6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-11-01 15:11:24 +00:00
Code Issues Projects Releases Wiki Activity

Avoid O(n*m) complexity in StringRef::find_first(_not)_of(StringRef).

Browse Source 
- Cache used characters in a bitset to reduce memory overhead to just 32 bytes.
- On my core2 this code is faster except when the checked string was very short
  (smaller than the list of delimiters).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111817 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer 2010-08-23 18:16:08 +00:00
parent 0e2c359a3e
commit 250eb005d9
2 changed files with 15 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/llvm/ADT/StringRef.h
View File

@ -238,7 +238,7 @@ namespace llvm {
/// find_first_of - Find the first character in the string that is in \arg
/// Chars, or npos if not found.
///
/// Note: O(size() * Chars.size())
/// Note: O(size() + Chars.size())
size_type find_first_of(StringRef Chars, size_t From = 0) const;
/// find_first_not_of - Find the first character in the string that is not
@ -248,7 +248,7 @@ namespace llvm {
/// find_first_not_of - Find the first character in the string that is not
/// in the string \arg Chars, or npos if not found.
///
/// Note: O(size() * Chars.size())
/// Note: O(size() + Chars.size())
size_type find_first_not_of(StringRef Chars, size_t From = 0) const;
/// @}

17
lib/Support/StringRef.cpp
View File

@ -9,6 +9,7 @@
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/APInt.h"
#include <bitset>
using namespace llvm;
@ -153,11 +154,15 @@ size_t StringRef::rfind(StringRef Str) const {
/// find_first_of - Find the first character in the string that is in \arg
/// Chars, or npos if not found.
///
/// Note: O(size() * Chars.size())
/// Note: O(size() + Chars.size())
StringRef::size_type StringRef::find_first_of(StringRef Chars,
size_t From) const {
std::bitset<1 << CHAR_BIT> CharBits;
for (size_type i = 0; i != Chars.size(); ++i)
CharBits.set((unsigned char)Chars[i]);
for (size_type i = min(From, Length), e = Length; i != e; ++i)
if (Chars.find(Data[i]) != npos)
if (CharBits.test((unsigned char)Data[i]))
return i;
return npos;
}
@ -174,11 +179,15 @@ StringRef::size_type StringRef::find_first_not_of(char C, size_t From) const {
/// find_first_not_of - Find the first character in the string that is not
/// in the string \arg Chars, or npos if not found.
///
/// Note: O(size() * Chars.size())
/// Note: O(size() + Chars.size())
StringRef::size_type StringRef::find_first_not_of(StringRef Chars,
size_t From) const {
std::bitset<1 << CHAR_BIT> CharBits;
for (size_type i = 0; i != Chars.size(); ++i)
CharBits.set((unsigned char)Chars[i]);
for (size_type i = min(From, Length), e = Length; i != e; ++i)
if (Chars.find(Data[i]) == npos)
if (!CharBits.test((unsigned char)Data[i]))
return i;
return npos;
}