Allow setcc (sext setcc) [0|1] [eq|ne] -> setcc

[arsenm]

Summary

The cases where the inner setcc was directly compared
was handled, but not if the setcc type needs to be promoted
when comparing.

Remove redundant R600 handling of a subset of cases the existing
function handles.

[chandlerc]

lib/CodeGen/SelectionDAG/TargetLowering.cpp

1204

I would call it 'nestedSetCCCombine'?

1496

Why only sign_extend? if zext or anyext can't happen here, it seems worth a comment.

[arsenm]

lib/CodeGen/SelectionDAG/TargetLowering.cpp

1496

zext doesn't need to be handled because there is already a combine for (zext x) == C --> x == (trunc C). I'm not sure why that doesn't work for sext.

lib/CodeGen/SelectionDAG/TargetLowering.cpp

   return CN->isNullValue();
 }
 
+// setcc (setcc), [0|1], [eq|ne]  -> setcc
+static SDValue setCCSetCCCombine(const TargetLowering *TLI,
+                                 TargetLowering::DAGCombinerInfo &DCI,
+                                 SDLoc dl,
+                                 SDValue N0, const ConstantSDNode *N1C,
+                                 ISD::CondCode Cond) {
+  SelectionDAG &DAG = DCI.DAG;
+  EVT VT = N0.getValueType();
+
+  if (!TLI->isTypeLegal(VT) || !VT.bitsLE(N0.getValueType()))
+    return SDValue();
+
+  bool TrueWhenTrue = (Cond == ISD::SETEQ) ^ (N1C->getAPIntValue() != 1);
+  if (TrueWhenTrue)
+    return DAG.getNode(ISD::TRUNCATE, dl, VT, N0);
+
+  // Invert the condition.
+  ISD::CondCode CC = cast<CondCodeSDNode>(N0.getOperand(2))->get();
+  CC = ISD::getSetCCInverse(CC, N0.getOperand(0).getValueType().isInteger());
+  if (DCI.isBeforeLegalizeOps() ||
+      TLI->isCondCodeLegal(CC, N0.getOperand(0).getSimpleValueType()))
+    return DAG.getSetCC(dl, VT, N0.getOperand(0), N0.getOperand(1), CC);
+
+  return SDValue();
+}
+
 /// SimplifySetCC - Try to simplify a setcc built with the specified operands
 /// and cc. If it is unable to simplify it, return a null SDValue.
 SDValue

                           Cond);
     } else if ((N1C->isNullValue() || N1C->getAPIntValue() == 1) &&
                 (Cond == ISD::SETEQ || Cond == ISD::SETNE)) {
-      // SETCC (SETCC), [0|1], [EQ|NE]  -> SETCC
-      if (N0.getOpcode() == ISD::SETCC &&
-          isTypeLegal(VT) && VT.bitsLE(N0.getValueType())) {
-        bool TrueWhenTrue = (Cond == ISD::SETEQ) ^ (N1C->getAPIntValue() != 1);
-        if (TrueWhenTrue)
-          return DAG.getNode(ISD::TRUNCATE, dl, VT, N0);
-        // Invert the condition.
-        ISD::CondCode CC = cast<CondCodeSDNode>(N0.getOperand(2))->get();
-        CC = ISD::getSetCCInverse(CC,
-                                  N0.getOperand(0).getValueType().isInteger());
-        if (DCI.isBeforeLegalizeOps() ||
-            isCondCodeLegal(CC, N0.getOperand(0).getSimpleValueType()))
-          return DAG.getSetCC(dl, VT, N0.getOperand(0), N0.getOperand(1), CC);
+      if (N0.getOpcode() == ISD::SETCC) {
+        // setcc (setcc), [0|1], [eq|ne]  -> setcc
+        SDValue Ret = setCCSetCCCombine(this, DCI, dl, N0, N1C, Cond);
+        if (Ret)
+          return Ret;
+      } else if (N0.getOpcode() == ISD::SIGN_EXTEND) {
+        // setcc (sext (setcc)), [0|1], [eq|ne]  -> setcc
+        SDValue N00 = N0.getOperand(0);
+        if (N00.getOpcode() == ISD::SETCC) {
+          SDValue Ret = setCCSetCCCombine(this, DCI, dl, N00, N1C, Cond);
+          if (Ret)
+            return Ret;
+        }
       }
 
       if ((N0.getOpcode() == ISD::XOR ||

lib/Target/R600/SIISelLowering.cpp

                                             DAGCombinerInfo &DCI) const {
   SelectionDAG &DAG = DCI.DAG;
   SDLoc DL(N);
-  EVT VT = N->getValueType(0);
 
   switch (N->getOpcode()) {
-    default: return AMDGPUTargetLowering::PerformDAGCombine(N, DCI);
-    case ISD::SETCC: {
-      SDValue Arg0 = N->getOperand(0);
-      SDValue Arg1 = N->getOperand(1);
-      SDValue CC = N->getOperand(2);
-      ConstantSDNode * C = nullptr;
-      ISD::CondCode CCOp = dyn_cast<CondCodeSDNode>(CC)->get();
-
-      // i1 setcc (sext(i1), 0, setne) -> i1 setcc(i1, 0, setne)
-      if (VT == MVT::i1
-          && Arg0.getOpcode() == ISD::SIGN_EXTEND
-          && Arg0.getOperand(0).getValueType() == MVT::i1
-          && (C = dyn_cast<ConstantSDNode>(Arg1))
-          && C->isNullValue()
-          && CCOp == ISD::SETNE) {
-        return SimplifySetCC(VT, Arg0.getOperand(0),
-                             DAG.getConstant(0, MVT::i1), CCOp, true, DCI, DL);
-      }
-      break;
-    }
-
+  default:
+    return AMDGPUTargetLowering::PerformDAGCombine(N, DCI);
   case AMDGPUISD::CVT_F32_UBYTE0:
   case AMDGPUISD::CVT_F32_UBYTE1:
   case AMDGPUISD::CVT_F32_UBYTE2:

test/CodeGen/R600/setcc-opt.ll

   store i1 %icmp1, i1 addrspace(1)* %out
   ret void
 }
+
+; SI-LABEL: @sext_bool_icmp_eq
+; SI: V_CMP_EQ_I32
+; SI-NEXT: V_CNDMASK_B32
+; SI-NOT: CMP
+; SI-NOT: CNDMASK
+; SI: S_ENDPGM
+define void @sext_bool_icmp_eq(i1 addrspace(1)* %out, i32 %a, i32 %b) nounwind {
+  %icmp0 = icmp eq i32 %a, %b
+  %ext = sext i1 %icmp0 to i32
+  %icmp1 = icmp eq i32 %ext, 1
+  store i1 %icmp1, i1 addrspace(1)* %out
+  ret void
+}