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add new isSingleStringRef()/getSingleStringRef() methods to twine,

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and use them to avoid a copy of a string in getNameWithPrefix in
the common case.  It seems like Value::setName and other places 
should use this as well?

llvm-svn: 93301
This commit is contained in:
Chris Lattner 2010-01-13 07:12:06 +00:00
parent 951cfb6b8b
commit 9c1ca33ac3
2 changed files with 37 additions and 2 deletions
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30
include/llvm/ADT/Twine.h
View File

@ -329,6 +329,22 @@ namespace llvm {
bool isTriviallyEmpty() const {
return isNullary();
}
/// isSingleStringRef - Return true if this twine can be dynamically
/// accessed as a single StringRef value with getSingleStringRef().
bool isSingleStringRef() const {
if (getRHSKind() != EmptyKind) return false;
switch (getLHSKind()) {
case EmptyKind:
case CStringKind:
case StdStringKind:
case StringRefKind:
return true;
default:
return false;
}
}
/// @}
/// @name String Operations
@ -347,6 +363,20 @@ namespace llvm {
/// SmallVector.
void toVector(SmallVectorImpl<char> &Out) const;
/// getSingleStringRef - This returns the twine as a single StringRef. This
/// method is only valid if isSingleStringRef() is true.
StringRef getSingleStringRef() const {
assert(isSingleStringRef() &&"This cannot be had as a single stringref!");
switch (getLHSKind()) {
default: assert(0 && "Out of sync with isSingleStringRef");
case EmptyKind: return StringRef();
case CStringKind: return StringRef((const char*)LHS);
case StdStringKind: return StringRef(*(const std::string*)LHS);
case StringRefKind: return *(const StringRef*)LHS;
}
}
/// print - Write the concatenated string represented by this twine to the
/// stream \arg OS.
void print(raw_ostream &OS) const;

9
lib/VMCore/Mangler.cpp
View File

@ -188,8 +188,13 @@ std::string Mangler::getMangledName(const GlobalValue *GV, const char *Suffix,
void Mangler::getNameWithPrefix(SmallVectorImpl<char> &OutName,
const Twine &GVName, ManglerPrefixTy PrefixTy) {
SmallString<256> TmpData;
GVName.toVector(TmpData);
StringRef Name = TmpData.str();
StringRef Name;
if (GVName.isSingleStringRef())
Name = GVName.getSingleStringRef();
else {
GVName.toVector(TmpData);
Name = TmpData.str();
}
assert(!Name.empty() && "getNameWithPrefix requires non-empty name");
// If the global name is not led with \1, add the appropriate prefixes.