[PatternMatch] Add a new m_Any that binds a value.

[lattner]

Summary

This is analogous to what LLVM's PatternMatch.h supports,
but LLVM calls it m_Value for both the binding and
nonbinding versions.

This is an upstream from CIRCT and is used there.

[lattner]

Thank you for the quick review!

mlir/include/mlir/IR/Matchers.h

matchOperandOrValueAtIndex(Operation *op, unsigned idx, MatcherClass &matcher) {
   return false;
 }
 
 /// Terminal matcher, always returns true.
 struct AnyValueMatcher {
   bool match(Value op) const { return true; }
 };
 
+/// Terminal matcher, always returns true.
+struct AnyCapturedValueMatcher {
+  Value *what;
+  AnyCapturedValueMatcher(Value *what) : what(what) {}
+  bool match(Value op) const {
+    *what = op;
+    return true;
+  }
+};
+
 /// Binds to a specific value and matches it.
 struct PatternMatcherValue {
   PatternMatcherValue(Value val) : value(val) {}
   bool match(Value val) const { return val == value; }
   Value value;
 };
 
 template <typename TupleT, class CallbackT, std::size_t... Is>

 
 template <typename OpType, typename... Matchers>
 auto m_Op(Matchers... matchers) {
   return detail::RecursivePatternMatcher<OpType, Matchers...>(matchers...);
 }
 
 namespace matchers {
 inline auto m_Any() { return detail::AnyValueMatcher(); }
+inline auto m_Any(Value *val) { return detail::AnyCapturedValueMatcher(val); }
 inline auto m_Val(Value v) { return detail::PatternMatcherValue(v); }
 } // namespace matchers
 
 } // end namespace mlir
 
 #endif // MLIR_MATCHERS_H