[llvm] r247253 - [ADT] Apply a large hammer to StringRef functions: attribute always_inline.
Justin Bogner via llvm-commits
llvm-commits at lists.llvm.org
Tue Sep 15 20:16:40 PDT 2015
Chandler Carruth via llvm-commits <llvm-commits at lists.llvm.org> writes:
> Author: chandlerc
> Date: Thu Sep 10 03:29:35 2015
> New Revision: 247253
>
> URL: http://llvm.org/viewvc/llvm-project?rev=247253&view=rev
> Log:
> [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.
>
> Modified:
> llvm/trunk/include/llvm/ADT/StringRef.h
>
> Modified: llvm/trunk/include/llvm/ADT/StringRef.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/StringRef.h?rev=247253&r1=247252&r2=247253&view=diff
> ==============================================================================
>
> --- llvm/trunk/include/llvm/ADT/StringRef.h (original)
> +++ llvm/trunk/include/llvm/ADT/StringRef.h Thu Sep 10 03:29:35 2015
> @@ -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()) {}
This makes constructing StringRefs in lldb basically impossible, which
means that functions in llvm that take a string for an argument are
basically uncallable in a debugger. So, basically, this makes my life
much worse. I'm fine with making "-O0 -g" builds faster if there isn't
really a cost to it, but this kind of thing is just a work around for
the fact that nobody's bothering to invest in making optimized debugging
in llvm useable. The trade off is wrong.
>
> @@ -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);
> }
>
>
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