Teach FileCheck to handle trailing CHECK-NOT patterns.

A CHECK-NOT pattern without a following CHECK pattern simply checks that the
pattern doesn't match before the end of the input file.

You can even have only CHECK-NOT patterns to check that strings appear nowhere
in the input file.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116592 91177308-0d34-0410-b5e6-96231b3b80d8

docs/CommandGuide/FileCheck.pod

@@ -165,7 +165,7 @@ directive in a file.
 =head2 The "CHECK-NOT:" directive
 
 The CHECK-NOT: directive is used to verify that a string doesn't occur
-between two matches (or the first match and the beginning of the file).  For
+between two matches (or before the first match, or after the last match).  For
 example, to verify that a load is removed by a transformation, a test like this
 can be used:
 

utils/FileCheck/FileCheck.cpp

@@ -50,6 +50,10 @@ NoCanonicalizeWhiteSpace("strict-whitespace",
 class Pattern {
   SMLoc PatternLoc;
 
+  /// MatchEOF - When set, this pattern only matches the end of file. This is
+  /// used for trailing CHECK-NOTs.
+  bool MatchEOF;
+
   /// FixedStr - If non-empty, this pattern is a fixed string match with the
   /// specified fixed string.
   StringRef FixedStr;
@@ -71,7 +75,7 @@ class Pattern {
 
 public:
 
-  Pattern() { }
+  Pattern(bool matchEOF = false) : MatchEOF(matchEOF) { }
 
   bool ParsePattern(StringRef PatternStr, SourceMgr &SM);
 
@@ -271,6 +275,12 @@ bool Pattern::AddRegExToRegEx(StringRef RegexStr, unsigned &CurParen,
 /// there is a match, the size of the matched string is returned in MatchLen.
 size_t Pattern::Match(StringRef Buffer, size_t &MatchLen,
                       StringMap<StringRef> &VariableTable) const {
+  // If this is the EOF pattern, match it immediately.
+  if (MatchEOF) {
+    MatchLen = 0;
+    return Buffer.size();
+  }
+
   // If this is a fixed string pattern, just match it now.
   if (!FixedStr.empty()) {
     MatchLen = FixedStr.size();
@@ -565,18 +575,20 @@ static bool ReadCheckFile(SourceMgr &SM,
     std::swap(NotMatches, CheckStrings.back().NotStrings);
   }
 
+  // Add an EOF pattern for any trailing CHECK-NOTs.
+  if (!NotMatches.empty()) {
+    CheckStrings.push_back(CheckString(Pattern(true),
+                                       SMLoc::getFromPointer(Buffer.data()),
+                                       false));
+    std::swap(NotMatches, CheckStrings.back().NotStrings);
+  }
+
   if (CheckStrings.empty()) {
     errs() << "error: no check strings found with prefix '" << CheckPrefix
            << ":'\n";
     return true;
   }
 
-  if (!NotMatches.empty()) {
-    errs() << "error: '" << CheckPrefix
-           << "-NOT:' not supported after last check line.\n";
-    return true;
-  }
-
   return false;
 }
 
@@ -662,10 +674,11 @@ int main(int argc, char **argv) {
 
     // Find StrNo in the file.
     size_t MatchLen = 0;
-    Buffer = Buffer.substr(CheckStr.Pat.Match(Buffer, MatchLen, VariableTable));
+    size_t MatchPos = CheckStr.Pat.Match(Buffer, MatchLen, VariableTable);
+    Buffer = Buffer.substr(MatchPos);
 
     // If we didn't find a match, reject the input.
-    if (Buffer.empty()) {
+    if (MatchPos == StringRef::npos) {
       PrintCheckFailed(SM, CheckStr, SearchFrom, VariableTable);
       return 1;
     }