ValueToDouble(valueAddr, R0.scratchReg(), &convertDoublesDone);
+    if (cx->runtime->jitSupportsFloatingPoint)
+        masm.convertInt32ValueToDouble(valueAddr, R0.scratchReg(), &convertDoublesDone);
+    else
+        masm.breakpoint();
     masm.jump(&convertDoublesDone);
 
     // Failure case - fail but first unstow R0 and R1
@@ -4143,9 +4172,14 @@ ICSetElemDenseAddCompiler::generateStubCode(MacroAssembler &masm)
     masm.storeValue(R0, element);
     EmitReturnFromIC(masm);
 
-    // Convert to double and jump back.
+    // Convert to double and jump back. Note that double arrays are only
+    // created by IonMonkey, so if we have no floating-point support
+    // Ion is disabled and there should be no double arrays.
     masm.bind(&convertDoubles);
-    masm.convertInt32ValueToDouble(valueAddr, R0.scratchReg(), &convertDoublesDone);
+    if (cx->runtime->jitSupportsFloatingPoint)
+        masm.convertInt32ValueToDouble(valueAddr, R0.scratchReg(), &convertDoublesDone);
+    else
+        masm.breakpoint();
     masm.jump(&convertDoublesDone);
 
     // Failure case - fail but first unstow R0 and R1
@@ -4218,10 +4252,14 @@ ICSetElem_TypedArray::Compiler::generateStubCode(MacroAssembler &masm)
         // If the value is a double, clamp to uint8 and jump back.
         // Else, jump to failure.
         masm.bind(&notInt32);
-        masm.branchTestDouble(Assembler::NotEqual, value, &failure);
-        masm.unboxDouble(value, FloatReg0);
-        masm.clampDoubleToUint8(FloatReg0, secondScratch);
-        masm.jump(&clamped);
+        if (cx->runtime->jitSupportsFloatingPoint) {
+            masm.branchTestDouble(Assembler::NotEqual, value, &failure);
+            masm.unboxDouble(value, FloatReg0);
+            masm.clampDoubleToUint8(FloatReg0, secondScratch);
+            masm.jump(&clamped);
+        } else {
+            masm.jump(&failure);
+        }
     } else {
         Label notInt32;
         masm.branchTestInt32(Assembler::NotEqual, value, &notInt32);
@@ -4236,10 +4274,14 @@ ICSetElem_TypedArray::Compiler::generateStubCode(MacroAssembler &masm)
         // Else, jump to failure.
         Label failureRestoreRegs;
         masm.bind(&notInt32);
-        masm.branchTestDouble(Assembler::NotEqual, value, &failure);
-        masm.unboxDouble(value, FloatReg0);
-        masm.branchTruncateDouble(FloatReg0, secondScratch, &failureRestoreRegs);
-        masm.jump(&isInt32);
+        if (cx->runtime->jitSupportsFloatingPoint) {
+            masm.branchTestDouble(Assembler::NotEqual, value, &failure);
+            masm.unboxDouble(value, FloatReg0);
+            masm.branchTruncateDouble(FloatReg0, secondScratch, &failureRestoreRegs);
+            masm.jump(&isInt32);
+        } else {
+            masm.jump(&failure);
+        }
 
         // Writing to secondScratch may have clobbered R0 or R1, restore them
         // first.
@@ -6511,6 +6553,18 @@ ICCall_Native::Compiler::generateStubCode(MacroAssembler &masm)
     return true;
 }
 
+static JSBool
+DoubleValueToInt32ForSwitch(Value *v)
+{
+    double d = v->toDouble();
+    int32_t truncated = int32_t(d);
+    if (d != double(truncated))
+        return false;
+
+    v->setInt32(truncated);
+    return true;
+}
+
 bool
 ICTableSwitch::Compiler::generateStubCode(MacroAssembler &masm)
 {
@@ -6537,10 +6591,27 @@ ICTableSwitch::Compiler::generateStubCode(MacroAssembler &masm)
     masm.bind(&notInt32);
 
     masm.branchTestDouble(Assembler::NotEqual, R0, &outOfRange);
-    masm.unboxDouble(R0, FloatReg0);
+    if (cx->runtime->jitSupportsFloatingPoint) {
+        masm.unboxDouble(R0, FloatReg0);
 
-    // N.B. -0 === 0, so convert -0 to a 0 int32.
-    masm.convertDoubleToInt32(FloatReg0, key, &outOfRange, /* negativeZeroCheck = */ false);
+        // N.B. -0 === 0, so convert -0 to a 0 int32.
+        masm.convertDoubleToInt32(FloatReg0, key, &outOfRange, /* negativeZeroCheck = */ false);
+    } else {
+        // Pass pointer to double value.
+        masm.pushValue(R0);
+        masm.movePtr(StackPointer, R0.scratchReg());
+
+        masm.setupUnalignedABICall(1, scratch);
+        masm.passABIArg(R0.scratchReg());
+        masm.callWithABI(JS_FUNC_TO_DATA_PTR(void *, DoubleValueToInt32ForSwitch));
+
+        // If the function returns |true|, the value has been converted to
+        // int32.
+        masm.mov(ReturnReg, scratch);
+        masm.popValue(R0);
+        masm.branchTest32(Assembler::Zero, scratch, scratch, &outOfRange);
+        masm.unboxInt32(R0, key);
+    }
     masm.jump(&isInt32);
 
     masm.bind(&outOfRange);
diff --git a/js/src/ion/BaselineJIT.h b/js/src/ion/BaselineJIT.h
index 435d72d749a6..2c9e914c5042 100644
--- a/js/src/ion/BaselineJIT.h
+++ b/js/src/ion/BaselineJIT.h
@@ -249,7 +249,8 @@ struct BaselineScript
     }
 };
 
-inline bool IsBaselineEnabled(JSContext *cx)
+inline bool
+IsBaselineEnabled(JSContext *cx)
 {
     return cx->hasOption(JSOPTION_BASELINE);
 }
diff --git a/js/src/ion/Ion.cpp b/js/src/ion/Ion.cpp
index f34c93408410..aa98642c6836 100644
--- a/js/src/ion/Ion.cpp
+++ b/js/src/ion/Ion.cpp
@@ -198,23 +198,30 @@ IonRuntime::initialize(JSContext *cx)
     if (!functionWrappers_ || !functionWrappers_->init())
         return false;
 
-    if (!bailoutTables_.reserve(FrameSizeClass::ClassLimit().classId()))
-        return false;
+    if (cx->runtime->jitSupportsFloatingPoint) {
+        // Initialize some Ion-only stubs that require floating-point support.
+        if (!bailoutTables_.reserve(FrameSizeClass::ClassLimit().classId()))
+            return false;
 
-    for (uint32_t id = 0;; id++) {
-        FrameSizeClass class_ = FrameSizeClass::FromClass(id);
-        if (class_ == FrameSizeClass::ClassLimit())
-            break;
-        bailoutTables_.infallibleAppend((IonCode *)NULL);
-        bailoutTables_[id] = generateBailoutTable(cx, id);
-        if (!bailoutTables_[id])
+        for (uint32_t id = 0;; id++) {
+            FrameSizeClass class_ = FrameSizeClass::FromClass(id);
+            if (class_ == FrameSizeClass::ClassLimit())
+                break;
+            bailoutTables_.infallibleAppend((IonCode *)NULL);
+            bailoutTables_[id] = generateBailoutTable(cx, id);
+            if (!bailoutTables_[id])
+                return false;
+        }
+
+        bailoutHandler_ = generateBailoutHandler(cx);
+        if (!bailoutHandler_)
+            return false;
+
+        invalidator_ = generateInvalidator(cx);
+        if (!invalidator_)
             return false;
     }
 
-    bailoutHandler_ = generateBailoutHandler(cx);
-    if (!bailoutHandler_)
-        return false;
-
     argumentsRectifier_ = generateArgumentsRectifier(cx, SequentialExecution, &argumentsRectifierReturnAddr_);
     if (!argumentsRectifier_)
         return false;
@@ -225,10 +232,6 @@ IonRuntime::initialize(JSContext *cx)
         return false;
 #endif
 
-    invalidator_ = generateInvalidator(cx);
-    if (!invalidator_)
-        return false;
-
     enterJIT_ = generateEnterJIT(cx, EnterJitOptimized);
     if (!enterJIT_)
         return false;
diff --git a/js/src/ion/shared/Assembler-x86-shared.h b/js/src/ion/shared/Assembler-x86-shared.h
index 1fff30bd405b..41cb8e0bc5da 100644
--- a/js/src/ion/shared/Assembler-x86-shared.h
+++ b/js/src/ion/shared/Assembler-x86-shared.h
@@ -278,9 +278,11 @@ class AssemblerX86Shared
     }
 
     void movsd(const FloatRegister &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.movsd_rr(src.code(), dest.code());
     }
     void movsd(const Operand &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         switch (src.kind()) {
           case Operand::FPREG:
             masm.movsd_rr(src.fpu(), dest.code());
@@ -296,6 +298,7 @@ class AssemblerX86Shared
         }
     }
     void movsd(const FloatRegister &src, const Operand &dest) {
+        JS_ASSERT(HasSSE2());
         switch (dest.kind()) {
           case Operand::FPREG:
             masm.movsd_rr(src.code(), dest.fpu());
@@ -311,6 +314,7 @@ class AssemblerX86Shared
         }
     }
     void movss(const Operand &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         switch (src.kind()) {
           case Operand::REG_DISP:
             masm.movss_mr(src.disp(), src.base(), dest.code());
@@ -323,6 +327,7 @@ class AssemblerX86Shared
         }
     }
     void movss(const FloatRegister &src, const Operand &dest) {
+        JS_ASSERT(HasSSE2());
         switch (dest.kind()) {
           case Operand::REG_DISP:
             masm.movss_rm(src.code(), dest.disp(), dest.base());
@@ -335,6 +340,7 @@ class AssemblerX86Shared
         }
     }
     void movdqa(const Operand &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         switch (src.kind()) {
           case Operand::REG_DISP:
             masm.movdqa_mr(src.disp(), src.base(), dest.code());
@@ -347,6 +353,7 @@ class AssemblerX86Shared
         }
     }
     void movdqa(const FloatRegister &src, const Operand &dest) {
+        JS_ASSERT(HasSSE2());
         switch (dest.kind()) {
           case Operand::REG_DISP:
             masm.movdqa_rm(src.code(), dest.disp(), dest.base());
@@ -359,9 +366,11 @@ class AssemblerX86Shared
         }
     }
     void cvtss2sd(const FloatRegister &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.cvtss2sd_rr(src.code(), dest.code());
     }
     void cvtsd2ss(const FloatRegister &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.cvtsd2ss_rr(src.code(), dest.code());
     }
     void movzbl(const Operand &src, const Register &dest) {
@@ -655,6 +664,9 @@ class AssemblerX86Shared
         masm.int3();
     }
 
+    static bool HasSSE2() {
+        return JSC::MacroAssembler::getSSEState() >= JSC::MacroAssembler::HasSSE2;
+    }
     static bool HasSSE41() {
         return JSC::MacroAssembler::getSSEState() >= JSC::MacroAssembler::HasSSE4_1;
     }
@@ -1052,12 +1064,15 @@ class AssemblerX86Shared
     }
 
     void unpcklps(const FloatRegister &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.unpcklps_rr(src.code(), dest.code());
     }
     void pinsrd(const Register &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.pinsrd_rr(src.code(), dest.code());
     }
     void pinsrd(const Operand &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         switch (src.kind()) {
           case Operand::REG:
             masm.pinsrd_rr(src.reg(), dest.code());
@@ -1070,16 +1085,20 @@ class AssemblerX86Shared
         }
     }
     void psrldq(Imm32 shift, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.psrldq_rr(dest.code(), shift.value);
     }
     void psllq(Imm32 shift, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.psllq_rr(dest.code(), shift.value);
     }
     void psrlq(Imm32 shift, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.psrlq_rr(dest.code(), shift.value);
     }
 
     void cvtsi2sd(const Operand &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         switch (src.kind()) {
           case Operand::REG:
             masm.cvtsi2sd_rr(src.reg(), dest.code());
@@ -1095,12 +1114,15 @@ class AssemblerX86Shared
         }
     }
     void cvttsd2si(const FloatRegister &src, const Register &dest) {
+        JS_ASSERT(HasSSE2());
         masm.cvttsd2si_rr(src.code(), dest.code());
     }
     void cvtsi2sd(const Register &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.cvtsi2sd_rr(src.code(), dest.code());
     }
     void movmskpd(const FloatRegister &src, const Register &dest) {
+        JS_ASSERT(HasSSE2());
         masm.movmskpd_rr(src.code(), dest.code());
     }
     void ptest(const FloatRegister &lhs, const FloatRegister &rhs) {
@@ -1108,21 +1130,27 @@ class AssemblerX86Shared
         masm.ptest_rr(rhs.code(), lhs.code());
     }
     void ucomisd(const FloatRegister &lhs, const FloatRegister &rhs) {
+        JS_ASSERT(HasSSE2());
         masm.ucomisd_rr(rhs.code(), lhs.code());
     }
     void pcmpeqw(const FloatRegister &lhs, const FloatRegister &rhs) {
+        JS_ASSERT(HasSSE2());
         masm.pcmpeqw_rr(rhs.code(), lhs.code());
     }    
     void movd(const Register &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.movd_rr(src.code(), dest.code());
     }
     void movd(const FloatRegister &src, const Register &dest) {
+        JS_ASSERT(HasSSE2());
         masm.movd_rr(src.code(), dest.code());
     }
     void addsd(const FloatRegister &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.addsd_rr(src.code(), dest.code());
     }
     void addsd(const Operand &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         switch (src.kind()) {
           case Operand::FPREG:
             masm.addsd_rr(src.fpu(), dest.code());
@@ -1140,9 +1168,11 @@ class AssemblerX86Shared
         }
     }
     void subsd(const FloatRegister &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.subsd_rr(src.code(), dest.code());
     }
     void subsd(const Operand &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         switch (src.kind()) {
           case Operand::FPREG:
             masm.subsd_rr(src.fpu(), dest.code());
@@ -1155,9 +1185,11 @@ class AssemblerX86Shared
         }
     }
     void mulsd(const FloatRegister &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.mulsd_rr(src.code(), dest.code());
     }
     void mulsd(const Operand &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         switch (src.kind()) {
           case Operand::FPREG:
             masm.mulsd_rr(src.fpu(), dest.code());
@@ -1170,9 +1202,11 @@ class AssemblerX86Shared
         }
     }
     void divsd(const FloatRegister &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.divsd_rr(src.code(), dest.code());
     }
     void divsd(const Operand &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         switch (src.kind()) {
           case Operand::FPREG:
             masm.divsd_rr(src.fpu(), dest.code());
@@ -1185,20 +1219,25 @@ class AssemblerX86Shared
         }
     }
     void xorpd(const FloatRegister &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.xorpd_rr(src.code(), dest.code());
     }
     void orpd(const FloatRegister &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.orpd_rr(src.code(), dest.code());
     }
     void andpd(const FloatRegister &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.andpd_rr(src.code(), dest.code());
     }
     void sqrtsd(const FloatRegister &src, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.sqrtsd_rr(src.code(), dest.code());
     }
     void roundsd(const FloatRegister &src, const FloatRegister &dest,
                  JSC::X86Assembler::RoundingMode mode)
     {
+        JS_ASSERT(HasSSE41());
         masm.roundsd_rr(src.code(), dest.code(), mode);
     }
     void fstp(const Operand &src) {
diff --git a/js/src/ion/x86/Assembler-x86.h b/js/src/ion/x86/Assembler-x86.h
index 7b8200caa66c..22a9a2a9b224 100644
--- a/js/src/ion/x86/Assembler-x86.h
+++ b/js/src/ion/x86/Assembler-x86.h
@@ -432,6 +432,7 @@ class Assembler : public AssemblerX86Shared
     }
 
     void movsd(const double *dp, const FloatRegister &dest) {
+        JS_ASSERT(HasSSE2());
         masm.movsd_mr((const void *)dp, dest.code());
     }
 
@@ -448,6 +449,7 @@ class Assembler : public AssemblerX86Shared
         return masm.currentOffset();
     }
     CodeOffsetLabel movsdWithPatch(void *addr, FloatRegister dest) {
+        JS_ASSERT(HasSSE2());
         masm.movsd_mr(addr, dest.code());
         return masm.currentOffset();
     }
@@ -458,6 +460,7 @@ class Assembler : public AssemblerX86Shared
         return masm.currentOffset();
     }
     CodeOffsetLabel movsdWithPatch(FloatRegister dest, void *addr) {
+        JS_ASSERT(HasSSE2());
         masm.movsd_rm(dest.code(), addr);
         return masm.currentOffset();
     }
@@ -484,10 +487,12 @@ class Assembler : public AssemblerX86Shared
         return masm.currentOffset();
     }
     CodeOffsetLabel movssWithPatch(Address src, FloatRegister dest) {
+        JS_ASSERT(HasSSE2());
         masm.movss_mr_disp32(src.offset, src.base.code(), dest.code());
         return masm.currentOffset();
     }
     CodeOffsetLabel movsdWithPatch(Address src, FloatRegister dest) {
+        JS_ASSERT(HasSSE2());
         masm.movsd_mr_disp32(src.offset, src.base.code(), dest.code());
         return masm.currentOffset();
     }
@@ -506,10 +511,12 @@ class Assembler : public AssemblerX86Shared
         return masm.currentOffset();
     }
     CodeOffsetLabel movssWithPatch(FloatRegister src, Address dest) {
+        JS_ASSERT(HasSSE2());
         masm.movss_rm_disp32(src.code(), dest.offset, dest.base.code());
         return masm.currentOffset();
     }
     CodeOffsetLabel movsdWithPatch(FloatRegister src, Address dest) {
+        JS_ASSERT(HasSSE2());
         masm.movsd_rm_disp32(src.code(), dest.offset, dest.base.code());
         return masm.currentOffset();
     }
diff --git a/js/src/ion/x86/Trampoline-x86.cpp b/js/src/ion/x86/Trampoline-x86.cpp
index b813fa4162ad..7da46e0834b2 100644
--- a/js/src/ion/x86/Trampoline-x86.cpp
+++ b/js/src/ion/x86/Trampoline-x86.cpp
@@ -665,8 +665,14 @@ IonRuntime::generatePreBarrier(JSContext *cx, MIRType type)
 {
     MacroAssembler masm;
 
-    RegisterSet save = RegisterSet(GeneralRegisterSet(Registers::VolatileMask),
-                                   FloatRegisterSet(FloatRegisters::VolatileMask));
+    RegisterSet save;
+    if (cx->runtime->jitSupportsFloatingPoint) {
+        save = RegisterSet(GeneralRegisterSet(Registers::VolatileMask),
+                           FloatRegisterSet(FloatRegisters::VolatileMask));
+    } else {
+        save = RegisterSet(GeneralRegisterSet(Registers::VolatileMask),
+                           FloatRegisterSet());
+    }
     masm.PushRegsInMask(save);
 
     JS_ASSERT(PreBarrierReg == edx);
diff --git a/js/src/jit-test/jit_test.py b/js/src/jit-test/jit_test.py
index 0f4bdc855966..348c80cb672c 100755
--- a/js/src/jit-test/jit_test.py
+++ b/js/src/jit-test/jit_test.py
@@ -147,7 +147,7 @@ def main(argv):
                       ['--no-baseline'],
                       ['--no-baseline', '--ion-eager'],
                       ['--baseline-eager'],
-                      ['--baseline-eager', '--no-ti'],
+                      ['--baseline-eager', '--no-ti', '--no-fpu'],
                       # Below, equivalents the old shell flags: ,m,am,amd,n,mn,amn,amdn,mdn
                       ['--no-baseline', '--no-ion', '--no-jm', '--no-ti'],
                       ['--no-baseline', '--no-ion', '--no-ti'],
diff --git a/js/src/jit-test/tests/asm.js/testCall.js b/js/src/jit-test/tests/asm.js/testCall.js
index a8b7524e1832..8913c574d715 100644
--- a/js/src/jit-test/tests/asm.js/testCall.js
+++ b/js/src/jit-test/tests/asm.js/testCall.js
@@ -46,4 +46,4 @@ var rec = asmLink(asmCompile(USE_ASM+"function rec(i) { i=i|0; if (!i) return 0;
 assertEq(rec(100), 100);
 assertEq(rec(1000), 1000);
 assertThrowsInstanceOf(function() rec(100000000000), InternalError);
-assertEq(rec(10000), 10000);
+assertEq(rec(2000), 2000);
diff --git a/js/src/jsapi.cpp b/js/src/jsapi.cpp
index 3b343061ee63..3180e7f3e55e 100644
--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -686,6 +686,24 @@ JS_FRIEND_API(bool) JS::isGCEnabled() { return true; }
 
 static const JSSecurityCallbacks NullSecurityCallbacks = { };
 
+static bool
+JitSupportsFloatingPoint()
+{
+#if defined(JS_METHODJIT) || defined(JS_ION)
+    if (!JSC::MacroAssembler().supportsFloatingPoint())
+        return false;
+
+#if defined(JS_ION) && WTF_ARM_ARCH_VERSION == 6
+    if (!js::ion::hasVFP())
+        return false;
+#endif
+
+    return true;
+#else
+    return false;
+#endif
+}
+
 PerThreadData::PerThreadData(JSRuntime *runtime)
   : PerThreadDataFriendFields(),
     runtime_(runtime),
@@ -893,6 +911,7 @@ JSRuntime::JSRuntime(JSUseHelperThreads useHelperThreads)
     noGCOrAllocationCheck(0),
 #endif
     jitHardening(false),
+    jitSupportsFloatingPoint(false),
     ionPcScriptCache(NULL),
     threadPool(this),
     ctypesActivityCallback(NULL),
@@ -990,6 +1009,8 @@ JSRuntime::init(uint32_t maxbytes)
         return false;
 
     nativeStackBase = GetNativeStackBase();
+
+    jitSupportsFloatingPoint = JitSupportsFloatingPoint();
     return true;
 }
 
diff --git a/js/src/jscntxt.h b/js/src/jscntxt.h
index 3294cb3d1777..b3b0fad13626 100644
--- a/js/src/jscntxt.h
+++ b/js/src/jscntxt.h
@@ -1304,6 +1304,8 @@ struct JSRuntime : private JS::shadow::Runtime,
 
     bool                jitHardening;
 
+    bool                jitSupportsFloatingPoint;
+
     // Used to reset stack limit after a signaled interrupt (i.e. ionStackLimit_ = -1)
     // has been noticed by Ion/Baseline.
     void resetIonStackLimit() {
diff --git a/js/src/jsinfer.cpp b/js/src/jsinfer.cpp
index 3ac2212c0c51..663f400035c3 100644
--- a/js/src/jsinfer.cpp
+++ b/js/src/jsinfer.cpp
@@ -2382,31 +2382,6 @@ class TypeConstraintFreezeStack : public TypeConstraint
 // TypeCompartment
 /////////////////////////////////////////////////////////////////////
 
-static inline bool
-TypeInferenceSupported()
-{
-#ifdef JS_METHODJIT
-    // JM+TI will generate FPU instructions with TI enabled. As a workaround,
-    // we disable TI to prevent this on platforms which do not have FPU
-    // support.
-    JSC::MacroAssembler masm;
-    if (!masm.supportsFloatingPoint())
-        return false;
-#endif
-
-#if WTF_ARM_ARCH_VERSION == 6
-#ifdef  JS_ION
-    return js::ion::hasVFP();
-#else
-    // If building for ARMv6 targets, we can't be guaranteed an FPU,
-    // so we hardcode TI off for consistency (see bug 793740).
-    return false;
-#endif
-#endif
-
-    return true;
-}
-
 TypeCompartment::TypeCompartment()
 {
     PodZero(this);
@@ -2418,7 +2393,7 @@ TypeZone::init(JSContext *cx)
 {
     if (!cx ||
         !cx->hasOption(JSOPTION_TYPE_INFERENCE) ||
-        !TypeInferenceSupported())
+        !cx->runtime->jitSupportsFloatingPoint)
     {
         return;
     }
diff --git a/js/src/shell/js.cpp b/js/src/shell/js.cpp
index 013033e2f7f9..7c4e8286e8f2 100644
--- a/js/src/shell/js.cpp
+++ b/js/src/shell/js.cpp
@@ -5295,6 +5295,8 @@ main(int argc, char **argv, char **envp)
         || !op.addIntOption('\0', "baseline-uses-before-compile", "COUNT",
                             "Wait for COUNT calls or iterations before baseline-compiling "
                             "(default: 10)", -1)
+        || !op.addBoolOption('\0', "no-fpu", "Pretend CPU does not support floating-point operations "
+                             "to test JIT codegen (no-op on platforms other than x86).")
 #ifdef JSGC_GENERATIONAL
         || !op.addBoolOption('\0', "ggc", "Enable Generational GC")
 #endif
@@ -5329,6 +5331,11 @@ main(int argc, char **argv, char **envp)
         OOM_maxAllocations = op.getIntOption('A');
     if (op.getBoolOption('O'))
         OOM_printAllocationCount = true;
+
+#if defined(JS_CPU_X86)
+    if (op.getBoolOption("no-fpu"))
+        JSC::MacroAssembler::SetFloatingPointDisabled();
+#endif
 #endif
 
     /* Use the same parameters as the browser in xpcjsruntime.cpp. */