IR Pass Trace

IR Pass Trace compares consecutive Python IR snapshots before and after compiler passes. It helps identify which functions a pass changed and whether the pass generated warnings.

Input requirements

The directory name must start with passes_dump and follow these conventions:

passes_dump_<timestamp>/
├── 00_frontend.py
├── 01_PassA.py
├── 01_PassA.log       # optional
├── 02_PassB.py
└── 03_PassC.py

• 00_frontend.py must exist;
• subsequent snapshots must follow NN_<PassName>.py;
• pass numbers must start at 1 and remain consecutive, with no missing or duplicate numbers;
• a matching .log file is optional and displays warnings for that pass.

Each pass compares the previous snapshot with the current pass snapshot. For example, 02_PassB.py is compared with 01_PassA.py.

Open IR Pass Trace

In the VS Code Explorer, right-click a passes_dump* directory and select IR Pass Trace. You can also navigate from the top of Chip Swimlane to an associated directory found by the extension.

Inspect changes

The left pane lists passes by number and reports added and removed line counts. The view supports:

• marking No-op passes and filtering to Changed or No-op passes;
• marking and displaying warnings from matching .log files;
• selecting the first changed pass by default;
• filtering differences by top-level function or class method;
• displaying both line-level and character-level differences;
• switching between Side by side and Stacked layouts;
• synchronized scrolling in the two-column layout;
• folding large unchanged sections and expanding individual or all sections;
• using j/k or the arrow keys to move between passes.

Recommended workflow

1. Enable the Changed filter to find passes that actually modify the IR;
2. filter by function to focus on the current operator entry point or a suspicious function.

For an interactive view of on-chip memory reuse in a pass dump, see Memory Reuse Analysis.

Note

IR Pass Trace is a read-only viewer. It does not edit or write back to files in passes_dump.