Handle unoptimized branches in CodeFolding #7111
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kripken
approved these changes
Nov 25, 2024
src/passes/CodeFolding.cpp
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| void visitSwitch(Switch* curr) { | ||
| for (auto target : curr->targets) { | ||
| unoptimizables.insert(target); |
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Another option could be to use visitExpression and BranchUtils to rule out all branches but a normal Break, which would avoid special-casing BrOn and Switch. But lgtm as that might not be worth it.
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That's a good idea. That will handle resume and resume_throw as well.
tlively
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CodeFolding previously did not consider br_on_* instructions at all, so it would happily merge tails even if there were br_on_* branches to the same label with non-matching tails. Fix the bug by making any label targeted by any instruction not explicitly handled by CodeFolding unoptimizable. This will gracefully handle other branching instructions like `resume` and `resume_throw` as well. Folding these branches properly is left as future work. Also rename the test file from code-folding_enable-threads.wast to just code-folding.wast and enable all features instead of just threads. The old name was left over from when the test was originally ported to lit, and the new feature is necessary because the new test uses GC instructions.
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Updated the implementation and rebased this onto main so it can land before the more controversial change that prevents concrete If arms from being folded. |
kripken
approved these changes
Nov 25, 2024
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CodeFolding previously did not consider br_on_* instructions at all, so
it would happily merge tails even if there were br_on_* branches to the
same label with non-matching tails. Fix the bug by making any label
targeted by any instruction not explicitly handled by CodeFolding
unoptimizable. This will gracefully handle other branching instructions
like
resumeandresume_throwas well. Folding these branchesproperly is left as future work.
Also rename the test file from code-folding_enable-threads.wast to just
code-folding.wast and enable all features instead of just threads. The
old name was left over from when the test was originally ported to lit,
and the new feature is necessary because the new test uses GC
instructions.