[ADT] Simplify and optimize StringSwitch

This change improves incremental rebuild performance on dual Xeon 8168
machines by 54%. This change also improves run time code gen by not
forcing the case values to be lvalues.

llvm-svn: 326109

3 files changed, 82 insertions, 107 deletions

diff --git a/llvm/include/llvm/ADT/StringRef.h b/llvm/include/llvm/ADT/StringRef.h
index f6c93a858db..3d2417acead 100644
--- a/llvm/include/llvm/ADT/StringRef.h
+++ b/llvm/include/llvm/ADT/StringRef.h
@@ -855,6 +855,10 @@ namespace llvm {
   /// constexpr StringLiteral S("test");
   ///
   class StringLiteral : public StringRef {
+  private:
+    constexpr StringLiteral(const char *Str, size_t N) : StringRef(Str, N) {
+    }
+
   public:
     template <size_t N>
     constexpr StringLiteral(const char (&Str)[N])
@@ -867,6 +871,12 @@ namespace llvm {
 #endif
         : StringRef(Str, N - 1) {
     }
+
+    // Explicit construction for strings like "foo\0bar".
+    template <size_t N>
+    static constexpr StringLiteral withInnerNUL(const char (&Str)[N]) {
+      return StringLiteral(Str, N - 1);
+    }
   };
 
   /// @name StringRef Comparison Operators
diff --git a/llvm/include/llvm/ADT/StringSwitch.h b/llvm/include/llvm/ADT/StringSwitch.h
index 75577b7738b..5fad2476181 100644
--- a/llvm/include/llvm/ADT/StringSwitch.h
+++ b/llvm/include/llvm/ADT/StringSwitch.h
@@ -42,16 +42,16 @@ namespace llvm {
 template<typename T, typename R = T>
 class StringSwitch {
   /// \brief The string we are matching.
-  StringRef Str;
+  const StringRef Str;
 
   /// \brief The pointer to the result of this switch statement, once known,
   /// null before that.
-  const T *Result;
+  Optional<T> Result;
 
 public:
   LLVM_ATTRIBUTE_ALWAYS_INLINE
   explicit StringSwitch(StringRef S)
-  : Str(S), Result(nullptr) { }
+  : Str(S), Result() { }
 
   // StringSwitch is not copyable.
   StringSwitch(const StringSwitch &) = delete;
@@ -61,196 +61,159 @@ public:
     *this = std::move(other);
   }
   StringSwitch &operator=(StringSwitch &&other) {
-    Str = other.Str;
-    Result = other.Result;
+    Str = std::move(other.Str);
+    Result = std::move(other.Result);
     return *this;
   }
 
   ~StringSwitch() = default;
 
   // Case-sensitive case matchers
-  template<unsigned N>
   LLVM_ATTRIBUTE_ALWAYS_INLINE
-  StringSwitch& Case(const char (&S)[N], const T& Value) {
-    assert(N);
-    if (!Result && N-1 == Str.size() &&
-        (N == 1 || std::memcmp(S, Str.data(), N-1) == 0)) {
-      Result = &Value;
+  StringSwitch &Case(StringLiteral S, T Value) {
+    if (!Result && Str == S) {
+      Result = std::move(Value);
     }
     return *this;
   }
 
-  template<unsigned N>
   LLVM_ATTRIBUTE_ALWAYS_INLINE
-  StringSwitch& EndsWith(const char (&S)[N], const T &Value) {
-    assert(N);
-    if (!Result && Str.size() >= N-1 &&
-        (N == 1 || std::memcmp(S, Str.data() + Str.size() + 1 - N, N-1) == 0)) {
-      Result = &Value;
+  StringSwitch& EndsWith(StringLiteral S, T Value) {
+    if (!Result && Str.endswith(S)) {
+      Result = std::move(Value);
     }
     return *this;
   }
 
-  template<unsigned N>
   LLVM_ATTRIBUTE_ALWAYS_INLINE
-  StringSwitch& StartsWith(const char (&S)[N], const T &Value) {
-    assert(N);
-    if (!Result && Str.size() >= N-1 &&
-        (N == 1 || std::memcmp(S, Str.data(), N-1) == 0)) {
-      Result = &Value;
+  StringSwitch& StartsWith(StringLiteral S, T Value) {
+    if (!Result && Str.startswith(S)) {
+      Result = std::move(Value);
     }
     return *this;
   }
 
-  template<unsigned N0, unsigned N1>
   LLVM_ATTRIBUTE_ALWAYS_INLINE
-  StringSwitch &Cases(const char (&S0)[N0], const char (&S1)[N1],
-                      const T& Value) {
+  StringSwitch &Cases(StringLiteral S0, StringLiteral S1, T Value) {
     return Case(S0, Value).Case(S1, Value);
   }
 
-  template<unsigned N0, unsigned N1, unsigned N2>
   LLVM_ATTRIBUTE_ALWAYS_INLINE
-  StringSwitch &Cases(const char (&S0)[N0], const char (&S1)[N1],
-                      const char (&S2)[N2], const T& Value) {
+  StringSwitch &Cases(StringLiteral S0, StringLiteral S1, StringLiteral S2,
+                      T Value) {
     return Case(S0, Value).Cases(S1, S2, Value);
   }
 
-  template<unsigned N0, unsigned N1, unsigned N2, unsigned N3>
   LLVM_ATTRIBUTE_ALWAYS_INLINE
-  StringSwitch &Cases(const char (&S0)[N0], const char (&S1)[N1],
-                      const char (&S2)[N2], const char (&S3)[N3],
-                      const T& Value) {
+  StringSwitch &Cases(StringLiteral S0, StringLiteral S1, StringLiteral S2,
+                      StringLiteral S3, T Value) {
     return Case(S0, Value).Cases(S1, S2, S3, Value);
   }
 
-  template<unsigned N0, unsigned N1, unsigned N2, unsigned N3, unsigned N4>
   LLVM_ATTRIBUTE_ALWAYS_INLINE
-  StringSwitch &Cases(const char (&S0)[N0], const char (&S1)[N1],
-                      const char (&S2)[N2], const char (&S3)[N3],
-                      const char (&S4)[N4], const T& Value) {
+  StringSwitch &Cases(StringLiteral S0, StringLiteral S1, StringLiteral S2,
+                      StringLiteral S3, StringLiteral S4, T Value) {
     return Case(S0, Value).Cases(S1, S2, S3, S4, Value);
   }
 
-  template <unsigned N0, unsigned N1, unsigned N2, unsigned N3, unsigned N4,
-            unsigned N5>
   LLVM_ATTRIBUTE_ALWAYS_INLINE
-  StringSwitch &Cases(const char (&S0)[N0], const char (&S1)[N1],
-                      const char (&S2)[N2], const char (&S3)[N3],
-                      const char (&S4)[N4], const char (&S5)[N5],
-                      const T &Value) {
+  StringSwitch &Cases(StringLiteral S0, StringLiteral S1, StringLiteral S2,
+                      StringLiteral S3, StringLiteral S4, StringLiteral S5,
+                      T Value) {
     return Case(S0, Value).Cases(S1, S2, S3, S4, S5, Value);
   }
 
-  template <unsigned N0, unsigned N1, unsigned N2, unsigned N3, unsigned N4,
-            unsigned N5, unsigned N6>
   LLVM_ATTRIBUTE_ALWAYS_INLINE
-  StringSwitch &Cases(const char (&S0)[N0], const char (&S1)[N1],
-                      const char (&S2)[N2], const char (&S3)[N3],
-                      const char (&S4)[N4], const char (&S5)[N5],
-                      const char (&S6)[N6], const T &Value) {
+  StringSwitch &Cases(StringLiteral S0, StringLiteral S1, StringLiteral S2,
+                      StringLiteral S3, StringLiteral S4, StringLiteral S5,
+                      StringLiteral S6, T Value) {
     return Case(S0, Value).Cases(S1, S2, S3, S4, S5, S6, Value);
   }
 
-  template <unsigned N0, unsigned N1, unsigned N2, unsigned N3, unsigned N4,
-            unsigned N5, unsigned N6, unsigned N7>
   LLVM_ATTRIBUTE_ALWAYS_INLINE
-  StringSwitch &Cases(const char (&S0)[N0], const char (&S1)[N1],
-                      const char (&S2)[N2], const char (&S3)[N3],
-                      const char (&S4)[N4], const char (&S5)[N5],
-                      const char (&S6)[N6], const char (&S7)[N7],
-                      const T &Value) {
+  StringSwitch &Cases(StringLiteral S0, StringLiteral S1, StringLiteral S2,
+                      StringLiteral S3, StringLiteral S4, StringLiteral S5,
+                      StringLiteral S6, StringLiteral S7, T Value) {
     return Case(S0, Value).Cases(S1, S2, S3, S4, S5, S6, S7, Value);
   }
 
-  template <unsigned N0, unsigned N1, unsigned N2, unsigned N3, unsigned N4,
-            unsigned N5, unsigned N6, unsigned N7, unsigned N8>
   LLVM_ATTRIBUTE_ALWAYS_INLINE
-  StringSwitch &Cases(const char (&S0)[N0], const char (&S1)[N1],
-                      const char (&S2)[N2], const char (&S3)[N3],
-                      const char (&S4)[N4], const char (&S5)[N5],
-                      const char (&S6)[N6], const char (&S7)[N7],
-                      const char (&S8)[N8], const T &Value) {
+  StringSwitch &Cases(StringLiteral S0, StringLiteral S1, StringLiteral S2,
+                      StringLiteral S3, StringLiteral S4, StringLiteral S5,
+                      StringLiteral S6, StringLiteral S7, StringLiteral S8,
+                      T Value) {
     return Case(S0, Value).Cases(S1, S2, S3, S4, S5, S6, S7, S8, Value);
   }
 
-  template <unsigned N0, unsigned N1, unsigned N2, unsigned N3, unsigned N4,
-            unsigned N5, unsigned N6, unsigned N7, unsigned N8, unsigned N9>
   LLVM_ATTRIBUTE_ALWAYS_INLINE
-  StringSwitch &Cases(const char (&S0)[N0], const char (&S1)[N1],
-                      const char (&S2)[N2], const char (&S3)[N3],
-                      const char (&S4)[N4], const char (&S5)[N5],
-                      const char (&S6)[N6], const char (&S7)[N7],
-                      const char (&S8)[N8], const char (&S9)[N9],
-                      const T &Value) {
+  StringSwitch &Cases(StringLiteral S0, StringLiteral S1, StringLiteral S2,
+                      StringLiteral S3, StringLiteral S4, StringLiteral S5,
+                      StringLiteral S6, StringLiteral S7, StringLiteral S8,
+                      StringLiteral S9, T Value) {
     return Case(S0, Value).Cases(S1, S2, S3, S4, S5, S6, S7, S8, S9, Value);
   }
 
   // Case-insensitive case matchers.
-  template <unsigned N>
-  LLVM_ATTRIBUTE_ALWAYS_INLINE StringSwitch &CaseLower(const char (&S)[N],
-                                                       const T &Value) {
-    if (!Result && Str.equals_lower(StringRef(S, N - 1)))
-      Result = &Value;
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
+  StringSwitch &CaseLower(StringLiteral S, T Value) {
+    if (!Result && Str.equals_lower(S))
+      Result = std::move(Value);
 
     return *this;
   }
 
-  template <unsigned N>
-  LLVM_ATTRIBUTE_ALWAYS_INLINE StringSwitch &EndsWithLower(const char (&S)[N],
-                                                           const T &Value) {
-    if (!Result && Str.endswith_lower(StringRef(S, N - 1)))
-      Result = &Value;
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
+  StringSwitch &EndsWithLower(StringLiteral S, T Value) {
+    if (!Result && Str.endswith_lower(S))
+      Result = Value;
 
     return *this;
   }
 
-  template <unsigned N>
-  LLVM_ATTRIBUTE_ALWAYS_INLINE StringSwitch &StartsWithLower(const char (&S)[N],
-                                                             const T &Value) {
-    if (!Result && Str.startswith_lower(StringRef(S, N - 1)))
-      Result = &Value;
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
+  StringSwitch &StartsWithLower(StringLiteral S, T Value) {
+    if (!Result && Str.startswith_lower(S))
+      Result = std::move(Value);
 
     return *this;
   }
-  template <unsigned N0, unsigned N1>
-  LLVM_ATTRIBUTE_ALWAYS_INLINE StringSwitch &
-  CasesLower(const char (&S0)[N0], const char (&S1)[N1], const T &Value) {
+
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
+  StringSwitch &CasesLower(StringLiteral S0, StringLiteral S1, T Value) {
     return CaseLower(S0, Value).CaseLower(S1, Value);
   }
 
-  template <unsigned N0, unsigned N1, unsigned N2>
-  LLVM_ATTRIBUTE_ALWAYS_INLINE StringSwitch &
-  CasesLower(const char (&S0)[N0], const char (&S1)[N1], const char (&S2)[N2],
-             const T &Value) {
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
+  StringSwitch &CasesLower(StringLiteral S0, StringLiteral S1, StringLiteral S2,
+                           T Value) {
     return CaseLower(S0, Value).CasesLower(S1, S2, Value);
   }
 
-  template <unsigned N0, unsigned N1, unsigned N2, unsigned N3>
-  LLVM_ATTRIBUTE_ALWAYS_INLINE StringSwitch &
-  CasesLower(const char (&S0)[N0], const char (&S1)[N1], const char (&S2)[N2],
-             const char (&S3)[N3], const T &Value) {
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
+  StringSwitch &CasesLower(StringLiteral S0, StringLiteral S1, StringLiteral S2,
+                           StringLiteral S3, T Value) {
     return CaseLower(S0, Value).CasesLower(S1, S2, S3, Value);
   }
 
-  template <unsigned N0, unsigned N1, unsigned N2, unsigned N3, unsigned N4>
-  LLVM_ATTRIBUTE_ALWAYS_INLINE StringSwitch &
-  CasesLower(const char (&S0)[N0], const char (&S1)[N1], const char (&S2)[N2],
-             const char (&S3)[N3], const char (&S4)[N4], const T &Value) {
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
+  StringSwitch &CasesLower(StringLiteral S0, StringLiteral S1, StringLiteral S2,
+                           StringLiteral S3, StringLiteral S4, T Value) {
     return CaseLower(S0, Value).CasesLower(S1, S2, S3, S4, Value);
   }
 
+  LLVM_NODISCARD
   LLVM_ATTRIBUTE_ALWAYS_INLINE
-  R Default(const T &Value) const {
+  R Default(T Value) {
     if (Result)
-      return *Result;
+      return std::move(*Result);
     return Value;
   }
 
+  LLVM_NODISCARD
   LLVM_ATTRIBUTE_ALWAYS_INLINE
-  operator R() const {
+  operator R() {
     assert(Result && "Fell off the end of a string-switch");
-    return *Result;
+    return std::move(*Result);
   }
 };
 
diff --git a/llvm/unittests/ADT/StringSwitchTest.cpp b/llvm/unittests/ADT/StringSwitchTest.cpp
index 1a51629ca57..62d3a319e7a 100644
--- a/llvm/unittests/ADT/StringSwitchTest.cpp
+++ b/llvm/unittests/ADT/StringSwitchTest.cpp
@@ -158,7 +158,8 @@ TEST(StringSwitchTest, Cases) {
 
   auto Translate = [](StringRef S) {
     return llvm::StringSwitch<OSType>(S)
-        .Cases("wind\0ws", "win32", "winnt", OSType::Windows)
+        .Cases(StringLiteral::withInnerNUL("wind\0ws"), "win32", "winnt",
+               OSType::Windows)
         .Cases("linux", "unix", "*nix", "posix", OSType::Linux)
         .Default(OSType::Unknown);
   };
@@ -184,7 +185,8 @@ TEST(StringSwitchTest, CasesLower) {
 
   auto Translate = [](StringRef S) {
     return llvm::StringSwitch<OSType>(S)
-        .CasesLower("wind\0ws", "win32", "winnt", OSType::Windows)
+        .CasesLower(StringLiteral::withInnerNUL("wind\0ws"), "win32", "winnt",
+                    OSType::Windows)
         .CasesLower("linux", "unix", "*nix", "posix", OSType::Linux)
         .Default(OSType::Unknown);
   };