[llvm] [SCEV] Add initial pattern matching for SCEV constants. (NFC) (PR #119389)

[Florian Hahn via llvm-commits]

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@@ -0,0 +1,59 @@
+//===- ScalarEvolutionPatternMatch.h - Match on SCEVs -----------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file provides a simple and efficient mechanism for performing general
+// tree-based pattern matches on SCEVs, based on LLVM's IR pattern matchers.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_SCALAREVOLUTIONPATTERNMATCH_H
+#define LLVM_ANALYSIS_SCALAREVOLUTIONPATTERNMATCH_H
+
+#include "llvm/Analysis/ScalarEvolutionExpressions.h"
+
+namespace llvm {
+namespace SCEVPatternMatch {
+
+template <typename Val, typename Pattern>
+bool match(const SCEV *S, const Pattern &P) {
+  return P.match(S);
+}
+
+/// Match a specified integer value. \p BitWidth optionally specifies the
+/// bitwidth the matched constant must have. If it is 0, the matched constant
+/// can have any bitwidth.
+template <unsigned BitWidth = 0> struct specific_intval {
+  APInt Val;
+
+  specific_intval(APInt V) : Val(std::move(V)) {}
+
+  bool match(const SCEV *S) const {
+    const auto *C = dyn_cast<SCEVConstant>(S);
+    if (!C)
+      return false;
+
+    if (BitWidth != 0 && C->getAPInt().getBitWidth() != BitWidth)
+      return false;
+    return APInt::isSameValue(C->getAPInt(), Val);
+  }
+};
+
+inline specific_intval<0> m_scev_Zero() {
+  return specific_intval<0>(APInt(64, 0));
+}
+inline specific_intval<0> m_scev_One() {
+  return specific_intval<0>(APInt(64, 1));
+}
+inline specific_intval<0> m_scev_MinusOne() {
+  return specific_intval<0>(APInt(64, -1));
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fhahn wrote:

Yeah, updated to build on top of `PatternMatch::specific_intval64`, thanks

https://github.com/llvm/llvm-project/pull/119389