Fix Some Comments + Restore Old Adjacency Matrix

Author: mmarjieh

llvm/include/llvm/CodeGen/MachinePipeliner.h

@@ -373,7 +373,7 @@ class NodeSet {
         }
       }
     }
-    // Handle a back-edge between a store and a load
+    // Handle a back-edge in loop carried dependencies
     SUnit *FirstNode = Nodes[0];
     SUnit *LastNode = Nodes[Nodes.size() - 1];
 

llvm/lib/CodeGen/MachinePipeliner.cpp

@@ -1680,19 +1680,13 @@ void SwingSchedulerDAG::Circuits::createAdjacencyStructure(
         Added.set(N);
       }
     }
-    // Order edges of the following:
-    // 1. Load -> Store
-    // 2. Store -> Load
-    // are treated as a back-edge in the adjacency matrix.
-    // Store after store was handled above.
+    // A chain edge between a store and a load is treated as a back-edge in the
+    // adjacency matrix.
     for (auto &PI : SUnits[i].Preds) {
-      if (PI.getKind() != SDep::Order ||
+      if (!SUnits[i].getInstr()->mayStore() ||
           !DAG->isLoopCarriedDep(&SUnits[i], PI, false))
         continue;
-      if ((SUnits[i].getInstr()->mayLoad() &&
-           PI.getSUnit()->getInstr()->mayStore()) ||
-          (SUnits[i].getInstr()->mayStore() &&
-           PI.getSUnit()->getInstr()->mayLoad())) {
+      if (PI.getKind() == SDep::Order && PI.getSUnit()->getInstr()->mayLoad()) {
         int N = PI.getSUnit()->NodeNum;
         if (!Added.test(N)) {
           AdjK[i].push_back(N);

llvm/test/CodeGen/PowerPC/sms-recmii.ll

@@ -1,4 +1,4 @@
-; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 4
+; REQUIRES: asserts
 ; RUN: llc < %s -mtriple=powerpc64le-unknown-linux-gnu -verify-machineinstrs\
 ; RUN:       -mcpu=pwr9 --ppc-enable-pipeliner --debug-only=pipeliner 2>&1 | FileCheck %s