[ADT] Apply a large hammer to StringRef functions: attribute always_inline.

The logic of this follows something Howard does in libc++ and something
I discussed with Chris eons ago -- for a lot of functions, there is
really no benefit to preserving "debug information" by leaving the
out-of-line even in debug builds. This is especially true as we now do
a very good job of preserving most debug information even in the face of
inlining. There are a bunch of methods in StringRef that we are paying
a completely unacceptable amount for with every debug build of every
LLVM developer.

Some day, we should fix Clang/LLVM so that developers can reasonable
use a default of something other than '-O0' and not waste their lives
waiting on *completely* unoptimized code to execute. We should have
a default that doesn't impede debugging while providing at least
plausable performance.

But today is not that day.

So today, I'm applying always_inline to the functions that are really
hurting the critical path for stuff like 'check_llvm'. I'm being very
cautious here, but there are a few other APIs that we really should do
this for as a matter of pragmatism. Hopefully we can rip this out some
day.

With this change, TripleTest.Normalization runtime decreases by over
10%, and the total 'check-llvm' time on my 48-core box goes from 38s to
just under 37s.

llvm-svn: 247253

include/llvm/ADT/StringRef.h

@@ -10,6 +10,7 @@
 #ifndef LLVM_ADT_STRINGREF_H
 #define LLVM_ADT_STRINGREF_H
 
+#include "llvm/Support/Compiler.h"
 #include <algorithm>
 #include <cassert>
 #include <cstring>
@@ -53,6 +54,7 @@ namespace llvm {
 
     // Workaround memcmp issue with null pointers (undefined behavior)
     // by providing a specialized version
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     static int compareMemory(const char *Lhs, const char *Rhs, size_t Length) {
       if (Length == 0) { return 0; }
       return ::memcmp(Lhs,Rhs,Length);
@@ -63,9 +65,11 @@ namespace llvm {
     /// @{
 
     /// Construct an empty string ref.
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     /*implicit*/ StringRef() : Data(nullptr), Length(0) {}
 
     /// Construct a string ref from a cstring.
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     /*implicit*/ StringRef(const char *Str)
       : Data(Str) {
         assert(Str && "StringRef cannot be built from a NULL argument");
@@ -73,6 +77,7 @@ namespace llvm {
       }
 
     /// Construct a string ref from a pointer and length.
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     /*implicit*/ StringRef(const char *data, size_t length)
       : Data(data), Length(length) {
         assert((data || length == 0) &&
@@ -80,6 +85,7 @@ namespace llvm {
       }
 
     /// Construct a string ref from an std::string.
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     /*implicit*/ StringRef(const std::string &Str)
       : Data(Str.data()), Length(Str.length()) {}
 
@@ -104,12 +110,15 @@ namespace llvm {
 
     /// data - Get a pointer to the start of the string (which may not be null
     /// terminated).
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     const char *data() const { return Data; }
 
     /// empty - Check if the string is empty.
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     bool empty() const { return Length == 0; }
 
     /// size - Get the string size.
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     size_t size() const { return Length; }
 
     /// front - Get the first character in the string.
@@ -133,6 +142,7 @@ namespace llvm {
 
     /// equals - Check for string equality, this is more efficient than
     /// compare() when the relative ordering of inequal strings isn't needed.
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     bool equals(StringRef RHS) const {
       return (Length == RHS.Length &&
               compareMemory(Data, RHS.Data, RHS.Length) == 0);
@@ -145,6 +155,7 @@ namespace llvm {
 
     /// compare - Compare two strings; the result is -1, 0, or 1 if this string
     /// is lexicographically less than, equal to, or greater than the \p RHS.
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     int compare(StringRef RHS) const {
       // Check the prefix for a mismatch.
       if (int Res = compareMemory(Data, RHS.Data, std::min(Length, RHS.Length)))
@@ -212,6 +223,7 @@ namespace llvm {
     /// @{
 
     /// Check if this string starts with the given \p Prefix.
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     bool startswith(StringRef Prefix) const {
       return Length >= Prefix.Length &&
              compareMemory(Data, Prefix.Data, Prefix.Length) == 0;
@@ -221,6 +233,7 @@ namespace llvm {
     bool startswith_lower(StringRef Prefix) const;
 
     /// Check if this string ends with the given \p Suffix.
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     bool endswith(StringRef Suffix) const {
       return Length >= Suffix.Length &&
         compareMemory(end() - Suffix.Length, Suffix.Data, Suffix.Length) == 0;
@@ -237,6 +250,7 @@ namespace llvm {
     ///
     /// \returns The index of the first occurrence of \p C, or npos if not
     /// found.
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     size_t find(char C, size_t From = 0) const {
       size_t FindBegin = std::min(From, Length);
       if (FindBegin < Length) { // Avoid calling memchr with nullptr.
@@ -402,6 +416,7 @@ namespace llvm {
     /// \param N The number of characters to included in the substring. If N
     /// exceeds the number of characters remaining in the string, the string
     /// suffix (starting with \p Start) will be returned.
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     StringRef substr(size_t Start, size_t N = npos) const {
       Start = std::min(Start, Length);
       return StringRef(Data + Start, std::min(N, Length - Start));
@@ -409,6 +424,7 @@ namespace llvm {
 
     /// Return a StringRef equal to 'this' but with the first \p N elements
     /// dropped.
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     StringRef drop_front(size_t N = 1) const {
       assert(size() >= N && "Dropping more elements than exist");
       return substr(N);
@@ -416,6 +432,7 @@ namespace llvm {
 
     /// Return a StringRef equal to 'this' but with the last \p N elements
     /// dropped.
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     StringRef drop_back(size_t N = 1) const {
       assert(size() >= N && "Dropping more elements than exist");
       return substr(0, size()-N);
@@ -431,6 +448,7 @@ namespace llvm {
     /// substring. If this is npos, or less than \p Start, or exceeds the
     /// number of characters remaining in the string, the string suffix
     /// (starting with \p Start) will be returned.
+    LLVM_ATTRIBUTE_ALWAYS_INLINE
     StringRef slice(size_t Start, size_t End) const {
       Start = std::min(Start, Length);
       End = std::min(std::max(Start, End), Length);
@@ -547,10 +565,12 @@ namespace llvm {
   /// @name StringRef Comparison Operators
   /// @{
 
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
   inline bool operator==(StringRef LHS, StringRef RHS) {
     return LHS.equals(RHS);
   }
 
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
   inline bool operator!=(StringRef LHS, StringRef RHS) {
     return !(LHS == RHS);
   }