Add m_SelectCCLike matcher to match SELECT_CC or SELECT with SETCC (#149646)

Fix #147282 and  Follow-up to #148834

---------

Co-authored-by: Simon Pilgrim <[email protected]>

Author: houngkoungting

llvm/include/llvm/CodeGen/SDPatternMatch.h

@@ -578,6 +578,18 @@ m_InsertSubvector(const LHS &Base, const RHS &Sub, const IDX &Idx) {
   return TernaryOpc_match<LHS, RHS, IDX>(ISD::INSERT_SUBVECTOR, Base, Sub, Idx);
 }
 
+template <typename LTy, typename RTy, typename TTy, typename FTy, typename CCTy>
+inline auto m_SelectCC(const LTy &L, const RTy &R, const TTy &T, const FTy &F,
+                       const CCTy &CC) {
+  return m_Node(ISD::SELECT_CC, L, R, T, F, CC);
+}
+
+template <typename LTy, typename RTy, typename TTy, typename FTy, typename CCTy>
+inline auto m_SelectCCLike(const LTy &L, const RTy &R, const TTy &T,
+                           const FTy &F, const CCTy &CC) {
+  return m_AnyOf(m_Select(m_SetCC(L, R, CC), T, F), m_SelectCC(L, R, T, F, CC));
+}
+
 // === Binary operations ===
 template <typename LHS_P, typename RHS_P, bool Commutable = false,
           bool ExcludeChain = false>

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -4107,18 +4107,17 @@ SDValue DAGCombiner::visitSUB(SDNode *N) {
   // (sub x, ([v]select (uge x, y), y, 0)) -> (umin x, (sub x, y))
   if (N1.hasOneUse() && hasUMin(VT)) {
     SDValue Y;
-    if (sd_match(N1, m_Select(m_SetCC(m_Specific(N0), m_Value(Y),
-                                      m_SpecificCondCode(ISD::SETULT)),
-                              m_Zero(), m_Deferred(Y))) ||
-        sd_match(N1, m_Select(m_SetCC(m_Specific(N0), m_Value(Y),
-                                      m_SpecificCondCode(ISD::SETUGE)),
-                              m_Deferred(Y), m_Zero())) ||
-        sd_match(N1, m_VSelect(m_SetCC(m_Specific(N0), m_Value(Y),
-                                       m_SpecificCondCode(ISD::SETULT)),
-                               m_Zero(), m_Deferred(Y))) ||
-        sd_match(N1, m_VSelect(m_SetCC(m_Specific(N0), m_Value(Y),
-                                       m_SpecificCondCode(ISD::SETUGE)),
-                               m_Deferred(Y), m_Zero())))
+    auto MS0 = m_Specific(N0);
+    auto MVY = m_Value(Y);
+    auto MZ = m_Zero();
+    auto MCC1 = m_SpecificCondCode(ISD::SETULT);
+    auto MCC2 = m_SpecificCondCode(ISD::SETUGE);
+
+    if (sd_match(N1, m_SelectCCLike(MS0, MVY, MZ, m_Deferred(Y), MCC1)) ||
+        sd_match(N1, m_SelectCCLike(MS0, MVY, m_Deferred(Y), MZ, MCC2)) ||
+        sd_match(N1, m_VSelect(m_SetCC(MS0, MVY, MCC1), MZ, m_Deferred(Y))) ||
+        sd_match(N1, m_VSelect(m_SetCC(MS0, MVY, MCC2), m_Deferred(Y), MZ)))
+
       return DAG.getNode(ISD::UMIN, DL, VT, N0,
                          DAG.getNode(ISD::SUB, DL, VT, N0, Y));
   }

llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp

@@ -859,3 +859,35 @@ TEST_F(SelectionDAGPatternMatchTest, MatchZeroOneAllOnes) {
     EXPECT_TRUE(sd_match(Vec, DAG.get(), m_AllOnes(true)));
   }
 }
+
+TEST_F(SelectionDAGPatternMatchTest, MatchSelectCCLike) {
+  using namespace SDPatternMatch;
+
+  SDValue LHS = DAG->getConstant(1, SDLoc(), MVT::i32);
+  SDValue RHS = DAG->getConstant(2, SDLoc(), MVT::i32);
+  SDValue TVal = DAG->getConstant(3, SDLoc(), MVT::i32);
+  SDValue FVal = DAG->getConstant(4, SDLoc(), MVT::i32);
+  SDValue Select = DAG->getNode(ISD::SELECT_CC, SDLoc(), MVT::i32, LHS, RHS,
+                                TVal, FVal, DAG->getCondCode(ISD::SETLT));
+
+  ISD::CondCode CC = ISD::SETLT;
+  EXPECT_TRUE(sd_match(
+      Select, m_SelectCCLike(m_Specific(LHS), m_Specific(RHS), m_Specific(TVal),
+                             m_Specific(FVal), m_CondCode(CC))));
+}
+
+TEST_F(SelectionDAGPatternMatchTest, MatchSelectCC) {
+  using namespace SDPatternMatch;
+
+  SDValue LHS = DAG->getConstant(1, SDLoc(), MVT::i32);
+  SDValue RHS = DAG->getConstant(2, SDLoc(), MVT::i32);
+  SDValue TVal = DAG->getConstant(3, SDLoc(), MVT::i32);
+  SDValue FVal = DAG->getConstant(4, SDLoc(), MVT::i32);
+  SDValue Select = DAG->getNode(ISD::SELECT_CC, SDLoc(), MVT::i32, LHS, RHS,
+                                TVal, FVal, DAG->getCondCode(ISD::SETLT));
+
+  ISD::CondCode CC = ISD::SETLT;
+  EXPECT_TRUE(sd_match(Select, m_SelectCC(m_Specific(LHS), m_Specific(RHS),
+                                          m_Specific(TVal), m_Specific(FVal),
+                                          m_CondCode(CC))));
+}