[DAG] Add SDPatternMatch::m_Select (#100686)

This will enable us to use SDPatternMatch with ISD::SELECT SDNodes in
 the future.

Author: michaelmaitland

llvm/include/llvm/CodeGen/SDPatternMatch.h

@@ -490,6 +490,12 @@ m_c_SetCC(const T0_P &LHS, const T1_P &RHS, const T2_P &CC) {
                                                          CC);
 }
 
+template <typename T0_P, typename T1_P, typename T2_P>
+inline TernaryOpc_match<T0_P, T1_P, T2_P>
+m_Select(const T0_P &Cond, const T1_P &T, const T2_P &F) {
+  return TernaryOpc_match<T0_P, T1_P, T2_P>(ISD::SELECT, Cond, T, F);
+}
+
 // === Binary operations ===
 template <typename LHS_P, typename RHS_P, bool Commutable = false,
           bool ExcludeChain = false>

llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp

@@ -131,6 +131,12 @@ TEST_F(SelectionDAGPatternMatchTest, matchTernaryOp) {
   SDValue ICMP_EQ01 = DAG->getSetCC(DL, MVT::i1, Op0, Op1, ISD::SETEQ);
   SDValue ICMP_EQ10 = DAG->getSetCC(DL, MVT::i1, Op1, Op0, ISD::SETEQ);
 
+  auto Int1VT = EVT::getIntegerVT(Context, 1);
+  SDValue Cond = DAG->getCopyFromReg(DAG->getEntryNode(), DL, 3, Int1VT);
+  SDValue T = DAG->getCopyFromReg(DAG->getEntryNode(), DL, 4, Int1VT);
+  SDValue F = DAG->getCopyFromReg(DAG->getEntryNode(), DL, 5, Int1VT);
+  SDValue Select = DAG->getSelect(DL, MVT::i1, Cond, T, F);
+
   using namespace SDPatternMatch;
   ISD::CondCode CC;
   EXPECT_TRUE(sd_match(ICMP_UGT, m_SetCC(m_Value(), m_Value(),
@@ -153,6 +159,13 @@ TEST_F(SelectionDAGPatternMatchTest, matchTernaryOp) {
                                             m_SpecificCondCode(ISD::SETEQ))));
   EXPECT_TRUE(sd_match(ICMP_EQ10, m_c_SetCC(m_Specific(Op0), m_Specific(Op1),
                                             m_SpecificCondCode(ISD::SETEQ))));
+
+  EXPECT_TRUE(sd_match(
+      Select, m_Select(m_Specific(Cond), m_Specific(T), m_Specific(F))));
+  EXPECT_FALSE(sd_match(
+      Select, m_Select(m_Specific(Cond), m_Specific(F), m_Specific(T))));
+  EXPECT_FALSE(sd_match(ICMP_EQ01, m_Select(m_Specific(Op0), m_Specific(Op1),
+                                            m_SpecificCondCode(ISD::SETEQ))));
 }
 
 TEST_F(SelectionDAGPatternMatchTest, matchBinaryOp) {