[ADT] Micro-optimize and force inlining for string switches.

These are now quite heavily used in unit tests and the host tools,
making it worth having them be reasonably fast even in an unoptimized
build. This change reduces the total runtime of TripleTest.Normalization
by yet another 10% to 15%. It is now under 10 seconds on my machine, and
the total check-llvm time has dropped from 38s to around 36s.

I experimented with a number of different options, and the code pattern
here consistently seemed to lower the cleanest, likely due to the
significantly simple CFG and far fewer redundant tests of 'Result'.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247257 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/ADT/StringSwitch.h b/include/llvm/ADT/StringSwitch.h
index 0393a0c373efc5f2becc640cef6b01c4bf368184..42b0fc4bc441f68b2d55e0b70e4e63b6fec0fb29 100644 (file)
--- a/include/llvm/ADT/StringSwitch.h
+++ b/include/llvm/ADT/StringSwitch.h
@@ -14,6 +14,7 @@
 #define LLVM_ADT_STRINGSWITCH_H
 
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Compiler.h"
 #include <cassert>
 #include <cstring>
 
@@ -48,10 +49,12 @@ class StringSwitch {
   const T *Result;
 
 public:
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
   explicit StringSwitch(StringRef S)
   : Str(S), Result(nullptr) { }
 
   template<unsigned N>
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
   StringSwitch& Case(const char (&S)[N], const T& Value) {
     if (!Result && N-1 == Str.size() &&
         (std::memcmp(S, Str.data(), N-1) == 0)) {
@@ -62,6 +65,7 @@ public:
   }
 
   template<unsigned N>
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
   StringSwitch& EndsWith(const char (&S)[N], const T &Value) {
     if (!Result && Str.size() >= N-1 &&
         std::memcmp(S, Str.data() + Str.size() + 1 - N, N-1) == 0) {
@@ -72,6 +76,7 @@ public:
   }
 
   template<unsigned N>
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
   StringSwitch& StartsWith(const char (&S)[N], const T &Value) {
     if (!Result && Str.size() >= N-1 &&
         std::memcmp(S, Str.data(), N-1) == 0) {
@@ -82,32 +87,66 @@ public:
   }
 
   template<unsigned N0, unsigned N1>
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
   StringSwitch& Cases(const char (&S0)[N0], const char (&S1)[N1],
                       const T& Value) {
-    return Case(S0, Value).Case(S1, Value);
+    if (!Result && (
+        (N0-1 == Str.size() && std::memcmp(S0, Str.data(), N0-1) == 0) ||
+        (N1-1 == Str.size() && std::memcmp(S1, Str.data(), N1-1) == 0))) {
+      Result = &Value;
+    }
+
+    return *this;
   }
 
   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) {
-    return Case(S0, Value).Case(S1, Value).Case(S2, Value);
+    if (!Result && (
+        (N0-1 == Str.size() && std::memcmp(S0, Str.data(), N0-1) == 0) ||
+        (N1-1 == Str.size() && std::memcmp(S1, Str.data(), N1-1) == 0) ||
+        (N2-1 == Str.size() && std::memcmp(S2, Str.data(), N2-1) == 0))) {
+      Result = &Value;
+    }
+
+    return *this;
   }
 
   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) {
-    return Case(S0, Value).Case(S1, Value).Case(S2, Value).Case(S3, Value);
+    if (!Result && (
+        (N0-1 == Str.size() && std::memcmp(S0, Str.data(), N0-1) == 0) ||
+        (N1-1 == Str.size() && std::memcmp(S1, Str.data(), N1-1) == 0) ||
+        (N2-1 == Str.size() && std::memcmp(S2, Str.data(), N2-1) == 0) ||
+        (N3-1 == Str.size() && std::memcmp(S3, Str.data(), N3-1) == 0))) {
+      Result = &Value;
+    }
+
+    return *this;
   }
 
   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) {
-    return Case(S0, Value).Case(S1, Value).Case(S2, Value).Case(S3, Value)
-      .Case(S4, Value);
+    if (!Result && (
+        (N0-1 == Str.size() && std::memcmp(S0, Str.data(), N0-1) == 0) ||
+        (N1-1 == Str.size() && std::memcmp(S1, Str.data(), N1-1) == 0) ||
+        (N2-1 == Str.size() && std::memcmp(S2, Str.data(), N2-1) == 0) ||
+        (N3-1 == Str.size() && std::memcmp(S3, Str.data(), N3-1) == 0) ||
+        (N4-1 == Str.size() && std::memcmp(S4, Str.data(), N4-1) == 0))) {
+      Result = &Value;
+    }
+
+    return *this;
   }
 
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
   R Default(const T& Value) const {
     if (Result)
       return *Result;
@@ -115,6 +154,7 @@ public:
     return Value;
   }
 
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
   operator R() const {
     assert(Result && "Fell off the end of a string-switch");
     return *Result;