SelectionDAG: Clean up LegalizeSetCCCondCode() function

Interpreting the results of this function is not very intuitive, so I
cleaned it up to make it more clear whether or not a SETCC op was
legalized and how it was legalized (either by swapping LHS and RHS or
replacing with AND/OR).

This patch does change functionality in the LHS and RHS swapping case,
but unfortunately there are no in-tree tests for this.  However, this
patch is a prerequisite for R600 to take advantage of the LHS and RHS
swapping, so tests will be added in subsequent commits.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191600 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 51 insertions, 26 deletions

diff --git a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index a2527961e6..c58b8fd0ba 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -95,7 +95,7 @@ private:
                                      SDValue N1, SDValue N2,
                                      ArrayRef<int> Mask) const;
 
-  void LegalizeSetCCCondCode(EVT VT, SDValue &LHS, SDValue &RHS, SDValue &CC,
+  bool LegalizeSetCCCondCode(EVT VT, SDValue &LHS, SDValue &RHS, SDValue &CC,
                              SDLoc dl);
 
   SDValue ExpandLibCall(RTLIB::Libcall LC, SDNode *Node, bool isSigned);
@@ -1596,9 +1596,14 @@ void SelectionDAGLegalize::ExpandDYNAMIC_STACKALLOC(SDNode* Node,
 }
 
 /// LegalizeSetCCCondCode - Legalize a SETCC with given LHS and RHS and
-/// condition code CC on the current target. This routine expands SETCC with
-/// illegal condition code into AND / OR of multiple SETCC values.
-void SelectionDAGLegalize::LegalizeSetCCCondCode(EVT VT,
+/// condition code CC on the current target.
+/// If the SETCC has been legalized using AND / OR, then the legalized node
+/// will be stored in LHS and RHS and CC will be set to SDValue().
+/// If the SETCC has been legalized by using getSetCCSwappedOperands(),
+/// then the values of LHS and RHS will be swapped and CC will be set to the
+/// new condition.
+/// \returns true if the SetCC has been legalized, false if it hasn't.
+bool SelectionDAGLegalize::LegalizeSetCCCondCode(EVT VT,
                                                  SDValue &LHS, SDValue &RHS,
                                                  SDValue &CC,
                                                  SDLoc dl) {
@@ -1659,10 +1664,9 @@ void SelectionDAGLegalize::LegalizeSetCCCondCode(EVT VT,
         // different manner of supporting expanding these cases.
         llvm_unreachable("Don't know how to expand this condition!");
       }
-      LHS = DAG.getSetCC(dl, VT, RHS, LHS, InvCC);
-      RHS = SDValue();
-      CC = SDValue();
-      return;
+      std::swap(LHS, RHS);
+      CC = DAG.getCondCode(InvCC);
+      return true;
     }
 
     SDValue SetCC1, SetCC2;
@@ -1679,9 +1683,10 @@ void SelectionDAGLegalize::LegalizeSetCCCondCode(EVT VT,
     LHS = DAG.getNode(Opc, dl, VT, SetCC1, SetCC2);
     RHS = SDValue();
     CC  = SDValue();
-    break;
+    return true;
   }
   }
+  return false;
 }
 
 /// EmitStackConvert - Emit a store/load combination to the stack.  This stores
@@ -3620,10 +3625,16 @@ void SelectionDAGLegalize::ExpandNode(SDNode *Node) {
     Tmp1 = Node->getOperand(0);
     Tmp2 = Node->getOperand(1);
     Tmp3 = Node->getOperand(2);
-    LegalizeSetCCCondCode(Node->getValueType(0), Tmp1, Tmp2, Tmp3, dl);
+    bool Legalized = LegalizeSetCCCondCode(Node->getValueType(0), Tmp1, Tmp2,
+                                           Tmp3, dl);
+
+    if (Legalized) {
+      // If we exapanded the SETCC by swapping LHS and RHS, create a new SETCC
+      // node..
+      if (Tmp3.getNode())
+        Tmp1 = DAG.getNode(ISD::SETCC, dl, Node->getValueType(0),
+                           Tmp1, Tmp2, Tmp3);
 
-    // If we expanded the SETCC into an AND/OR, return the new node
-    if (Tmp2.getNode() == 0) {
       Results.push_back(Tmp1);
       break;
     }
@@ -3654,14 +3665,21 @@ void SelectionDAGLegalize::ExpandNode(SDNode *Node) {
     Tmp4 = Node->getOperand(3);   // False
     SDValue CC = Node->getOperand(4);
 
-    LegalizeSetCCCondCode(getSetCCResultType(Tmp1.getValueType()),
-                          Tmp1, Tmp2, CC, dl);
+    bool Legalized = LegalizeSetCCCondCode(
+        getSetCCResultType(Tmp1.getValueType()), Tmp1, Tmp2, CC, dl);
 
-    assert(!Tmp2.getNode() && "Can't legalize SELECT_CC with legal condition!");
-    Tmp2 = DAG.getConstant(0, Tmp1.getValueType());
-    CC = DAG.getCondCode(ISD::SETNE);
-    Tmp1 = DAG.getNode(ISD::SELECT_CC, dl, Node->getValueType(0), Tmp1, Tmp2,
-                       Tmp3, Tmp4, CC);
+    assert(Legalized && "Can't legalize SELECT_CC with legal condition!");
+    // If we exapanded the SETCC by swapping LHS and RHS, create a new SELECT_CC
+    // node and return it.
+    if (CC.getNode()) {
+      Tmp1 = DAG.getNode(ISD::SELECT_CC, dl, Node->getValueType(0),
+                         Tmp1, Tmp2, Tmp3, Tmp4, CC);
+    } else {
+      Tmp2 = DAG.getConstant(0, Tmp1.getValueType());
+      CC = DAG.getCondCode(ISD::SETNE);
+      Tmp1 = DAG.getNode(ISD::SELECT_CC, dl, Node->getValueType(0), Tmp1, Tmp2,
+                         Tmp3, Tmp4, CC);
+    }
     Results.push_back(Tmp1);
     break;
   }
@@ -3671,14 +3689,21 @@ void SelectionDAGLegalize::ExpandNode(SDNode *Node) {
     Tmp3 = Node->getOperand(3);              // RHS
     Tmp4 = Node->getOperand(1);              // CC
 
-    LegalizeSetCCCondCode(getSetCCResultType(Tmp2.getValueType()),
-                          Tmp2, Tmp3, Tmp4, dl);
+    bool Legalized = LegalizeSetCCCondCode(getSetCCResultType(
+        Tmp2.getValueType()), Tmp2, Tmp3, Tmp4, dl);
+    assert(Legalized && "Can't legalize BR_CC with legal condition!");
 
-    assert(!Tmp3.getNode() && "Can't legalize BR_CC with legal condition!");
-    Tmp3 = DAG.getConstant(0, Tmp2.getValueType());
-    Tmp4 = DAG.getCondCode(ISD::SETNE);
-    Tmp1 = DAG.getNode(ISD::BR_CC, dl, Node->getValueType(0), Tmp1, Tmp4, Tmp2,
-                       Tmp3, Node->getOperand(4));
+    // If we exapanded the SETCC by swapping LHS and RHS, create a new BR_CC
+    // node.
+    if (Tmp4.getNode()) {
+      Tmp1 = DAG.getNode(ISD::BR_CC, dl, Node->getValueType(0), Tmp1,
+                         Tmp4, Tmp2, Tmp3, Node->getOperand(4));
+    } else {
+      Tmp3 = DAG.getConstant(0, Tmp2.getValueType());
+      Tmp4 = DAG.getCondCode(ISD::SETNE);
+      Tmp1 = DAG.getNode(ISD::BR_CC, dl, Node->getValueType(0), Tmp1, Tmp4, Tmp2,
+                         Tmp3, Node->getOperand(4));
+    }
     Results.push_back(Tmp1);
     break;
   }