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nim-works / phy

compiler and vm experiments
MIT License
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pass10: fix propagation of needed locals #48

Closed zerbina closed 1 month ago

zerbina commented 1 month ago

Summary

Fix a bug with propagation of needed locals in pass10 that resulted in crashes for locals needed across a loop edge.

Details

The test for detecting the loop start during backward propagation was wrong. It triggered immediately for the basic-block ending in the loop edge, thus disabling reiteration for the rest of the loop's basic-blocks, which resulted in incorrect needs sets.

The condition is corrected and a test case for reproducing the issue is added.

saem commented 1 month ago

FYI: fixed a tiny typo in the PR body.