Improve macOS AArch64 JIT stencils by relaxing GOT loads
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- Python
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Description
Proposal:
The AArch64 JIT has support for optimising pairs of instructions that load an address through the global offset table (GOT).
On Linux, the JIT optimiser recognises assembly like:
adrp x9, :got:__PyRuntime
ldr x9, [x9, :got_lo12:__PyRuntime]
On macOS, Clang uses a different syntax recognised by the Mach-O linker:
adrp x9, __PyRuntime@GOTPAGE
ldr x9, [x9, __PyRuntime@GOTPAGEOFF]
We can add support for this using the existing patch_aarch64_33rx() function just by adjusting the regex which would enable the same optimisation we already use on Linux:
adrp x9, <__PyRuntime page>
add x9, x9, <page offset>
This is a natural followup to #157040. I have a small patch ready once jit development is unblocked.
Benchmark:
On my M5 MacBook Pro this shows a 1.16% improvement on the pyperformance suite though results are very noisy. Probably best to re-run with the official benchmarking runners.
Expand for full benchmarking results
Has this already been discussed elsewhere?
This is a minor feature, which does not need previous discussion elsewhere
Links to previous discussion of this feature:
#148598, #148501, #157040 /cc @diegorusso
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start in Tools/jit/_optimizers.py at patch_aarch64_33rx() and compare the existing Linux GOT-load pattern with Clang's macOS syntax described here. Update the matching logic so the existing AArch64 optimisation applies, then run the pyperformance suite or the official benchmarking runners to check the result.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- macos, python
- Domain
- compilers, performance
- Issue type
- Feature
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Active
- Clarity
- Clearly specified
- Newbie friendliness
- 72/100