https://bugs.llvm.org/show_bug.cgi?id=33840
Bug ID: 33840
Summary: std::string::push_back is 3.4x slower than on
libstdc++
Product: libc++
Version: unspecified
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: All Bugs
Assignee: unassignedclangb...@nondot.org
Reporter: thomasander...@google.com
CC: llvm-bugs@lists.llvm.org, mclow.li...@gmail.com
Simple program that demonstrates the issue:
----test.cpp----
#include <string>
int main(void) {
std::string s;
for(volatile int i = 0; i < 500000000; i++) {
s.push_back('a');
}
return 0;
}
----test.cpp----
$ clang++ main.cpp -stdlib=libstdc++ && time ./a.out
real 0m2.451s
$ clang++ main.cpp -stdlib=libc++ && time ./a.out
real 0m8.535s
I've verified that it is always a constant factor of 3.4x slower than libstdc++
regardless of the input size.
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