Improvements for x87 stack handling

src/ia32/macro-assembler-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2500 matching lines @@
     ret(bytes_dropped);
   } else {
     pop(scratch);
     add(esp, Immediate(bytes_dropped));
     push(scratch);
     ret(0);
   }
 }
 
 
+void MacroAssembler::VerifyX87StackDepth(uint depth) {
+  // Make sure the floating point stack is either empty or has depth items.
+  ASSERT(depth <= 7);
+
+  // The top-of-stack (tos) is 7 if there is one item pushed.
+  int tos = (8 - depth) % 8;
+  const int kTopMask = 0x3800;
+  push(eax);
+  fwait();
+  fnstsw_ax();
+  and_(eax, kTopMask);
+  shr(eax, 11);
+  cmp(eax, Immediate(tos));
+  Label all_ok;
+  j(equal, &all_ok);
+  Check(equal, "Unexpected FPU stack depth after instruction");
+  bind(&all_ok);
+  fnclex();
+  pop(eax);
+}
+
+
 void MacroAssembler::Drop(int stack_elements) {
   if (stack_elements > 0) {
     add(esp, Immediate(stack_elements * kPointerSize));
   }
 }
 
 
 void MacroAssembler::Move(Register dst, Register src) {
   if (!dst.is(src)) {
     mov(dst, src);
@@ skipping 562 matching lines @@
   j(greater, &no_info_available);
   cmp(MemOperand(scratch_reg, -AllocationSiteInfo::kSize),
       Immediate(Handle<Map>(isolate()->heap()->allocation_site_info_map())));
   bind(&no_info_available);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32