[DAGCombiner] Set the right SDLoc on a newly-created sextload (6/N)

This teaches tryToFoldExtOfLoad to set the right location on a
newly-created extload. With that in place, the logic for performing a
certain ([s|z]ext (load ...)) combine becomes identical for sexts and
zexts, and we can get rid of one copy of the logic.

The test case churn is due to dependencies on IROrders inherited from
the wrong SDLoc.

Part of: llvm.org/PR37262

Differential Revision: https://reviews.llvm.org/D46158

llvm-svn: 332118

1 files changed, 8 insertions, 38 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 3a49cce59c7..2a5ebcc6fc2 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7782,9 +7782,9 @@ static SDValue tryToFoldExtOfLoad(SelectionDAG &DAG, DAGCombiner &Combiner,
     return {};
 
   LoadSDNode *LN0 = cast<LoadSDNode>(N0);
-  SDValue ExtLoad =
-      DAG.getExtLoad(ExtLoadType, DL, VT, LN0->getChain(), LN0->getBasePtr(),
-                     N0.getValueType(), LN0->getMemOperand());
+  SDValue ExtLoad = DAG.getExtLoad(ExtLoadType, SDLoc(LN0), VT, LN0->getChain(),
+                                   LN0->getBasePtr(), N0.getValueType(),
+                                   LN0->getMemOperand());
   Combiner.ExtendSetCCUses(SetCCs, N0, ExtLoad, DL, ExtOpc);
   // If the load value is used only by N, replace it via CombineTo N.
   bool NoReplaceTrunc = SDValue(LN0, 0).hasOneUse();
@@ -8131,41 +8131,11 @@ SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) {
                        X, DAG.getConstant(Mask, DL, VT));
   }
 
-  // fold (zext (load x)) -> (zext (truncate (zextload x)))
-  // Only generate vector extloads when 1) they're legal, and 2) they are
-  // deemed desirable by the target.
-  if (ISD::isNON_EXTLoad(N0.getNode()) && ISD::isUNINDEXEDLoad(N0.getNode()) &&
-      ((!LegalOperations && !VT.isVector() &&
-        !cast<LoadSDNode>(N0)->isVolatile()) ||
-       TLI.isLoadExtLegal(ISD::ZEXTLOAD, VT, N0.getValueType()))) {
-    bool DoXform = true;
-    SmallVector<SDNode*, 4> SetCCs;
-    if (!N0.hasOneUse())
-      DoXform = ExtendUsesToFormExtLoad(VT, N, N0, ISD::ZERO_EXTEND, SetCCs,
-                                        TLI);
-    if (VT.isVector())
-      DoXform &= TLI.isVectorLoadExtDesirable(SDValue(N, 0));
-    if (DoXform) {
-      LoadSDNode *LN0 = cast<LoadSDNode>(N0);
-      SDValue ExtLoad = DAG.getExtLoad(ISD::ZEXTLOAD, SDLoc(LN0), VT,
-                                       LN0->getChain(),
-                                       LN0->getBasePtr(), N0.getValueType(),
-                                       LN0->getMemOperand());
-
-      ExtendSetCCUses(SetCCs, N0, ExtLoad, SDLoc(N), ISD::ZERO_EXTEND);
-      // If the load value is used only by N, replace it via CombineTo N.
-      bool NoReplaceTrunc = SDValue(LN0, 0).hasOneUse();
-      CombineTo(N, ExtLoad);
-      if (NoReplaceTrunc) {
-        DAG.ReplaceAllUsesOfValueWith(SDValue(LN0, 1), ExtLoad.getValue(1));
-      } else {
-        SDValue Trunc = DAG.getNode(ISD::TRUNCATE, SDLoc(N0),
-                                    N0.getValueType(), ExtLoad);
-        CombineTo(LN0, Trunc, ExtLoad.getValue(1));
-      }
-      return SDValue(N, 0); // Return N so it doesn't get rechecked!
-    }
-  }
+  // Try to simplify (zext (load x)).
+  if (SDValue foldedExt =
+          tryToFoldExtOfLoad(DAG, *this, TLI, VT, LegalOperations, N, N0,
+                             SDLoc(N), ISD::ZEXTLOAD, ISD::ZERO_EXTEND))
+    return foldedExt;
 
   // fold (zext (load x)) to multiple smaller zextloads.
   // Only on illegal but splittable vectors.