Reland "Fix phis for non-sse2 double values"

src/ia32/macro-assembler-ia32.cc

Index: src/ia32/macro-assembler-ia32.cc
diff --git a/src/ia32/macro-assembler-ia32.cc b/src/ia32/macro-assembler-ia32.cc
index fbfe9ddb8c86d6c46b9693ce3ac6dbfd6faddd9f..79248042b83073f71cef4de9d1cd293bc21eba2a 100644
--- a/src/ia32/macro-assembler-ia32.cc
+++ b/src/ia32/macro-assembler-ia32.cc
@@ -2798,6 +2798,8 @@ void MacroAssembler::Ret(int bytes_dropped, Register scratch) {
 void MacroAssembler::VerifyX87StackDepth(uint32_t depth) {
   // Make sure the floating point stack is either empty or has depth items.
   ASSERT(depth <= 7);
+  // This is a very expensive.
+  ASSERT(FLAG_debug_code && FLAG_enable_slow_asserts);
 
   // The top-of-stack (tos) is 7 if there is one item pushed.
   int tos = (8 - depth) % 8;