[PATCH] D13733: Perform DIV, REM -> DIVREM combining for all affected nodes at once.

[A. Skrobov via llvm-commits]

tyomitch created this revision.
tyomitch added reviewers: RKSimon, eli.friedman.
tyomitch added a subscriber: llvm-commits.

If the nodes are converted to DIVREM one at a time, then the resulting DIVREM
may get legalized by the backend into something target-specific that we won't
be able to recognize and correlate with the remaining nodes.

This recovers most of the tests broken by the previous patch.

http://reviews.llvm.org/D13733

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp

Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2204,20 +2204,37 @@
 
   SDValue Op0 = Node->getOperand(0);
   SDValue Op1 = Node->getOperand(1);
+  SDValue combined;
   for (SDNode::use_iterator UI = Op0.getNode()->use_begin(),
          UE = Op0.getNode()->use_end(); UI != UE; ++UI) {
     SDNode *User = *UI;
-    if (User == Node)
+    if (User == Node || User->use_empty())
       continue;
-    // The other use might have been replaced with a divrem already.
-    if ((User->getOpcode() == OtherOpcode || User->getOpcode() == DivRemOpc) &&
+    // Convert the other matching node(s), too;
+    // otherwise, the DIVREM may get target-legalized into something
+    // target-specific that we won't be able to recognize.
+    unsigned UserOpc = User->getOpcode();
+    if ((UserOpc == Opcode || UserOpc == OtherOpcode || UserOpc == DivRemOpc) &&
         User->getOperand(0) == Op0 &&
         User->getOperand(1) == Op1) {
-      SDVTList VTs = DAG.getVTList(VT, VT);
-      return DAG.getNode(DivRemOpc, SDLoc(Node), VTs, Op0, Op1);
+      if (!combined) {
+        if (UserOpc == OtherOpcode) {
+          SDVTList VTs = DAG.getVTList(VT, VT);
+          combined = DAG.getNode(DivRemOpc, SDLoc(Node), VTs, Op0, Op1);
+        } else if (UserOpc == DivRemOpc) {
+          combined = SDValue(User, 0);
+        } else {
+          assert(UserOpc == Opcode);
+          continue;
+        }
+      }
+      if (UserOpc == ISD::SDIV || UserOpc == ISD::UDIV)
+        CombineTo(User, combined);
+      else if (UserOpc == ISD::SREM || UserOpc == ISD::UREM)
+        CombineTo(User, combined.getValue(1));
     }
   }
-  return SDValue();
+  return combined;
 }
 
 SDValue DAGCombiner::visitSDIV(SDNode *N) {


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