[Comb] Fix excessive const shifts causing crashes and invalid IR #8696
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The folders and canonicalizers for `comb.shl`, `comb.shru`, and `comb.shrs` perform unchecked `getZExtValue()` calls which can crash if the shift amount does not fit into 64 bits. The shift amount is also not clamped to the width of the result, which causes the shift to be replaced with ops that have a different type. Found with [VlogHammer], which turns out to be a very handy tool! Fixes #8694. Fixes #8695. [VlogHammer]: https://github.com/YosysHQ/VlogHammer
youngar
approved these changes
Jul 11, 2025
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The folders and canonicalizers for
comb.shl,comb.shru, andcomb.shrsperform uncheckedgetZExtValue()calls which can crash if the shift amount does not fit into 64 bits. The shift amount is also not clamped to the width of the result, which causes the shift to be replaced with ops that have a different type.Found with VlogHammer, which turns out to be a very handy tool!
Fixes #8694.
Fixes #8695.