[llvm] [TableGen] Add a backend to generate MacroFusion predicators (PR #72222)

[Pierre van Houtryve via llvm-commits]

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@@ -0,0 +1,199 @@
+//===--- MacroFusionPredicatorEmitter.cpp - Generator for Fusion ----===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// MacroFusionPredicatorEmitter implements a TableGen-driven predicators
+// generator for macro-op fusions.
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Pierre-vh wrote:

Maybe not the best place for this but can you give a quick explanation of where/how this is used? It's not immediately obvious, and if someone has to fix a bug here it'd be easier if there was an example of what this does.

The file overall is lacking docs, none of the methods/classes have any info about them. Just having a sentence or two about the intention behind them (unless it's obvious, e.g. `MacroFusionPredicatorEmitter`)  would be a nice thing.

https://github.com/llvm/llvm-project/pull/72222