[PatternMatch] Add m_PtrAdd() matcher (NFC)

This matches a getelementptr i8 instruction or constant expression,
with a given pointer operand and index.

Author: nikic

llvm/include/llvm/IR/PatternMatch.h

@@ -1614,6 +1614,21 @@ struct m_SplatOrUndefMask {
   }
 };
 
+template <typename PointerOpTy, typename OffsetOpTy> struct PtrAdd_match {
+  PointerOpTy PointerOp;
+  OffsetOpTy OffsetOp;
+
+  PtrAdd_match(const PointerOpTy &PointerOp, const OffsetOpTy &OffsetOp)
+      : PointerOp(PointerOp), OffsetOp(OffsetOp) {}
+
+  template <typename OpTy> bool match(OpTy *V) {
+    auto *GEP = dyn_cast<GEPOperator>(V);
+    return GEP && GEP->getSourceElementType()->isIntegerTy(8) &&
+           PointerOp.match(GEP->getPointerOperand()) &&
+           OffsetOp.match(GEP->idx_begin()->get());
+  }
+};
+
 /// Matches ShuffleVectorInst independently of mask value.
 template <typename V1_t, typename V2_t>
 inline TwoOps_match<V1_t, V2_t, Instruction::ShuffleVector>
@@ -1647,6 +1662,13 @@ inline auto m_GEP(const OperandTypes &...Ops) {
   return AnyOps_match<Instruction::GetElementPtr, OperandTypes...>(Ops...);
 }
 
+/// Matches GEP with i8 source element type
+template <typename PointerOpTy, typename OffsetOpTy>
+inline PtrAdd_match<PointerOpTy, OffsetOpTy>
+m_PtrAdd(const PointerOpTy &PointerOp, const OffsetOpTy &OffsetOp) {
+  return PtrAdd_match<PointerOpTy, OffsetOpTy>(PointerOp, OffsetOp);
+}
+
 //===----------------------------------------------------------------------===//
 // Matchers for CastInst classes
 //

llvm/unittests/IR/PatternMatch.cpp

@@ -1847,4 +1847,26 @@ TEST_F(PatternMatchTest, ConstExpr) {
   EXPECT_TRUE(match(V, m_ConstantExpr()));
 }
 
+TEST_F(PatternMatchTest, PtrAdd) {
+  Type *PtrTy = PointerType::getUnqual(Ctx);
+  Type *IdxTy = Type::getInt64Ty(Ctx);
+  Constant *Null = Constant::getNullValue(PtrTy);
+  Constant *Offset = ConstantInt::get(IdxTy, 42);
+  Value *PtrAdd = IRB.CreatePtrAdd(Null, Offset);
+  Value *OtherGEP = IRB.CreateGEP(IdxTy, Null, Offset);
+  Value *PtrAddConst =
+      ConstantExpr::getGetElementPtr(Type::getInt8Ty(Ctx), Null, Offset);
+
+  Value *A, *B;
+  EXPECT_TRUE(match(PtrAdd, m_PtrAdd(m_Value(A), m_Value(B))));
+  EXPECT_EQ(A, Null);
+  EXPECT_EQ(B, Offset);
+
+  EXPECT_TRUE(match(PtrAddConst, m_PtrAdd(m_Value(A), m_Value(B))));
+  EXPECT_EQ(A, Null);
+  EXPECT_EQ(B, Offset);
+
+  EXPECT_FALSE(match(OtherGEP, m_PtrAdd(m_Value(A), m_Value(B))));
+}
+
 } // anonymous namespace.