Increase ARM/MIPS simulators stack safety margin to 512 bytes

R=erik.corry@gmail.com
BUG=v8:1773

Review URL: http://codereview.chromium.org/8337014

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9686 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/simulator-arm.cc

@@ -1268,9 +1268,9 @@ void Simulator::WriteDW(int32_t addr, int32_t value1, int32_t value2) {
 
 // Returns the limit of the stack area to enable checking for stack overflows.
 uintptr_t Simulator::StackLimit() const {
-  // Leave a safety margin of 256 bytes to prevent overrunning the stack when
+  // Leave a safety margin of 512 bytes to prevent overrunning the stack when
   // pushing values.
-  return reinterpret_cast<uintptr_t>(stack_) + 256;
+  return reinterpret_cast<uintptr_t>(stack_) + 512;
 }
 
 

src/mips/simulator-mips.cc

@@ -1359,9 +1359,9 @@ void Simulator::WriteB(int32_t addr, int8_t value) {
 
 // Returns the limit of the stack area to enable checking for stack overflows.
 uintptr_t Simulator::StackLimit() const {
-  // Leave a safety margin of 256 bytes to prevent overrunning the stack when
+  // Leave a safety margin of 512 bytes to prevent overrunning the stack when
   // pushing values.
-  return reinterpret_cast<uintptr_t>(stack_) + 256;
+  return reinterpret_cast<uintptr_t>(stack_) + 512;
 }