[PATCH] D42878: [DAGCombiner] Pass the original load to ExtendSetCCUses not the turncate.

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: RKSimon, spatel, niravd.

This method is trying to use the truncate node to find which SETCC operand should be replaced directly with the extended load.

This used to work correctly because all uses of the original load were replaced by the truncate before this function was called. So this was used to effectively bypass the truncate and find the load under it.

All but one of the callers now call this before the truncate has replaced the laod so the setcc doesn't yet use the truncate. To account for this we should pass the original load instead.

I changed the order of that one caller to make this work there too.

I don't have a test case because this is probably hidden by later DAG combines causing the extend and truncate to cancel out. I assume this way is a little more efficient and matches what was originally intended.


Repository:
  rL LLVM

https://reviews.llvm.org/D42878

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp


Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -258,8 +258,9 @@
     SDValue PromoteExtend(SDValue Op);
     bool PromoteLoad(SDValue Op);
 
-    void ExtendSetCCUses(const SmallVectorImpl<SDNode *> &SetCCs, SDValue Trunc,
-                         SDValue ExtLoad, const SDLoc &DL,
+    void ExtendSetCCUses(const SmallVectorImpl<SDNode *> &SetCCs,
+                         SDValue OrigLoad, SDValue ExtLoad,
+                         const SDLoc &DL,
                          ISD::NodeType ExtType);
 
     /// Call the node-specific routine that knows how to fold each
@@ -7300,16 +7301,16 @@
 }
 
 void DAGCombiner::ExtendSetCCUses(const SmallVectorImpl<SDNode *> &SetCCs,
-                                  SDValue Trunc, SDValue ExtLoad,
+                                  SDValue OrigLoad, SDValue ExtLoad,
                                   const SDLoc &DL, ISD::NodeType ExtType) {
   // Extend SetCC uses if necessary.
   for (unsigned i = 0, e = SetCCs.size(); i != e; ++i) {
     SDNode *SetCC = SetCCs[i];
     SmallVector<SDValue, 4> Ops;
 
     for (unsigned j = 0; j != 2; ++j) {
       SDValue SOp = SetCC->getOperand(j);
-      if (SOp == Trunc)
+      if (SOp == OrigLoad)
         Ops.push_back(ExtLoad);
       else
         Ops.push_back(DAG.getNode(ExtType, DL, ExtLoad->getValueType(0), SOp));
@@ -7412,9 +7413,9 @@
   // with a truncate of the concatenated sextloaded vectors.
   SDValue Trunc =
       DAG.getNode(ISD::TRUNCATE, SDLoc(N0), N0.getValueType(), NewValue);
-  CombineTo(N0.getNode(), Trunc, NewChain);
-  ExtendSetCCUses(SetCCs, Trunc, NewValue, DL,
+  ExtendSetCCUses(SetCCs, N0, NewValue, DL,
                   (ISD::NodeType)N->getOpcode());
+  CombineTo(N0.getNode(), Trunc, NewChain);
   return SDValue(N, 0); // Return N so it doesn't get rechecked!
 }
 
@@ -7547,7 +7548,7 @@
                                        LN0->getMemOperand());
       SDValue Trunc = DAG.getNode(ISD::TRUNCATE, SDLoc(N0),
                                   N0.getValueType(), ExtLoad);
-      ExtendSetCCUses(SetCCs, Trunc, ExtLoad, DL, ISD::SIGN_EXTEND);
+      ExtendSetCCUses(SetCCs, N0, ExtLoad, DL, ISD::SIGN_EXTEND);
       // If the load value is used only by N, replace it via CombineTo N.
       bool NoReplaceTrunc = SDValue(LN0, 0).hasOneUse();
       CombineTo(N, ExtLoad);
@@ -7611,7 +7612,7 @@
         SDValue Trunc = DAG.getNode(ISD::TRUNCATE,
                                     SDLoc(N0.getOperand(0)),
                                     N0.getOperand(0).getValueType(), ExtLoad);
-        ExtendSetCCUses(SetCCs, Trunc, ExtLoad, DL, ISD::SIGN_EXTEND);
+        ExtendSetCCUses(SetCCs, N0, ExtLoad, DL, ISD::SIGN_EXTEND);
         bool NoReplaceTruncAnd = !N0.hasOneUse();
         bool NoReplaceTrunc = SDValue(LN0, 0).hasOneUse();
         CombineTo(N, And);
@@ -7857,7 +7858,7 @@
 
       SDValue Trunc = DAG.getNode(ISD::TRUNCATE, SDLoc(N0),
                                   N0.getValueType(), ExtLoad);
-      ExtendSetCCUses(SetCCs, Trunc, ExtLoad, SDLoc(N), ISD::ZERO_EXTEND);
+      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);
@@ -7913,7 +7914,7 @@
         SDValue Trunc = DAG.getNode(ISD::TRUNCATE,
                                     SDLoc(N0.getOperand(0)),
                                     N0.getOperand(0).getValueType(), ExtLoad);
-        ExtendSetCCUses(SetCCs, Trunc, ExtLoad, DL, ISD::ZERO_EXTEND);
+        ExtendSetCCUses(SetCCs, N0, ExtLoad, DL, ISD::ZERO_EXTEND);
         bool NoReplaceTruncAnd = !N0.hasOneUse();
         bool NoReplaceTrunc = SDValue(LN0, 0).hasOneUse();
         CombineTo(N, And);
@@ -8098,7 +8099,7 @@
                                        LN0->getMemOperand());
       SDValue Trunc = DAG.getNode(ISD::TRUNCATE, SDLoc(N0),
                                   N0.getValueType(), ExtLoad);
-      ExtendSetCCUses(SetCCs, Trunc, ExtLoad, SDLoc(N),
+      ExtendSetCCUses(SetCCs, N0, ExtLoad, SDLoc(N),
                       ISD::ANY_EXTEND);
       // If the load value is used only by N, replace it via CombineTo N.
       bool NoReplaceTrunc = N0.hasOneUse();


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