rewrite an O(N^2) algorithm to be O(n).
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@69500 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 3a1217a..2f57a49 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -3150,26 +3150,25 @@
// and then emit a note at each VLA being jumped out of.
S.Diag(DiagLoc, JumpDiag);
- // FIXME: This is N^2 and silly.
- while (1) {
- // Diagnose that the jump jumps over this declaration.
- const GotoScope &TargetScope = Scopes[ToScope];
- S.Diag(TargetScope.Loc, TargetScope.Diag);
+ // Eliminate the common prefix of the jump and the target. Start by
+ // linearizing both scopes, reversing them as we go.
+ std::vector<unsigned> FromScopes, ToScopes;
+ for (TestScope = FromScope; TestScope != ~0U;
+ TestScope = Scopes[TestScope].ParentScope)
+ FromScopes.push_back(TestScope);
+ for (TestScope = ToScope; TestScope != ~0U;
+ TestScope = Scopes[TestScope].ParentScope)
+ ToScopes.push_back(TestScope);
- // Walk out one level.
- ToScope = Scopes[ToScope].ParentScope;
- assert(ToScope != ~0U && "Didn't find top-level function scope?");
-
- // Check to see if the jump is valid now.
- unsigned TestScope = FromScope;
- while (TestScope != ~0U) {
- // If we found the jump target, the the jump became valid.
- if (TestScope == ToScope) return;
-
- // Otherwise, scan up the hierarchy.
- TestScope = Scopes[TestScope].ParentScope;
- }
+ // Remove any common entries (such as the top-level function scope).
+ while (!FromScopes.empty() && FromScopes.back() == ToScopes.back()) {
+ FromScopes.pop_back();
+ ToScopes.pop_back();
}
+
+ // Emit diagnostics for whatever is left in ToScopes.
+ for (unsigned i = 0, e = ToScopes.size(); i != e; ++i)
+ S.Diag(Scopes[ToScopes[i]].Loc, Scopes[ToScopes[i]].Diag);
}