From 75cffdf92c691b428eb58c67c86baa32c938f6a7 Mon Sep 17 00:00:00 2001
From: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Date: Mon, 5 Feb 2018 16:07:39 -0800
Subject: [PATCH] Preprocessor: Use std::string instead of std::stringstream
std::stringstream has a measurable overhead for preprocessing - it
appears that operator<< does a tiny bit of extra work for appending
chars/strings and also can't be inlined in most cases on VS2015;
additionally, std::endl triggers a stream flush which also adds up.
Replacing this with std::string buffer gets the preprocessing time down
from 180ms to 135ms in one case, making it 1.33x faster.
Note that integer-to-string conversion is using std::to_string; in
theory this could be slower than sprintf or manual conversion, but I
haven't found these cases to affect preprocessing time in practice
(std::to_string would always use the short string buffer for
line/version numbers, and the number of calls is not too significant).
---
glslang/MachineIndependent/ShaderLang.cpp | 65 +++++++++++++----------
1 file changed, 37 insertions(+), 28 deletions(-)
diff --git a/glslang/MachineIndependent/ShaderLang.cpp b/glslang/MachineIndependent/ShaderLang.cpp
index c92d02391..21004fede 100644
--- a/glslang/MachineIndependent/ShaderLang.cpp
+++ b/glslang/MachineIndependent/ShaderLang.cpp
@@ -912,7 +912,7 @@ bool ProcessDeferred(
class SourceLineSynchronizer {
public:
SourceLineSynchronizer(const std::function<int()>& lastSourceIndex,
- std::stringstream* output)
+ std::string* output)
: getLastSourceIndex(lastSourceIndex), output(output), lastSource(-1), lastLine(0) {}
// SourceLineSynchronizer(const SourceLineSynchronizer&) = delete;
// SourceLineSynchronizer& operator=(const SourceLineSynchronizer&) = delete;
@@ -927,7 +927,7 @@ public:
// used. We also need to output a newline to separate the output
// from the previous source string (if there is one).
if (lastSource != -1 || lastLine != 0)
- *output << std::endl;
+ *output += '\n';
lastSource = getLastSourceIndex();
lastLine = -1;
return true;
@@ -942,7 +942,7 @@ public:
syncToMostRecentString();
const bool newLineStarted = lastLine < tokenLine;
for (; lastLine < tokenLine; ++lastLine) {
- if (lastLine > 0) *output << std::endl;
+ if (lastLine > 0) *output += '\n';
}
return newLineStarted;
}
@@ -956,8 +956,8 @@ private:
// A function for getting the index of the last valid source string we've
// read tokens from.
const std::function<int()> getLastSourceIndex;
- // output stream for newlines.
- std::stringstream* output;
+ // output string for newlines.
+ std::string* output;
// lastSource is the source string index (starting from 0) of the last token
// processed. It is tracked in order for newlines to be inserted when a new
// source string starts. -1 means we haven't started processing any source
@@ -988,27 +988,33 @@ struct DoPreprocessing {
parseContext.setScanner(&input);
ppContext.setInput(input, versionWillBeError);
- std::stringstream outputStream;
+ std::string outputBuffer;
SourceLineSynchronizer lineSync(
- std::bind(&TInputScanner::getLastValidSourceIndex, &input), &outputStream);
+ std::bind(&TInputScanner::getLastValidSourceIndex, &input), &outputBuffer);
- parseContext.setExtensionCallback([&lineSync, &outputStream](
+ parseContext.setExtensionCallback([&lineSync, &outputBuffer](
int line, const char* extension, const char* behavior) {
lineSync.syncToLine(line);
- outputStream << "#extension " << extension << " : " << behavior;
+ outputBuffer += "#extension ";
+ outputBuffer += extension;
+ outputBuffer += " : ";
+ outputBuffer += behavior;
});
- parseContext.setLineCallback([&lineSync, &outputStream, &parseContext](
+ parseContext.setLineCallback([&lineSync, &outputBuffer, &parseContext](
int curLineNum, int newLineNum, bool hasSource, int sourceNum, const char* sourceName) {
// SourceNum is the number of the source-string that is being parsed.
lineSync.syncToLine(curLineNum);
- outputStream << "#line " << newLineNum;
+ outputBuffer += "#line ";
+ outputBuffer += std::to_string(newLineNum);
if (hasSource) {
- outputStream << " ";
+ outputBuffer += ' ';
if (sourceName != nullptr) {
- outputStream << "\"" << sourceName << "\"";
+ outputBuffer += '\"';
+ outputBuffer += sourceName;
+ outputBuffer += '\"';
} else {
- outputStream << sourceNum;
+ outputBuffer += std::to_string(sourceNum);
}
}
if (parseContext.lineDirectiveShouldSetNextLine()) {
@@ -1016,33 +1022,36 @@ struct DoPreprocessing {
// directive. So the new line number for the current line is
newLineNum -= 1;
}
- outputStream << std::endl;
+ outputBuffer += '\n';
// And we are at the next line of the #line directive now.
lineSync.setLineNum(newLineNum + 1);
});
parseContext.setVersionCallback(
- [&lineSync, &outputStream](int line, int version, const char* str) {
+ [&lineSync, &outputBuffer](int line, int version, const char* str) {
lineSync.syncToLine(line);
- outputStream << "#version " << version;
+ outputBuffer += "#version ";
+ outputBuffer += std::to_string(version);
if (str) {
- outputStream << " " << str;
+ outputBuffer += ' ';
+ outputBuffer += str;
}
});
- parseContext.setPragmaCallback([&lineSync, &outputStream](
+ parseContext.setPragmaCallback([&lineSync, &outputBuffer](
int line, const glslang::TVector<glslang::TString>& ops) {
lineSync.syncToLine(line);
- outputStream << "#pragma ";
+ outputBuffer += "#pragma ";
for(size_t i = 0; i < ops.size(); ++i) {
- outputStream << ops[i];
+ outputBuffer += ops[i].c_str();
}
});
- parseContext.setErrorCallback([&lineSync, &outputStream](
+ parseContext.setErrorCallback([&lineSync, &outputBuffer](
int line, const char* errorMessage) {
lineSync.syncToLine(line);
- outputStream << "#error " << errorMessage;
+ outputBuffer += "#error ";
+ outputBuffer += errorMessage;
});
int lastToken = EndOfInput; // lastToken records the last token processed.
@@ -1058,7 +1067,7 @@ struct DoPreprocessing {
// Don't emit whitespace onto empty lines.
// Copy any whitespace characters at the start of a line
// from the input to the output.
- outputStream << std::string(ppToken.loc.column - 1, ' ');
+ outputBuffer += std::string(ppToken.loc.column - 1, ' ');
}
// Output a space in between tokens, but not at the start of a line,
@@ -1068,13 +1077,13 @@ struct DoPreprocessing {
(unNeededSpaceTokens.find((char)token) == std::string::npos) &&
(unNeededSpaceTokens.find((char)lastToken) == std::string::npos) &&
(noSpaceBeforeTokens.find((char)token) == std::string::npos)) {
- outputStream << " ";
+ outputBuffer += ' ';
}
lastToken = token;
- outputStream << ppToken.name;
+ outputBuffer += ppToken.name;
} while (true);
- outputStream << std::endl;
- *outputString = outputStream.str();
+ outputBuffer += '\n';
+ *outputString = std::move(outputBuffer);
bool success = true;
if (parseContext.getNumErrors() > 0) {
--
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