C++: Disable _some_ constant folding in IR #15969
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jketema
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…umberOfNestedBinaryOperands').
This reverts commit f36b483.
…no longer constant folded by IR construction.
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DCA showed three FPs caused by us no longer realizing some code was dead in some really ugly php code. I've pushed 458ee13 to fix this. Locally this fixes those FPs. I'm running another DCA now to confirm this 🤞 |
jketema
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In #14210 Alex tried to disable close to all constant folding in IR generation. This made us hit some really complex cases (see the corresponding internal issue), which meant we had to back out of this approach.
This PR does the minimal changes necessary to fix the original issue: being able to select the dataflow node for
1(or2) in an expression such as1 | 2. We do this by disabling constant folding for binary operations only. In addition, we only disable it for "small binary operations" (currently defined as an operation with less than 50 operands).Unsurprisingly, most binary operations are "small". Here's the distribution on Wireshark (with a threshold line at 50 to make it easy to spot which ones we fold and which ones we don't):
I imagine we could make this threshold a lot bigger, but this seems to be the safe way to go about this.