Use AliasAnalysis::pointsToConstantMemory in SDISel to avoid unnecessary
dependencies with constant load nodes. This allows them to be scheduled
freely.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54001 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index fdc3d25..ac9e399 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -2885,9 +2885,15 @@
return;
SDOperand Root;
+ bool ConstantMemory = false;
if (I.isVolatile())
+ // Serialize volatile loads with other side effects.
Root = getRoot();
- else {
+ else if (AA.pointsToConstantMemory(SV)) {
+ // Do not serialize (non-volatile) loads of constant memory with anything.
+ Root = DAG.getEntryNode();
+ ConstantMemory = true;
+ } else {
// Do not serialize non-volatile loads against each other.
Root = DAG.getRoot();
}
@@ -2905,12 +2911,14 @@
Chains[i] = L.getValue(1);
}
- SDOperand Chain = DAG.getNode(ISD::TokenFactor, MVT::Other,
- &Chains[0], NumValues);
- if (isVolatile)
- DAG.setRoot(Chain);
- else
- PendingLoads.push_back(Chain);
+ if (!ConstantMemory) {
+ SDOperand Chain = DAG.getNode(ISD::TokenFactor, MVT::Other,
+ &Chains[0], NumValues);
+ if (isVolatile)
+ DAG.setRoot(Chain);
+ else
+ PendingLoads.push_back(Chain);
+ }
setValue(&I, DAG.getMergeValues(DAG.getVTList(&ValueVTs[0], NumValues),
&Values[0], NumValues));