Bug 95784 – BytecodeGenerator::resolve is unnecessarily pessimistic

• Status: NEW
• Component: JavaScriptCore

[Oliver Hunt]

Currently BytecodeGenerator::resolve does:
   // Cases where we cannot statically optimize the lookup.
   if (property == propertyNames().arguments || !canOptimizeNonLocals())
       return ResolveResult::dynamicResolve(0);

   ScopeChainIterator iter = m_scope->begin();
   ScopeChainIterator end = m_scope->end();
   size_t depth = 0;
   size_t depthOfFirstScopeWithDynamicChecks = 0;
   unsigned flags = 0;

It should be possible to make it:
   // Cases where we cannot statically optimize the lookup.
   if (property == propertyNames().arguments)
       return ResolveResult::dynamicResolve(0);

   ScopeChainIterator iter = m_scope->begin();
   ScopeChainIterator end = m_scope->end();
   size_t depth = 0;
   size_t depthOfFirstScopeWithDynamicChecks = 0;
   unsigned flags = canOptimizeNonLocals() ? 0 : ResolveResult::DynamicFlag;

The only thing of obvious concern is that resolve_dynamic (and related thingies) may not deal well with the idea that the top scope chain may itself need to be checked