[NFC] Extract common code for keying off of APInts

Author: rjmccall

include/swift/Basic/APIntMap.h

@@ -0,0 +1,54 @@
+//===--- APIntMap.h - A map with APInts as the keys -------------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// LLVM does not allow arbitrary APInts to be the keys of a DenseMap because
+// APInts are only comparable if they have the same bit-width.  This map
+// implementation assumes that its keys will always be constrained to their
+// minimum width, so it's not a general-purpose structure, but it does work.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_BASIC_APINTMAP_H
+#define SWIFT_BASIC_APINTMAP_H
+
+#include "llvm/ADT/APInt.h"
+#include "llvm/ADT/DenseMap.h"
+#include "swift/Basic/LLVM.h"
+
+namespace swift {
+
+struct WidthPreservingAPIntDenseMapInfo {
+  // For the special values, we use -1 with a bit-width that isn't minimal
+  // for the value, then use a parser that always produces values with
+  // minimal bit-widths so that we don't get a conflict.
+  static inline APInt getEmptyKey() {
+    return APInt::getAllOnesValue(/*bitwidth*/2);
+  }
+  static inline APInt getTombstoneKey() {
+    return APInt::getAllOnesValue(/*bitwidth*/3);
+  }
+
+  static unsigned getHashValue(const APInt &Key) {
+    return static_cast<unsigned>(hash_value(Key));
+  }
+
+  static bool isEqual(const APInt &LHS, const APInt &RHS) {
+    return LHS.getBitWidth() == RHS.getBitWidth() && LHS == RHS;
+  }
+};
+
+template <class Value>
+using APIntMap = llvm::DenseMap<APInt, Value, WidthPreservingAPIntDenseMapInfo>;
+
+}
+
+#endif

lib/Sema/TypeCheckSwitchStmt.cpp

@@ -20,7 +20,7 @@
 #include "swift/AST/Pattern.h"
 #include "swift/Basic/STLExtras.h"
 
-#include <llvm/ADT/APInt.h>
+#include "swift/Basic/APIntMap.h"
 #include <llvm/ADT/APFloat.h>
 
 #include <numeric>
@@ -31,22 +31,6 @@ using namespace swift;
 #define DEBUG_TYPE "TypeCheckSwitchStmt"
 
 namespace {
-  struct DenseMapAPIntKeyInfo {
-    static inline APInt getEmptyKey() { return APInt(); }
-
-    static inline APInt getTombstoneKey() {
-      return APInt::getAllOnesValue(/*bitwidth*/1);
-    }
-
-    static unsigned getHashValue(const APInt &Key) {
-      return static_cast<unsigned>(hash_value(Key));
-    }
-
-    static bool isEqual(const APInt &LHS, const APInt &RHS) {
-      return LHS.getBitWidth() == RHS.getBitWidth() && LHS == RHS;
-    }
-  };
-
   struct DenseMapAPFloatKeyInfo {
     static inline APFloat getEmptyKey() { return APFloat(APFloat::Bogus(), 1); }
     static inline APFloat getTombstoneKey() { return APFloat(APFloat::Bogus(), 2); }
@@ -858,7 +842,7 @@ namespace {
     TypeChecker &TC;
     const SwitchStmt *Switch;
     const DeclContext *DC;
-    llvm::DenseMap<APInt, Expr *, ::DenseMapAPIntKeyInfo> IntLiteralCache;
+    APIntMap<Expr *> IntLiteralCache;
     llvm::DenseMap<APFloat, Expr *, ::DenseMapAPFloatKeyInfo> FloatLiteralCache;
     llvm::DenseMap<StringRef, Expr *> StringLiteralCache;