Feature/volatile#18
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Pull request overview
This PR introduces volatile variables (@v) as acquire/release-style synchronization objects across the interpreter and memory models, expands execution-graph provenance/conflict metadata, and adds a TikZ (.tex) execution-graph output option alongside the existing Graphviz (.dot) output. It also updates the Python test harness to support per-model expectation overrides embedded in example files.
Changes:
- Add parsing/AST support for
@volatileidentifiers and implement volatile acquire (read) / release (write) behavior in the interpreter and both linear/branching memory models. - Extend execution traces/graphs and conflict objects to carry source-event provenance; add TikZ execution-graph printing and CLI format selection.
- Add/adjust example programs and test harness logic to accommodate model-dependent accept/reject outcomes.
Reviewed changes
Copilot reviewed 39 out of 40 changed files in this pull request and generated 7 comments.
Show a summary per file
| File | Description |
|---|---|
| test_gitmem.py | Add per-model expectation overrides via // expect ... directives. |
| src/tikz.hh | Declare TikZ execution-graph printer. |
| src/tikz.cc | Implement TikZ execution-graph rendering. |
| src/thread_trace.hh | Add volatile read/write trace events and unlock g-predecessor tracking. |
| src/sync_state.hh | Add VolatileSyncState interface. |
| src/passes/statements.cc | Allow Volatile token in assignment/value forms. |
| src/passes/expressions.cc | Allow Volatile token as an expression operand. |
| src/parser.cc | Tokenize @name as Volatile. |
| src/memory_model.hh | Add volatile sync ops + model hooks; add global lock ordering flag. |
| src/linear/version_store.cc | Include source events in conflicts. |
| src/linear/memory_model.hh | Add volatile hooks; rename push to pullpush; global lock ordering true. |
| src/linear/memory_model.cc | Implement volatile acquire/release and new pull/push split. |
| src/lang.hh | Add Volatile token and grammar support. |
| src/interpreter.hh | Include TikZ/linear headers for execution-graph printing decisions. |
| src/interpreter.cc | Implement volatile eval + tracing; add global lock ordering predecessor; TikZ output path. |
| src/graphviz.hh | Add visitor hooks for volatile read/write nodes. |
| src/graphviz.cc | Render volatile read/write nodes and sync edges in Graphviz output. |
| src/graph.hh | Add volatile graph node types; extend unlock with conflict + g-predecessor. |
| src/gitmem.cc | Add --format option and adjust default output extension. |
| src/execution_state.hh | Add Volatile object storage and global last-g-push tracking. |
| src/execution_state.cc | Implement get_volatile; include volatiles in global-state equality. |
| src/conflict.hh | Add conflict source-event provenance plumbing. |
| src/branching/lazy/version_store.cc | Include source events in conflicts. |
| src/branching/eager/version_store.cc | Include source events in conflicts; add <queue> include. |
| src/branching/base_version_store.hh | Add VolatileState for branching volatile release tracking. |
| src/branching/base_memory_model.hh | Add volatile acquire/release hooks; create volatile state. |
| src/branching/base_memory_model.cc | Implement volatile acquire/release semantics for branching models. |
| examples/reject/semantics/linear/volatile_sync_conflict.gm | New volatile conflict example (linear reject). |
| examples/reject/semantics/linear/volatile_sync_conflict_two_vars.gm | New volatile conflict example (linear reject). |
| examples/reject/semantics/linear/volatile_sync_communicate_volatile.gm | New volatile communication example (linear reject). |
| examples/reject/semantics/branching/volatile_sync_conflict.gm | New volatile conflict example (branching reject; lazy override). |
| examples/reject/semantics/branching/volatile_sync_communicate_volatile.gm | New volatile communication example (branching reject). |
| examples/accept/semantics/linear/volatile.gm | New basic volatile example (linear accept). |
| examples/accept/semantics/linear/volatile_sync.gm | New volatile sync example (linear accept). |
| examples/accept/semantics/linear/volatile_sync_communicate.gm | New volatile sync communication example (linear accept). |
| examples/accept/semantics/branching/volatile.gm | New basic volatile example (branching accept). |
| examples/accept/semantics/branching/volatile_sync.gm | New volatile sync example (branching accept). |
| examples/accept/semantics/branching/volatile_sync_conflict_two_vars.gm | New two-volatile example (branching accept). |
| CMakeLists.txt | Add src/tikz.cc to build. |
| .gitignore | Ignore additional local/editor artifacts and .dot outputs. |
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| // In the linear model all unlocks push to the same g, so a lock on any | ||
| // variable follows the most recent unlock of ANY variable (not just this | ||
| // one). Use the global g-push predecessor when the per-lock one is absent. | ||
| auto lock_predecessor = (gctx.model->uses_global_lock_ordering() | ||
| && !lock.last_unlock_event) | ||
| ? gctx.last_g_push_event : lock.last_unlock_event; |
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| if (output_path.empty()) { | ||
| std::string ext = (output_format == "tikz") ? ".tex" : ".dot"; | ||
| output_path = input_path.stem().replace_extension(ext); | ||
| } |
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| #include "tikz.hh" | ||
| #include "overloaded.hh" | ||
| #include <fstream> | ||
| #include <unordered_map> | ||
| #include <map> | ||
| #include <algorithm> | ||
| #include <optional> | ||
| #include <cstdio> | ||
|
|
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| auto is_sync_node = [](const Node* nd) -> bool { | ||
| return dynamic_cast<const Start*>(nd) || dynamic_cast<const End*>(nd) | ||
| || dynamic_cast<const Spawn*>(nd) || dynamic_cast<const Join*>(nd) | ||
| || dynamic_cast<const Lock*>(nd) || dynamic_cast<const Unlock*>(nd); | ||
| }; |
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| } else if (auto* nd = dynamic_cast<const Write*>(n)) { | ||
| ev.label = "W(" + latex_escape(nd->var) + "$_{" + std::to_string(tid) + "}$) = " + std::to_string(nd->value); | ||
| } else if (auto* nd = dynamic_cast<const Read*>(n)) { | ||
| std::visit(overloaded{ | ||
| [&](const Read::SuccessfulRead& sr) { | ||
| ev.label = "R(" + latex_escape(nd->var) + "$_{" + std::to_string(tid) + "}$) = " + std::to_string(sr.value); | ||
| }, | ||
| [&](const Conflict&) { | ||
| ev.label = "R(" + latex_escape(nd->var) + "$_{" + std::to_string(tid) + "}$) = ?"; | ||
| ev.is_conflict = true; | ||
| } | ||
| }, nd->read_result); |
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| } else if (dynamic_cast<const Start*>(ev.node)) { | ||
| // g: start pulls | ||
| if (has_g_lane) | ||
| f << "\\draw[link oneway] (laneG |- " << ev.name << ") -- (" << ev.name << ");\n"; | ||
| } else if (dynamic_cast<const End*>(ev.node)) { | ||
| // g: end pulls + pushes | ||
| if (has_g_lane) | ||
| f << "\\PullPush{(" << ev.name << ")}{(laneG |- " << ev.name << ")}\n"; | ||
| } |
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| struct Unlock : Node { | ||
| const std::string var; | ||
| const std::optional<Conflict> conflict; | ||
| std::shared_ptr<const Node> g_predecessor; | ||
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| Unlock(const std::string var) : var(var) {} | ||
| Unlock(const std::string var, std::optional<Conflict> conflict = std::nullopt, | ||
| std::shared_ptr<const Node> g_predecessor = nullptr) | ||
| : var(var), conflict(conflict), g_predecessor(g_predecessor) {} | ||
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| void accept(Visitor *v) const override { v->visitUnlock(this); } |
EliasC
approved these changes
Jul 22, 2026
EliasC
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EliasC
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LGTM. Let's see if copilot finds anything
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Duplicate of examples/accept/semantics/linear/volatile_sync.gm
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Duplicate of examples/reject/semantics/linear/volatile_sync_conflict.gm
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Duplicate of examples/accept/semantics/branching/volatile_sync_conflict_two_vars.gm
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(Which is a bit strange since one is accept and the other is reject!)
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