+// Check whether a boolean test is testing a boolean value generated by
+// X86ISD::SETCC. If so, return the operand of that SETCC and proper condition
+// code.
+//
+// Simplify the following patterns:
+// (Op (CMP (SETCC Cond EFLAGS) 1) EQ) or
+// (Op (CMP (SETCC Cond EFLAGS) 0) NEQ)
+// to (Op EFLAGS Cond)
+//
+// (Op (CMP (SETCC Cond EFLAGS) 0) EQ) or
+// (Op (CMP (SETCC Cond EFLAGS) 1) NEQ)
+// to (Op EFLAGS !Cond)
+//
+// where Op could be BRCOND or CMOV.
+//
+static SDValue BoolTestSetCCCombine(SDValue Cmp, X86::CondCode &CC) {
+ // Quit if not CMP and SUB with its value result used.
+ if (Cmp.getOpcode() != X86ISD::CMP &&
+ (Cmp.getOpcode() != X86ISD::SUB || Cmp.getNode()->hasAnyUseOfValue(0)))
+ return SDValue();
+
+ // Quit if not used as a boolean value.
+ if (CC != X86::COND_E && CC != X86::COND_NE)
+ return SDValue();
+
+ // Check CMP operands. One of them should be 0 or 1 and the other should be
+ // an SetCC or extended from it.
+ SDValue Op1 = Cmp.getOperand(0);
+ SDValue Op2 = Cmp.getOperand(1);
+
+ SDValue SetCC;
+ const ConstantSDNode* C = 0;
+ bool needOppositeCond = (CC == X86::COND_E);
+
+ if ((C = dyn_cast<ConstantSDNode>(Op1)))
+ SetCC = Op2;
+ else if ((C = dyn_cast<ConstantSDNode>(Op2)))
+ SetCC = Op1;
+ else // Quit if all operands are not constants.
+ return SDValue();
+
+ if (C->getZExtValue() == 1)
+ needOppositeCond = !needOppositeCond;
+ else if (C->getZExtValue() != 0)
+ // Quit if the constant is neither 0 or 1.
+ return SDValue();
+
+ // Skip 'zext' node.
+ if (SetCC.getOpcode() == ISD::ZERO_EXTEND)
+ SetCC = SetCC.getOperand(0);
+
+ // Quit if not SETCC.
+ // FIXME: So far we only handle the boolean value generated from SETCC. If
+ // there is other ways to generate boolean values, we need handle them here
+ // as well.
+ if (SetCC.getOpcode() != X86ISD::SETCC)
+ return SDValue();
+
+ // Set the condition code or opposite one if necessary.
+ CC = X86::CondCode(SetCC.getConstantOperandVal(0));
+ if (needOppositeCond)
+ CC = X86::GetOppositeBranchCondition(CC);
+
+ return SetCC.getOperand(1);
+}
+