Slight improvement to fusion #86
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navahgar
approved these changes
Jul 29, 2024
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| // We only support fusing def ops that have exactly one use, for | ||
| // now. Special-case the uses of the def in | ||
| // tcp.bind_symbolic_shape |
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| } | ||
| } | ||
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| if (cannotFuse) | ||
| bool canFuse = false; |
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We have a canFuse above which is a function to check if the def and use can be fused. Can you rename this variable to avoid any confusion?
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good callout :) fixed.
| // 2. All those uses are in the same group as the current op | ||
| if (opIsInsideGroup && | ||
| llvm::all_of(otherUses, [&](Operation *userOp) { | ||
| return userOp->getParentRegion() == op->getParentRegion(); |
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This works because the op which is the use in this case is already in the group. That is not immediately clear when reading through the code. It is a very subtle. Can you add a comment to explain that?
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Yes. I had a bit of a longer comment later on. But I repeated it somewhat here just to be additionally clear.
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As discussed, a small improvement to the fusion algorithm to account for the case when we have multiple uses of a definition but all those uses already belong to the group we are in. This allows us to fuse "diamond patterns" of multiple uses into a single group. See the update to the lit test for the improvement.
Note that this still is not a "maximal" fusion which can create groups with multiple returns etc.