After replacing the runtime unwind context stack with explicit
completion records for try/finally dispatch, the distinction between
"handler" (catch) and "finalizer" (finally) in the exception handler
table is no longer meaningful at runtime.
handle_exception() checked handler first, then finalizer, but they
did the exact same thing (set the PC). When both were present, the
finalizer was dead code.
Collapse both fields into a single handler_offset (now non-optional,
since an entry always has a target), remove the finalizer concept
from BasicBlock, UnwindContext, and ExceptionHandlers, and simplify
handle_exception() to a direct assignment.
The runtime unwind context stack was pushed by EnterUnwindContext
and popped by LeaveUnwindContext. With both opcodes removed, it is
no longer read or written by anything.
Remove UnwindInfo, the unwind_contexts vector, its GC visit loop,
its copy in ExecutionContext::copy(), and the VERIFY assertions that
referenced it in handle_exception() and catch_exception().
Replace the saved_lexical_environments stack in ExecutionContextRareData
with explicit register-based environment tracking. Environments are now
stored in registers and restored via SetLexicalEnvironment, making the
environment flow visible in bytecode.
Key changes:
- Add GetLexicalEnvironment and SetLexicalEnvironment opcodes
- CreateLexicalEnvironment takes explicit parent and dst operands
- EnterObjectEnvironment stores new environment in a dst register
- NewClass takes an explicit class_environment operand
- Remove LeaveLexicalEnvironment opcode (instead: SetLexicalEnvironment)
- Remove saved_lexical_environments from ExecutionContextRareData
- Use a reserved register for the saved lexical environment to avoid
dominance issues with lazily-emitted GetLexicalEnvironment
Bytecode source map entries are always added in order of increasing
bytecode offset, and lookups only happen during error handling (a cold
path). This makes a sorted vector with binary search a better fit than
a hash map.
This change reduces memory overhead and speeds up bytecode generation
by avoiding hash table operations during compilation. Lookups remain
fast via binary search, and since source_range_at() is only called
when generating stack traces, the O(log n) lookup is acceptable.
Add VERIFY guards to catch bytecode programs that exceed u32::max bytes
and narrow the bytecode_offset parameter in add_source_map_entry() to
u32. This is a preparatory change for optimizing source map storage.
This first pass only applies to the following two cases:
- Public functions returning a view type into an object they own
- Public ctors storing a view type
This catches a grand total of one (1) issue, which is fixed in
the previous commit.
This reverts commit c14173f651. We
should only annotate the minimum number of symbols that external
consumers actually use, so I am starting from scratch to do that
Resulting in a massive rename across almost everywhere! Alongside the
namespace change, we now have the following names:
* JS::NonnullGCPtr -> GC::Ref
* JS::GCPtr -> GC::Ptr
* JS::HeapFunction -> GC::Function
* JS::CellImpl -> GC::Cell
* JS::Handle -> GC::Root
