[llvm] [AArch64] Improve scheduling latency into Bundles (PR #86310)

[David Sherwood via llvm-commits]

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@@ -472,6 +472,45 @@ void AArch64Subtarget::overrideSchedPolicy(MachineSchedPolicy &Policy,
   Policy.DisableLatencyHeuristic = DisableLatencySchedHeuristic;
 }
 
+void AArch64Subtarget::adjustSchedDependency(
+    SUnit *Def, int DefOpIdx, SUnit *Use, int UseOpIdx, SDep &Dep,
+    const TargetSchedModel *SchedModel) const {
+  if (!SchedModel || Dep.getKind() != SDep::Kind::Data || !Dep.getReg() ||
+      !Def->isInstr() || !Use->isInstr() ||
+      (Def->getInstr()->getOpcode() != TargetOpcode::BUNDLE &&
+       Use->getInstr()->getOpcode() != TargetOpcode::BUNDLE))
+    return;
+
+  // If the Def is a BUNDLE, find the last instruction in the bundle that defs
+  // the register.
+  const MachineInstr *DefMI = Def->getInstr();
+  if (DefMI->getOpcode() == TargetOpcode::BUNDLE) {
+    Register Reg = DefMI->getOperand(DefOpIdx).getReg();
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david-arm wrote:

This might be a silly question, but is this always guaranteed to be a register?

https://github.com/llvm/llvm-project/pull/86310