Optimize demangling
Don't continually replace the string in-place.
Makes pathological fuzzer tests ~140x faster to run.
Fixed: chromium:1182606
Change-Id: I48bd39ecb8488e34c9e75da52b5e9f355ca896ee
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/43920
Commit-Queue: Ben Clayton <bclayton@google.com>
Auto-Submit: Ben Clayton <bclayton@google.com>
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
diff --git a/src/demangler.cc b/src/demangler.cc
index 54d316e..a85f9bd 100644
--- a/src/demangler.cc
+++ b/src/demangler.cc
@@ -14,6 +14,8 @@
#include "src/demangler.h"
+#include <sstream>
+
#include "src/ast/module.h"
#include "src/program.h"
@@ -31,31 +33,33 @@
std::string Demangler::Demangle(const SymbolTable& symbols,
const std::string& str) const {
- auto ret = str;
+ std::stringstream out;
size_t pos = 0;
for (;;) {
- auto idx = ret.find(kSymbol, pos);
- if (idx == std::string::npos)
+ auto idx = str.find(kSymbol, pos);
+ if (idx == std::string::npos) {
+ out << str.substr(pos);
break;
+ }
+
+ out << str.substr(pos, idx - pos);
auto start_idx = idx + kSymbolLen;
auto end_idx = start_idx;
- while (ret[end_idx] >= '0' && ret[end_idx] <= '9') {
+ while (str[end_idx] >= '0' && str[end_idx] <= '9') {
end_idx++;
}
auto len = end_idx - start_idx;
- auto id = ret.substr(start_idx, len);
-
+ auto id = str.substr(start_idx, len);
Symbol sym(std::stoi(id));
- auto name = symbols.NameFor(sym);
- ret.replace(idx, end_idx - idx, name);
+ out << symbols.NameFor(sym);
- pos = idx + name.length();
+ pos = end_idx;
}
- return ret;
+ return out.str();
}
} // namespace tint
