From 61cac1fabb3953830995eefe6a1cca4573033685 Mon Sep 17 00:00:00 2001
From: Andy Getzendanner <durandal@google.com>
Date: Mon, 1 May 2023 14:07:31 -0700
Subject: Instantiate LogMessage::CopyToEncodedBuffer separately for literals
 and non-literals to save an instruction at each operator<<(string) callsite.

The operator<<s get inlined at the callsite.  The saved instruction is a 'load immediate' to put the StringType argument in a register for passing.

This does make the logging TU slightly larger, but it will be an overall size win for all but the smallest programs.  Smaller, faster code at callsites is worth it anyway.

PiperOrigin-RevId: 528569773
Change-Id: Id8185266a975a12ab6f1a553c2c0846261822396
---
 absl/log/internal/log_message.cc | 19 ++++++++++++++-----
 absl/log/internal/log_message.h  | 28 +++++++++++++++++++---------
 absl/log/internal/structured.h   |  2 +-
 3 files changed, 34 insertions(+), 15 deletions(-)

(limited to 'absl/log')

diff --git a/absl/log/internal/log_message.cc b/absl/log/internal/log_message.cc
index 4deca722..10ac2453 100644
--- a/absl/log/internal/log_message.cc
+++ b/absl/log/internal/log_message.cc
@@ -353,12 +353,12 @@ void LogMessage::FailQuietly() {
 }
 
 LogMessage& LogMessage::operator<<(const std::string& v) {
-  CopyToEncodedBuffer(v, StringType::kNotLiteral);
+  CopyToEncodedBuffer<StringType::kNotLiteral>(v);
   return *this;
 }
 
 LogMessage& LogMessage::operator<<(absl::string_view v) {
-  CopyToEncodedBuffer(v, StringType::kNotLiteral);
+  CopyToEncodedBuffer<StringType::kNotLiteral>(v);
   return *this;
 }
 LogMessage& LogMessage::operator<<(std::ostream& (*m)(std::ostream& os)) {
@@ -525,8 +525,8 @@ void LogMessage::LogBacktraceIfNeeded() {
 // containing the specified string data using a `Value` field appropriate to
 // `str_type`.  Truncates `str` if necessary, but emits nothing and marks the
 // buffer full if  even the field headers do not fit.
-void LogMessage::CopyToEncodedBuffer(absl::string_view str,
-                                     StringType str_type) {
+template <LogMessage::StringType str_type>
+void LogMessage::CopyToEncodedBuffer(absl::string_view str) {
   auto encoded_remaining_copy = data_->encoded_remaining;
   auto start = EncodeMessageStart(
       EventTag::kValue, BufferSizeFor(WireType::kLengthDelimited) + str.size(),
@@ -547,7 +547,12 @@ void LogMessage::CopyToEncodedBuffer(absl::string_view str,
     data_->encoded_remaining.remove_suffix(data_->encoded_remaining.size());
   }
 }
-void LogMessage::CopyToEncodedBuffer(char ch, size_t num, StringType str_type) {
+template void LogMessage::CopyToEncodedBuffer<LogMessage::StringType::kLiteral>(
+    absl::string_view str);
+template void LogMessage::CopyToEncodedBuffer<
+    LogMessage::StringType::kNotLiteral>(absl::string_view str);
+template <LogMessage::StringType str_type>
+void LogMessage::CopyToEncodedBuffer(char ch, size_t num) {
   auto encoded_remaining_copy = data_->encoded_remaining;
   auto value_start = EncodeMessageStart(
       EventTag::kValue, BufferSizeFor(WireType::kLengthDelimited) + num,
@@ -568,6 +573,10 @@ void LogMessage::CopyToEncodedBuffer(char ch, size_t num, StringType str_type) {
     data_->encoded_remaining.remove_suffix(data_->encoded_remaining.size());
   }
 }
+template void LogMessage::CopyToEncodedBuffer<LogMessage::StringType::kLiteral>(
+    char ch, size_t num);
+template void LogMessage::CopyToEncodedBuffer<
+    LogMessage::StringType::kNotLiteral>(char ch, size_t num);
 
 LogMessageFatal::LogMessageFatal(const char* file, int line)
     : LogMessage(file, line, absl::LogSeverity::kFatal) {}
diff --git a/absl/log/internal/log_message.h b/absl/log/internal/log_message.h
index 6fdfa7bd..46937728 100644
--- a/absl/log/internal/log_message.h
+++ b/absl/log/internal/log_message.h
@@ -231,10 +231,10 @@ class LogMessage {
     kLiteral,
     kNotLiteral,
   };
-  void CopyToEncodedBuffer(absl::string_view str,
-                           StringType str_type) ABSL_ATTRIBUTE_NOINLINE;
-  void CopyToEncodedBuffer(char ch, size_t num,
-                           StringType str_type) ABSL_ATTRIBUTE_NOINLINE;
+  template <StringType str_type>
+  void CopyToEncodedBuffer(absl::string_view str) ABSL_ATTRIBUTE_NOINLINE;
+  template <StringType str_type>
+  void CopyToEncodedBuffer(char ch, size_t num) ABSL_ATTRIBUTE_NOINLINE;
 
   // Returns `true` if the message is fatal or enabled debug-fatal.
   bool IsFatal() const;
@@ -264,12 +264,12 @@ class StringifySink final {
   explicit StringifySink(LogMessage& message) : message_(message) {}
 
   void Append(size_t count, char ch) {
-    message_.CopyToEncodedBuffer(ch, count,
-                                 LogMessage::StringType::kNotLiteral);
+    message_.CopyToEncodedBuffer<LogMessage::StringType::kNotLiteral>(ch,
+                                                                      count);
   }
 
   void Append(absl::string_view v) {
-    message_.CopyToEncodedBuffer(v, LogMessage::StringType::kNotLiteral);
+    message_.CopyToEncodedBuffer<LogMessage::StringType::kNotLiteral>(v);
   }
 
   // For types that implement `AbslStringify` using `absl::Format()`.
@@ -304,14 +304,14 @@ LogMessage& LogMessage::operator<<(const T& v) {
 
 template <int SIZE>
 LogMessage& LogMessage::operator<<(const char (&buf)[SIZE]) {
-  CopyToEncodedBuffer(buf, StringType::kLiteral);
+  CopyToEncodedBuffer<StringType::kLiteral>(buf);
   return *this;
 }
 
 // Note: the following is declared `ABSL_ATTRIBUTE_NOINLINE`
 template <int SIZE>
 LogMessage& LogMessage::operator<<(char (&buf)[SIZE]) {
-  CopyToEncodedBuffer(buf, StringType::kNotLiteral);
+  CopyToEncodedBuffer<StringType::kNotLiteral>(buf);
   return *this;
 }
 // We instantiate these specializations in the library's TU to save space in
@@ -339,6 +339,16 @@ extern template LogMessage& LogMessage::operator<<(const float& v);
 extern template LogMessage& LogMessage::operator<<(const double& v);
 extern template LogMessage& LogMessage::operator<<(const bool& v);
 
+extern template void LogMessage::CopyToEncodedBuffer<
+    LogMessage::StringType::kLiteral>(absl::string_view str);
+extern template void LogMessage::CopyToEncodedBuffer<
+    LogMessage::StringType::kNotLiteral>(absl::string_view str);
+extern template void
+LogMessage::CopyToEncodedBuffer<LogMessage::StringType::kLiteral>(char ch,
+                                                                  size_t num);
+extern template void LogMessage::CopyToEncodedBuffer<
+    LogMessage::StringType::kNotLiteral>(char ch, size_t num);
+
 // `LogMessageFatal` ensures the process will exit in failure after logging this
 // message.
 class LogMessageFatal final : public LogMessage {
diff --git a/absl/log/internal/structured.h b/absl/log/internal/structured.h
index 08caea66..5223dbc3 100644
--- a/absl/log/internal/structured.h
+++ b/absl/log/internal/structured.h
@@ -42,7 +42,7 @@ class ABSL_MUST_USE_RESULT AsLiteralImpl final {
     return os << as_literal.str_;
   }
   void AddToMessage(log_internal::LogMessage& m) {
-    m.CopyToEncodedBuffer(str_, log_internal::LogMessage::StringType::kLiteral);
+    m.CopyToEncodedBuffer<log_internal::LogMessage::StringType::kLiteral>(str_);
   }
   friend log_internal::LogMessage& operator<<(log_internal::LogMessage& m,
                                               AsLiteralImpl as_literal) {
-- 
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