Clarify the meaning of Shuffle::is_broadcast()#8158
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I was poking at the Shuffle node, and checking its usage, and it seems that despite the comment, Shuffles that return true for is_broadcast are not the same as a Broadcast node. Instead of repeating the input vector some number of times, it repeats a shuffle of the input vector. This means IRPrinter was incorrect. None of the other usages were bad. This PR makes this clearer in the comment, and fixes IRPrinter.
| Expr b = lossless_cast(t.narrow(), sub->b); | ||
| if (a.defined() && b.defined()) { | ||
| return cast(t, a) + cast(t, b); | ||
| return cast(t, a) - cast(t, b); |
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Oops, a local change from the other PR snuck in. Will revert.
steven-johnson
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Mar 18, 2024
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LGTM but IMHO we'd be better off renaming this method further; having two different things both named "broadcast" is needlessly confusing
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A Broadcast node is already capable of repeating vectors, so I actually think this shuffle pattern should be a Broadcast node wrapped around a smaller shuffle, but it's used in ways I don't entirely understand in HexagonOptimize, so it's not a trivial change. I was in the middle of trying to fix the lossless_cast bug though, so I though I'd at least fix the comment rather than get side-tracked. |
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I was poking at the Shuffle node, and checking its usage, and it seems that despite the comment, Shuffles that return true for is_broadcast are not the same as Broadcast nodes. Instead of repeating the input vector some number of times, it repeats a shuffle of the input vector. This means IRPrinter was incorrect. The other usages were fine.
This PR makes this clearer in the comment, and fixes IRPrinter.