[llvm] r324274 - [SDAG] Legalize all CondCodes by inverting them and/or swapping operands

[Krzysztof Parzyszek via llvm-commits]

Author: kparzysz
Date: Mon Feb  5 13:27:16 2018
New Revision: 324274

URL: http://llvm.org/viewvc/llvm-project?rev=324274&view=rev
Log:
[SDAG] Legalize all CondCodes by inverting them and/or swapping operands

Differential Revision: https://reviews.llvm.org/D42788

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp?rev=324274&r1=324273&r2=324274&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp Mon Feb  5 13:27:16 2018
@@ -1623,6 +1623,7 @@ bool SelectionDAGLegalize::LegalizeSetCC
   MVT OpVT = LHS.getSimpleValueType();
   ISD::CondCode CCCode = cast<CondCodeSDNode>(CC)->get();
   NeedInvert = false;
+  bool NeedSwap = false;
   switch (TLI.getCondCodeAction(CCCode, OpVT)) {
   default: llvm_unreachable("Unknown condition code action!");
   case TargetLowering::Legal:
@@ -1635,6 +1636,22 @@ bool SelectionDAGLegalize::LegalizeSetCC
       CC = DAG.getCondCode(InvCC);
       return true;
     }
+    // Swapping operands didn't work. Try inverting the condition.
+    InvCC = getSetCCInverse(CCCode, OpVT.isInteger());
+    if (!TLI.isCondCodeLegal(InvCC, OpVT)) {
+      // If inverting the condition is not enough, try swapping operands
+      // on top of it.
+      InvCC = ISD::getSetCCSwappedOperands(InvCC);
+      NeedSwap = true;
+    }
+    if (TLI.isCondCodeLegal(InvCC, OpVT)) {
+      CC = DAG.getCondCode(InvCC);
+      NeedInvert = true;
+      if (NeedSwap)
+        std::swap(LHS, RHS);
+      return true;
+    }
+
     ISD::CondCode CC1 = ISD::SETCC_INVALID, CC2 = ISD::SETCC_INVALID;
     unsigned Opc = 0;
     switch (CCCode) {
@@ -1676,20 +1693,10 @@ bool SelectionDAGLegalize::LegalizeSetCC
     case ISD::SETGT:
     case ISD::SETGE:
     case ISD::SETLT:
-      // We only support using the inverted operation, which is computed above
-      // and not a different manner of supporting expanding these cases.
-      llvm_unreachable("Don't know how to expand this condition!");
     case ISD::SETNE:
     case ISD::SETEQ:
-      // Try inverting the result of the inverse condition.
-      InvCC = CCCode == ISD::SETEQ ? ISD::SETNE : ISD::SETEQ;
-      if (TLI.isCondCodeLegal(InvCC, OpVT)) {
-        CC = DAG.getCondCode(InvCC);
-        NeedInvert = true;
-        return true;
-      }
-      // If inverting the condition didn't work then we have no means to expand
-      // the condition.
+      // If all combinations of inverting the condition and swapping operands
+      // didn't work then we have no means to expand the condition.
       llvm_unreachable("Don't know how to expand this condition!");
     }