--- a/js/src/assembler/assembler/AssemblerBufferWithConstantPool.h
+++ b/js/src/assembler/assembler/AssemblerBufferWithConstantPool.h
@@ -255,17 +255,28 @@ public:
     }
 
     void putIntWithConstantDouble(uint32_t insn, double constant)
     {
         flushIfNoSpaceFor(4, 8);
 
         m_loadOffsets.append(AssemblerBuffer::size());
         bool isReusable = false;
-        jsdpun dpun;
+
+        union DoublePun {
+            struct {
+#if defined(IS_LITTLE_ENDIAN) && !defined(FPU_IS_ARM_FPA)
+                uint32_t lo, hi;
+#else
+                uint32_t hi, lo;
+#endif
+            } s;
+            double d;
+        } dpun;
+
         dpun.d = constant;
         
         m_pool[m_numConsts] = dpun.s.lo;
         m_pool[m_numConsts+1] = dpun.s.hi;
         m_mask[m_numConsts] = static_cast<char>(isReusable ? ReusableConst : UniqueConst);
         m_mask[m_numConsts+1] = static_cast<char>(isReusable ? ReusableConst : UniqueConst);
 
         AssemblerBuffer::putInt(AssemblerType::patchConstantPoolLoad(insn, m_numConsts));

--- a/js/src/ion/arm/MacroAssembler-arm.cpp
+++ b/js/src/ion/arm/MacroAssembler-arm.cpp
@@ -1116,17 +1116,26 @@ void
 MacroAssemblerARM::ma_vneg(FloatRegister src, FloatRegister dest)
 {
     as_vneg(dest, src);
 }
 
 void
 MacroAssemblerARM::ma_vimm(double value, FloatRegister dest)
 {
-    jsdpun dpun;
+    union DoublePun {
+        struct {
+#if defined(IS_LITTLE_ENDIAN) && !defined(FPU_IS_ARM_FPA)
+            uint32_t lo, hi;
+#else
+            uint32_t hi, lo;
+#endif
+        } s;
+        double d;
+    } dpun;
     dpun.d = value;
     if ((dpun.s.lo) == 0) {
         if (dpun.s.hi == 0) {
             // to zero a register, load 1.0, then execute dN <- dN - dN
             VFPImm dblEnc(0x3FF00000);
             as_vimm(dest, dblEnc);
             as_vsub(dest, dest, dest);
             return;

--- a/js/src/ion/x86/CodeGenerator-x86.cpp
+++ b/js/src/ion/x86/CodeGenerator-x86.cpp
@@ -174,20 +174,23 @@ CodeGeneratorX86::linkAbsoluteLabels()
 
 bool
 CodeGeneratorX86::visitDouble(LDouble *ins)
 {
     const LDefinition *out = ins->getDef(0);
     const LConstantIndex *cindex = ins->getOperand(0)->toConstantIndex();
     const Value &v = graph.getConstant(cindex->index());
 
-    jsdpun dpun;
+    union DoublePun {
+        uint64_t u;
+        double d;
+    } dpun;
     dpun.d = v.toDouble();
 
-    if (dpun.u64 == 0) {
+    if (dpun.u == 0) {
         masm.xorpd(ToFloatRegister(out), ToFloatRegister(out));
         return true;
     }
 
     DeferredDouble *d = new DeferredDouble(cindex->index());
     if (!deferredDoubles_.append(d))
         return false;