[PATCH] D71180: [NFC][MacroFusion] Adding the assertion if someone want to fuse more than 2 instructions.

[qshanz via Phabricator via llvm-commits]

steven.zhang created this revision.
steven.zhang added reviewers: fhahn, evandro, jsji, PowerPC.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.

As discussed in https://reviews.llvm.org/D69998, we miss to create some dependency edges if chained more than 2 instructions. Adding an assertion here if someone want to chain more than 2 instructions.


https://reviews.llvm.org/D71180

Files:
  llvm/lib/CodeGen/MacroFusion.cpp


Index: llvm/lib/CodeGen/MacroFusion.cpp
===================================================================
--- llvm/lib/CodeGen/MacroFusion.cpp
+++ llvm/lib/CodeGen/MacroFusion.cpp
@@ -71,6 +71,13 @@
   if (!DAG.addEdge(&SecondSU, SDep(&FirstSU, SDep::Cluster)))
     return false;
 
+  // TODO - If we want to chain more than two instructions, we need to create
+  // artifical edges to make data dependencies from the FirstSU and dependencies
+  // of the SecondSU also dependent on other chained instructions, to prevent
+  // them from being scheduled into these chained instructions.
+  assert(hasLessThanNumFused(FirstSU, 2) &&
+         "Chain two instructions together at most");
+
   // Adjust the latency between both instrs.
   for (SDep &SI : FirstSU.Succs)
     if (SI.getSUnit() == &SecondSU)


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