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Replace an O(n^2) algorithm in areCompatObjCQualInterfaces with 

an O(n) algorithm by taking advantage of the fact that the
protocol qualifier list is already guaranteed sorted.

llvm-svn: 49312
This commit is contained in:
Chris Lattner 2008-04-07 05:05:41 +00:00
parent fde0761735
commit ae947fe3f9
1 changed files with 26 additions and 14 deletions
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40
clang/lib/AST/ASTContext.cpp
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@ -1478,21 +1478,33 @@ areCompatObjCQualInterfaces(const ObjCQualifiedInterfaceType *LHS,
if (!LHS->getDecl()->isSuperClassOf(RHS->getDecl()))
return false;
// All protocols in LHS must have a presence in RHS.
for (unsigned i = 0; i != LHS->getNumProtocols(); ++i) {
bool match = false;
ObjCProtocolDecl *lhsProto = LHS->getProtocols(i);
for (unsigned j = 0; j != RHS->getNumProtocols(); ++j) {
ObjCProtocolDecl *rhsProto = RHS->getProtocols(j);
if (lhsProto == rhsProto) {
match = true;
break;
}
}
if (!match)
return false;
// All protocols in LHS must have a presence in RHS. Since the protocol lists
// are both sorted alphabetically and have no duplicates, we can scan RHS and
// LHS in a single parallel scan until we run out of elements in LHS.
ObjCQualifiedInterfaceType::qual_iterator LHSPI = LHS->qual_begin();
ObjCQualifiedInterfaceType::qual_iterator LHSPE = LHS->qual_end();
ObjCQualifiedInterfaceType::qual_iterator RHSPI = RHS->qual_begin();
ObjCQualifiedInterfaceType::qual_iterator RHSPE = RHS->qual_end();
assert(LHSPI != LHSPE && "Empty LHS protocol list?");
ObjCProtocolDecl *LHSProto = *LHSPI;
while (RHSPI != RHSPE) {
ObjCProtocolDecl *RHSProto = *RHSPI++;
// If the RHS has a protocol that the LHS doesn't, ignore it.
if (RHSProto != LHSProto)
continue;
// Otherwise, the RHS does have this element.
++LHSPI;
if (LHSPI == LHSPE)
return true; // All protocols in LHS exist in RHS.
LHSProto = *LHSPI;
}
return true;
// If we got here, we didn't find one of the LHS's protocols in the RHS list.
return false;
}
/// ProtocolCompatibleWithProtocol - return 'true' if 'lProto' is in the