PPC: Work-around to preserve sNan bit

src/compiler/ppc/code-generator-ppc.cc

Index: src/compiler/ppc/code-generator-ppc.cc
diff --git a/src/compiler/ppc/code-generator-ppc.cc b/src/compiler/ppc/code-generator-ppc.cc
index 28ff242f66b36f01fb23559509aaf24c2072c7d8..886319c7c48191b8ba9fac1018ff14e1ca3d2201 100644
--- a/src/compiler/ppc/code-generator-ppc.cc
+++ b/src/compiler/ppc/code-generator-ppc.cc
@@ -2346,8 +2346,23 @@ void CodeGenerator::AssembleMove(InstructionOperand* source,
       DoubleRegister dst = destination->IsFPRegister()
                                ? g.ToDoubleRegister(destination)
                                : kScratchDoubleReg;
-      double value = (src.type() == Constant::kFloat32) ? src.ToFloat32()
-                                                        : src.ToFloat64();
+      double value;
+// bit_cast of snan is converted to qnan on ia32/x64
+#if V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64
+      intptr_t valueInt = (src.type() == Constant::kFloat32)
+                              ? src.ToFloat32AsInt()
+                              : src.ToFloat64AsInt();
+      if (valueInt == ((src.type() == Constant::kFloat32)
+                           ? 2141192192

[john.yan, 2017/01/30 18:20:09]

using hex seems more readable.

+                           : 9196350439090552832)) {
+        value = bit_cast<double, int64_t>(0x7ff4000000000000L);
+      } else {
+#endif
+        value = (src.type() == Constant::kFloat32) ? src.ToFloat32()
+                                                   : src.ToFloat64();
+#if V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64
+      }
+#endif
       __ LoadDoubleLiteral(dst, value, kScratchReg);
       if (destination->IsFPStackSlot()) {
         __ StoreDouble(dst, g.ToMemOperand(destination), r0);