From 160f72dc8e672ecca088c779dde2bc405ee91aae Mon Sep 17 00:00:00 2001 From: Benjamin Kramer Date: Sat, 9 Mar 2013 13:48:23 +0000 Subject: [PATCH] TLI: Microoptimize calls to strlen+memcmp to strncmp. The strlen+memcmp was hidden in a call to StringRef::operator==. We check if there are any null bytes in the string upfront so we can simplify the comparison Small speedup when compiling code with many function calls. llvm-svn: 176766 --- llvm/lib/Target/TargetLibraryInfo.cpp | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) diff --git a/llvm/lib/Target/TargetLibraryInfo.cpp b/llvm/lib/Target/TargetLibraryInfo.cpp index e5fdce2..c6cafe5 100644 --- a/llvm/lib/Target/TargetLibraryInfo.cpp +++ b/llvm/lib/Target/TargetLibraryInfo.cpp @@ -597,15 +597,37 @@ TargetLibraryInfo::TargetLibraryInfo(const TargetLibraryInfo &TLI) CustomNames = TLI.CustomNames; } +namespace { +struct StringComparator { + /// Compare two strings and return true if LHS is lexicographically less than + /// RHS. Requires that RHS doesn't contain any zero bytes. + bool operator()(const char *LHS, StringRef RHS) const { + // Compare prefixes with strncmp. If prefixes match we know that LHS is + // greater or equal to RHS as RHS can't contain any '\0'. + return std::strncmp(LHS, RHS.data(), RHS.size()) < 0; + } + + // Provided for compatibility with MSVC's debug mode. + bool operator()(StringRef LHS, const char *RHS) const { return LHS < RHS; } + bool operator()(StringRef LHS, StringRef RHS) const { return LHS < RHS; } +}; +} + bool TargetLibraryInfo::getLibFunc(StringRef funcName, LibFunc::Func &F) const { const char **Start = &StandardNames[0]; const char **End = &StandardNames[LibFunc::NumLibFuncs]; + + // Filter out empty names and names containing null bytes, those can't be in + // our table. + if (funcName.empty() || funcName.find('\0') != StringRef::npos) + return false; + // Check for \01 prefix that is used to mangle __asm declarations and // strip it if present. - if (!funcName.empty() && funcName.front() == '\01') + if (funcName.front() == '\01') funcName = funcName.substr(1); - const char **I = std::lower_bound(Start, End, funcName); + const char **I = std::lower_bound(Start, End, funcName, StringComparator()); if (I != End && *I == funcName) { F = (LibFunc::Func)(I - Start); return true; -- 2.7.4