[PATCH] D34571: [DAGCombine] Improve handling of insert_subvector of bitcast values

[Nirav Dave via Phabricator via llvm-commits]

niravd updated this revision to Diff 104211.
niravd added a comment.

Comment cleanup


https://reviews.llvm.org/D34571

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp


Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -15470,12 +15470,42 @@
   if (N1.isUndef())
     return N0;
 
+  // If we know is also an insert_subvector and we've the only use combine it first.
+  if (N0.hasOneUse() && N0->getOpcode() == ISD::INSERT_SUBVECTOR)
+    if (SDValue NN0 = visitINSERT_SUBVECTOR(N0.getNode()))
+      return DAG.getNode(ISD::INSERT_SUBVECTOR, SDLoc(N), VT, NN0, N1, N2);
+
   // If this is an insert of an extracted vector into an undef vector, we can
   // just use the input to the extract.
   if (N0.isUndef() && N1.getOpcode() == ISD::EXTRACT_SUBVECTOR &&
       N1.getOperand(1) == N2 && N1.getOperand(0).getValueType() == VT)
     return N1.getOperand(0);
 
+  // If inserting a bitcast values into an undef vector, w/ same num
+  // elements, we can just use the bitcast input of the extract.
+  if (N0.isUndef() && N1.getOpcode() == ISD::BITCAST &&
+      N1.getOperand(0).getOpcode() == ISD::EXTRACT_SUBVECTOR &&
+      N1.getOperand(0).getOperand(1) == N2 &&
+      N1.getOperand(0).getOperand(0).getValueType().getVectorNumElements() ==
+          VT.getVectorNumElements()) {
+    return DAG.getBitcast(VT, N1.getOperand(0).getOperand(0));
+  }
+
+  // If Both N1 and N2 are bitcast values on which insert_subvector
+  // makes sense, pull bitcast through the insert.
+  if (N0.getOpcode() == ISD::BITCAST && N1.getOpcode() == ISD::BITCAST) {
+    SDValue CN0 = N0.getOperand(0);
+    SDValue CN1 = N1.getOperand(0);
+    if (CN0.getValueType().getVectorElementType() ==
+            CN1.getValueType().getVectorElementType() &&
+        CN0.getValueType().getVectorNumElements() ==
+            VT.getVectorNumElements()) {
+      SDValue NewINSERT = DAG.getNode(ISD::INSERT_SUBVECTOR, SDLoc(N),
+                                      CN0.getValueType(), CN0, CN1, N2);
+      return DAG.getBitcast(VT, NewINSERT);
+    }
+  }
+
   // Combine INSERT_SUBVECTORs where we are inserting to the same index.
   // INSERT_SUBVECTOR( INSERT_SUBVECTOR( Vec, SubOld, Idx ), SubNew, Idx )
   // --> INSERT_SUBVECTOR( Vec, SubNew, Idx )


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