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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>
This commit is contained in:
Ben Clayton 2021-03-04 16:29:05 +00:00 committed by Commit Bot service account
parent f76f3081af
commit 798876e7eb
1 changed files with 14 additions and 10 deletions
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24
src/demangler.cc
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@ -14,6 +14,8 @@
#include "src/demangler.h" #include "src/demangler.h"
#include <sstream>
#include "src/ast/module.h" #include "src/ast/module.h"
#include "src/program.h" #include "src/program.h"
@ -31,31 +33,33 @@ Demangler::~Demangler() = default;
std::string Demangler::Demangle(const SymbolTable& symbols, std::string Demangler::Demangle(const SymbolTable& symbols,
const std::string& str) const { const std::string& str) const {
auto ret = str; std::stringstream out;
size_t pos = 0; size_t pos = 0;
for (;;) { for (;;) {
auto idx = ret.find(kSymbol, pos); auto idx = str.find(kSymbol, pos);
if (idx == std::string::npos) if (idx == std::string::npos) {
out << str.substr(pos);
break; break;
}
out << str.substr(pos, idx - pos);
auto start_idx = idx + kSymbolLen; auto start_idx = idx + kSymbolLen;
auto end_idx = start_idx; 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++; end_idx++;
} }
auto len = end_idx - start_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)); Symbol sym(std::stoi(id));
auto name = symbols.NameFor(sym); out << symbols.NameFor(sym);
ret.replace(idx, end_idx - idx, name);
pos = idx + name.length(); pos = end_idx;
} }
return ret; return out.str();
} }
} // namespace tint } // namespace tint