Add a stop gap to Sema::CorrectTypo() to correct only up to 20 typos.
This is to address a serious performance problem observed when running
'clang -fsyntax-only' on really broken source files.  In one case,
repeatedly calling CorrectTypo() caused one source file to be rejected
after 2 minutes instead of 1 second.

This patch causes typo correction to take neglible time on that file
while still providing correction results for the first 20 cases.  I
felt this was a reasonable number for moderately broken source files.

I don't claim this is the best solution.  Comments welcome.  It is
necessary for us to address this issue because it is a serious
performance problem.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@95049 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/Sema.cpp b/lib/Sema/Sema.cpp
index c0e7572..903b987 100644
--- a/lib/Sema/Sema.cpp
+++ b/lib/Sema/Sema.cpp
@@ -364,7 +364,7 @@
     GlobalNewDeleteDeclared(false), 
     CompleteTranslationUnit(CompleteTranslationUnit),
     NumSFINAEErrors(0), NonInstantiationEntries(0), 
-    CurrentInstantiationScope(0) 
+    CurrentInstantiationScope(0), TyposCorrected(0)
 {
   TUScope = 0;
   if (getLangOptions().CPlusPlus)