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.
src/IROperator.cpp
Outdated
| @@ -502,7 +502,7 @@ Expr lossless_cast(Type t, Expr e) { | |||
| Expr a = lossless_cast(t.narrow(), sub->a); | |||
| 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
approved these changes
Mar 18, 2024
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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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Ready to land? |
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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.