[llvm] 134cd79 - [Reland][PatternMatch] Add `m_[Shift]OrSelf` matchers. NFC. (#154375)

[via llvm-commits]

Author: Yingwei Zheng
Date: 2025-08-24T22:44:19+08:00
New Revision: 134cd7944814fd2cdcbcb908c7802a50d96683c8

URL: https://github.com/llvm/llvm-project/commit/134cd7944814fd2cdcbcb908c7802a50d96683c8
DIFF: https://github.com/llvm/llvm-project/commit/134cd7944814fd2cdcbcb908c7802a50d96683c8.diff

LOG: [Reland][PatternMatch] Add `m_[Shift]OrSelf` matchers. NFC. (#154375)

Address the comment
https://github.com/llvm/llvm-project/pull/147414/files#r2228612726.
As they are usually used to match integer packing patterns, it is enough
to handle constant shamts.

Relands https://github.com/llvm/llvm-project/pull/152924. This patch
removes the non-NFC changes in AggressiveInstCombine.

Added: 
    

Modified: 
    llvm/include/llvm/IR/PatternMatch.h
    llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
    llvm/unittests/IR/PatternMatch.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/IR/PatternMatch.h b/llvm/include/llvm/IR/PatternMatch.h
index 2ab652ca258c6..d68be03d4ba7d 100644
--- a/llvm/include/llvm/IR/PatternMatch.h
+++ b/llvm/include/llvm/IR/PatternMatch.h
@@ -1328,6 +1328,45 @@ inline BinaryOp_match<LHS, RHS, Instruction::AShr> m_AShr(const LHS &L,
   return BinaryOp_match<LHS, RHS, Instruction::AShr>(L, R);
 }
 
+template <typename LHS_t, unsigned Opcode> struct ShiftLike_match {
+  LHS_t L;
+  uint64_t &R;
+
+  ShiftLike_match(const LHS_t &LHS, uint64_t &RHS) : L(LHS), R(RHS) {}
+
+  template <typename OpTy> bool match(OpTy *V) const {
+    if (auto *Op = dyn_cast<BinaryOperator>(V)) {
+      if (Op->getOpcode() == Opcode)
+        return m_ConstantInt(R).match(Op->getOperand(1)) &&
+               L.match(Op->getOperand(0));
+    }
+    // Interpreted as shiftop V, 0
+    R = 0;
+    return L.match(V);
+  }
+};
+
+/// Matches shl L, ConstShAmt or L itself (R will be set to zero in this case).
+template <typename LHS>
+inline ShiftLike_match<LHS, Instruction::Shl> m_ShlOrSelf(const LHS &L,
+                                                          uint64_t &R) {
+  return ShiftLike_match<LHS, Instruction::Shl>(L, R);
+}
+
+/// Matches lshr L, ConstShAmt or L itself (R will be set to zero in this case).
+template <typename LHS>
+inline ShiftLike_match<LHS, Instruction::LShr> m_LShrOrSelf(const LHS &L,
+                                                            uint64_t &R) {
+  return ShiftLike_match<LHS, Instruction::LShr>(L, R);
+}
+
+/// Matches ashr L, ConstShAmt or L itself (R will be set to zero in this case).
+template <typename LHS>
+inline ShiftLike_match<LHS, Instruction::AShr> m_AShrOrSelf(const LHS &L,
+                                                            uint64_t &R) {
+  return ShiftLike_match<LHS, Instruction::AShr>(L, R);
+}
+
 template <typename LHS_t, typename RHS_t, unsigned Opcode,
           unsigned WrapFlags = 0, bool Commutable = false>
 struct OverflowingBinaryOp_match {

diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index ac03593dd5552..a13d3ceb61320 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -3640,16 +3640,11 @@ static bool matchSubIntegerPackFromVector(Value *V, Value *&Vec,
                                           int64_t &VecOffset,
                                           SmallBitVector &Mask,
                                           const DataLayout &DL) {
-  static const auto m_ConstShlOrSelf = [](const auto &Base, uint64_t &ShlAmt) {
-    ShlAmt = 0;
-    return m_CombineOr(m_Shl(Base, m_ConstantInt(ShlAmt)), Base);
-  };
-
   // First try to match extractelement -> zext -> shl
   uint64_t VecIdx, ShlAmt;
-  if (match(V, m_ConstShlOrSelf(m_ZExtOrSelf(m_ExtractElt(
-                                    m_Value(Vec), m_ConstantInt(VecIdx))),
-                                ShlAmt))) {
+  if (match(V, m_ShlOrSelf(m_ZExtOrSelf(m_ExtractElt(m_Value(Vec),
+                                                     m_ConstantInt(VecIdx))),
+                           ShlAmt))) {
     auto *VecTy = dyn_cast<FixedVectorType>(Vec->getType());
     if (!VecTy)
       return false;

diff  --git a/llvm/unittests/IR/PatternMatch.cpp b/llvm/unittests/IR/PatternMatch.cpp
index bb7cc0802b1df..972dac82d3331 100644
--- a/llvm/unittests/IR/PatternMatch.cpp
+++ b/llvm/unittests/IR/PatternMatch.cpp
@@ -2621,4 +2621,40 @@ TEST_F(PatternMatchTest, PtrAdd) {
   EXPECT_FALSE(match(OtherGEP, m_PtrAdd(m_Value(A), m_Value(B))));
 }
 
+TEST_F(PatternMatchTest, ShiftOrSelf) {
+  Type *I64Ty = Type::getInt64Ty(Ctx);
+  Constant *LHS = ConstantInt::get(I64Ty, 7);
+  Constant *ShAmt = ConstantInt::get(I64Ty, 16);
+  Value *Shl = IRB.CreateShl(LHS, ShAmt);
+  Value *LShr = IRB.CreateLShr(LHS, ShAmt);
+  Value *AShr = IRB.CreateAShr(LHS, ShAmt);
+  Value *Add = IRB.CreateAdd(LHS, LHS);
+
+  uint64_t ShAmtC;
+  Value *A;
+  EXPECT_TRUE(match(Shl, m_ShlOrSelf(m_Value(A), ShAmtC)));
+  EXPECT_EQ(A, LHS);
+  EXPECT_EQ(ShAmtC, 16U);
+
+  EXPECT_TRUE(match(Add, m_ShlOrSelf(m_Value(A), ShAmtC)));
+  EXPECT_EQ(A, Add);
+  EXPECT_EQ(ShAmtC, 0U);
+
+  EXPECT_TRUE(match(LShr, m_LShrOrSelf(m_Value(A), ShAmtC)));
+  EXPECT_EQ(A, LHS);
+  EXPECT_EQ(ShAmtC, 16U);
+
+  EXPECT_TRUE(match(Add, m_LShrOrSelf(m_Value(A), ShAmtC)));
+  EXPECT_EQ(A, Add);
+  EXPECT_EQ(ShAmtC, 0U);
+
+  EXPECT_TRUE(match(AShr, m_AShrOrSelf(m_Value(A), ShAmtC)));
+  EXPECT_EQ(A, LHS);
+  EXPECT_EQ(ShAmtC, 16U);
+
+  EXPECT_TRUE(match(Add, m_AShrOrSelf(m_Value(A), ShAmtC)));
+  EXPECT_EQ(A, Add);
+  EXPECT_EQ(ShAmtC, 0U);
+}
+
 } // anonymous namespace.