[FileCheck] introduce CHECK-COUNT-<num> repetition directive

[fedor.sergeev]

Summary

In some cases it is desirable to match the same pattern repeatedly
many times. Currently the only way to do it is to copy the same
check pattern as many times as needed. And that gets pretty unwieldy when
count is high enough that counting these patterns at a single glance is nontrivial.

Introducing CHECK-COUNT-<num> directive which acts like a plain CHECK
directive yet matches the same pattern exactly <num> times.

Extended FileCheckType to a struct to add Count there.
Changed some parsing routines to handle non-fixed length of directive
(all currently existing directives were fixed-length).

The code is generic enough to allow future support for COUNT in more
than just PlainCheck directives.

See motivating example for this feature in reviews.llvm.org/D54223.

[fedor.sergeev]

I know, it needs documentation changes :)

[chandlerc]

Seems pretty reasonable to me. Pretty minor things below...

include/llvm/Support/FileCheck.h

62–81

nit: blank line here

69

I'd prefer to use an int throughout for this.

lib/Support/FileCheck.cpp

594

int64_t?

865

clang-format

[fedor.sergeev]

addressing comments, clang-formatted, added std includes, some minor stuff

[fedor.sergeev]

addings docs

[dblaikie]

lib/Support/FileCheck.cpp

586–589

Bit inconsistent (with LLVM style, and within this file specifically) to have {} on this single-line block (& another further down (consumeInteger))?

707

Does this work as {"", ""}? or does that do the wrong thing/not compile?

763–766

I'd probably use a conditional operator here, but not a huge deal by any means if you prefer it this way.

[fedor.sergeev]

lib/Support/FileCheck.cpp

586–589

This one - you'r right.
consumeInteger - I wonder, I do have one comment and one statement there, does it count as a single-line block?

707

Direct shorter equivalent would be
{ {}, {} }
And this one:
{ "", "" }
is a tad different, by providing a non-null data pointer (to empty constant string).
For the purpose of this change all these are the same.

As you see, originally there was just StringRef(), thats why I chose my version.
I dont feel strongly about either of these versions.

[fedor.sergeev]

minor cleanup

[chandlerc]

FWIW, this looks really good to me. I'd be fine with this going in as-is and any further improvements suggested by David as follow-ups. Feel free to submit with comments addressed.

lib/Support/FileCheck.cpp

586–589

I personally usually omit braces unless it is in a surrounding context that makes this deeply confusing. (weird loop nesting, dense other conditions, etc)

707

FWIW, I prefer something other than {"", ""}. I have a mild preference for {StringRef(), StringRef()}, but it is very mild.

[dblaikie]

In D54336#1294282, @chandlerc wrote:

FWIW, this looks really good to me. I'd be fine with this going in as-is and any further improvements suggested by David as follow-ups. Feel free to submit with comments addressed.

Yeah, nothing more from me - thanks!

lib/Support/FileCheck.cpp

586–589

Yeah, opinions differ here - some folks only omit braces on single line scopes, some omit them from any single statement (whether or not the statement is wrapped over multiple lines, or there are comment lines, etc). I don't feel strongly either - I just hadn't noticed/thought about the fact that the other was multi-line-single-statement block.

707

Fair enough, I don't feel too strongly (if there's any specific motivation for the aversion to {"", ""} I'd be curious to hear it, for reference/understanding/etc).

[fedor.sergeev]

lib/Support/FileCheck.cpp

707

One particular motivating aspect is that "" creates a special object and that is only to create an empty StringRef which does not need anything than just length == 0.

Asked people on IRC and none of them chose "","" variant ;)
Also, Zygoloid mentioned that { "", "" } could be treated as a call to constructor that takes two iterators (there is none such constructor presently though).

Anyway I will go for the most uncontroversial StringRef() version, despite it being somewhat chatty. I dont mind typing a few extra characters :)

include/llvm/Support/FileCheck.h

 };
 
 
 //===----------------------------------------------------------------------===//
 // Pattern Handling Code.
 //===----------------------------------------------------------------------===//
 
 namespace Check {
-enum FileCheckType {
+
+enum FileCheckKind {
   CheckNone = 0,
   CheckPlain,
   CheckNext,
   CheckSame,
   CheckNot,
   CheckDAG,
   CheckLabel,
   CheckEmpty,
 
   /// Indicates the pattern only matches the end of file. This is used for
   /// trailing CHECK-NOTs.
   CheckEOF,
 
   /// Marks when parsing found a -NOT check combined with another CHECK suffix.
-  CheckBadNot
+  CheckBadNot,
+
+  /// Marks when parsing found a -COUNT directive with invalid count value.
+  CheckBadCount
+};
+
+class FileCheckType {
+  FileCheckKind Kind;
+  int Count; //< optional Count for some checks
+
+public:
+  FileCheckType(FileCheckKind Kind = CheckNone) : Kind(Kind), Count(1) {}
+  FileCheckType(const FileCheckType &) = default;
+
+  operator FileCheckKind() const { return Kind; }
+
+  int getCount() const { return Count; }
+  FileCheckType &setCount(int C);
+
+  std::string getDescription(StringRef Prefix) const;
 };
 }
 
 class FileCheckPattern {
   SMLoc PatternLoc;
 
   /// A fixed string to match as the pattern or empty if this pattern requires
   /// a regex match.
void PrintFuzzyMatch(const SourceMgr &SM, StringRef Buffer,
                        const StringMap<StringRef> &VariableTable) const;
 
   bool hasVariable() const {
     return !(VariableUses.empty() && VariableDefs.empty());
   }
 
   Check::FileCheckType getCheckTy() const { return CheckTy; }
 
+  int getCount() const { return CheckTy.getCount(); }
+
 private:
   bool AddRegExToRegEx(StringRef RS, unsigned &CurParen, SourceMgr &SM);
   void AddBackrefToRegEx(unsigned BackrefNum);
   unsigned
   ComputeMatchDistance(StringRef Buffer,
                        const StringMap<StringRef> &VariableTable) const;
   bool EvaluateExpression(StringRef Expr, std::string &Value) const;
   size_t FindRegexVarEnd(StringRef Str, SourceMgr &SM);

lib/Support/FileCheck.cpp

 // contains the expected content.  This is useful for regression tests etc.
 //
 // This file implements most of the API that will be used by the FileCheck utility
 // as well as various unittests.
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Support/FileCheck.h"
 #include "llvm/ADT/StringSet.h"
+#include "llvm/Support/FormatVariadic.h"
+#include <cstdint>
 #include <list>
 #include <map>
+#include <tuple>
+#include <utility>
 
 using namespace llvm;
 
 /// Parses the given string into the Pattern.
 ///
 /// \p Prefix provides which prefix is being matched, \p SM provides the
 /// SourceMgr used for error reports, and \p LineNumber is the line number in
 /// the input file from which the pattern string was read. Returns true in
llvm::FileCheck::CanonicalizeFile(MemoryBuffer &MB,
   OutputBuffer.push_back('\0');
   return StringRef(OutputBuffer.data(), OutputBuffer.size() - 1);
 }
 
 static bool IsPartOfWord(char c) {
   return (isalnum(c) || c == '-' || c == '_');
 }
 
-// Get the size of the prefix extension.
-static size_t CheckTypeSize(Check::FileCheckType Ty) {
-  switch (Ty) {
-  case Check::CheckNone:
-  case Check::CheckBadNot:
-    return 0;
-
-  case Check::CheckPlain:
-    return sizeof(":") - 1;
-
-  case Check::CheckNext:
-    return sizeof("-NEXT:") - 1;
-
-  case Check::CheckSame:
-    return sizeof("-SAME:") - 1;
-
-  case Check::CheckNot:
-    return sizeof("-NOT:") - 1;
-
-  case Check::CheckDAG:
-    return sizeof("-DAG:") - 1;
-
-  case Check::CheckLabel:
-    return sizeof("-LABEL:") - 1;
-
-  case Check::CheckEmpty:
-    return sizeof("-EMPTY:") - 1;
-
-  case Check::CheckEOF:
-    llvm_unreachable("Should not be using EOF size");
-  }
-
-  llvm_unreachable("Bad check type");
+Check::FileCheckType &Check::FileCheckType::setCount(int C) {
+  assert(Count > 0 || "zero and negative counts are not supported");
+  assert((C == 1 || Kind == CheckPlain) &&
+         "count supported only for plain CHECK directives");
+  Count = C;
+  return *this;
 }
 
 // Get a description of the type.
-static std::string CheckTypeName(StringRef Prefix, Check::FileCheckType Ty) {
-  switch (Ty) {
+std::string Check::FileCheckType::getDescription(StringRef Prefix) const {
+  switch (Kind) {
   case Check::CheckNone:
     return "invalid";
   case Check::CheckPlain:
+    if (Count > 1)
+      return Prefix.str() + "-COUNT";
     return Prefix;
   case Check::CheckNext:
     return Prefix.str() + "-NEXT";
   case Check::CheckSame:
     return Prefix.str() + "-SAME";
   case Check::CheckNot:
     return Prefix.str() + "-NOT";
   case Check::CheckDAG:
     return Prefix.str() + "-DAG";
   case Check::CheckLabel:
     return Prefix.str() + "-LABEL";
   case Check::CheckEmpty:
     return Prefix.str() + "-EMPTY";
   case Check::CheckEOF:
     return "implicit EOF";
   case Check::CheckBadNot:
     return "bad NOT";
+  case Check::CheckBadCount:
+    return "bad COUNT";
   }
   llvm_unreachable("unknown FileCheckType");
 }
 
-static Check::FileCheckType FindCheckType(StringRef Buffer, StringRef Prefix) {
+static std::pair<Check::FileCheckType, StringRef>
+FindCheckType(StringRef Buffer, StringRef Prefix) {
   if (Buffer.size() <= Prefix.size())
-    return Check::CheckNone;
+    return {Check::CheckNone, StringRef()};
 
   char NextChar = Buffer[Prefix.size()];
 
+  StringRef Rest = Buffer.drop_front(Prefix.size() + 1);
   // Verify that the : is present after the prefix.
-  if (NextChar == ':')
-    return Check::CheckPlain;
+  if (NextChar == ':') {
+    return {Check::CheckPlain, Rest};
+  }
 
   if (NextChar != '-')
-    return Check::CheckNone;
+    return {Check::CheckNone, StringRef()};
 
-  StringRef Rest = Buffer.drop_front(Prefix.size() + 1);
-  if (Rest.startswith("NEXT:"))
-    return Check::CheckNext;
+  if (Rest.consume_front("COUNT-")) {
+    int64_t Count;
+    if (Rest.consumeInteger(10, Count)) {
+      // error in string parsing
+      return {Check::CheckBadCount, Rest};
+    }
+    if (Count <= 0 || Count > INT32_MAX)
+      return {Check::CheckBadCount, Rest};
+    if (!Rest.consume_front(":"))
+      return {Check::CheckBadCount, Rest};
+    return {Check::FileCheckType(Check::CheckPlain).setCount(Count), Rest};
+  }
+  if (Rest.consume_front("NEXT:"))
+    return {Check::CheckNext, Rest};
 
-  if (Rest.startswith("SAME:"))
-    return Check::CheckSame;
+  if (Rest.consume_front("SAME:"))
+    return {Check::CheckSame, Rest};
 
-  if (Rest.startswith("NOT:"))
-    return Check::CheckNot;
+  if (Rest.consume_front("NOT:"))
+    return {Check::CheckNot, Rest};
 
-  if (Rest.startswith("DAG:"))
-    return Check::CheckDAG;
+  if (Rest.consume_front("DAG:"))
+    return {Check::CheckDAG, Rest};
 
-  if (Rest.startswith("LABEL:"))
-    return Check::CheckLabel;
+  if (Rest.consume_front("LABEL:"))
+    return {Check::CheckLabel, Rest};
 
-  if (Rest.startswith("EMPTY:"))
-    return Check::CheckEmpty;
+  if (Rest.consume_front("EMPTY:"))
+    return {Check::CheckEmpty, Rest};
 
   // You can't combine -NOT with another suffix.
   if (Rest.startswith("DAG-NOT:") || Rest.startswith("NOT-DAG:") ||
       Rest.startswith("NEXT-NOT:") || Rest.startswith("NOT-NEXT:") ||
       Rest.startswith("SAME-NOT:") || Rest.startswith("NOT-SAME:") ||
       Rest.startswith("EMPTY-NOT:") || Rest.startswith("NOT-EMPTY:"))
-    return Check::CheckBadNot;
+    return {Check::CheckBadNot, Rest};
 
-  return Check::CheckNone;
+  return {Check::CheckNone, Rest};
 }
 
 // From the given position, find the next character after the word.
 static size_t SkipWord(StringRef Str, size_t Loc) {
   while (Loc < Str.size() && IsPartOfWord(Str[Loc]))
     ++Loc;
   return Loc;
 }
 
 /// Search the buffer for the first prefix in the prefix regular expression.
 ///
 /// This searches the buffer using the provided regular expression, however it
 /// enforces constraints beyond that:
 /// 1) The found prefix must not be a suffix of something that looks like
 ///    a valid prefix.
 /// 2) The found prefix must be followed by a valid check type suffix using \c
 ///    FindCheckType above.
 ///
-/// The first match of the regular expression to satisfy these two is returned,
-/// otherwise an empty StringRef is returned to indicate failure.
+/// Returns a pair of StringRefs into the Buffer, which combines:
+///   - the first match of the regular expression to satisfy these two is
+///   returned,
+///     otherwise an empty StringRef is returned to indicate failure.
+///   - buffer rewound to the location right after parsed suffix, for parsing
+///     to continue from
 ///
 /// If this routine returns a valid prefix, it will also shrink \p Buffer to
 /// start at the beginning of the returned prefix, increment \p LineNumber for
 /// each new line consumed from \p Buffer, and set \p CheckTy to the type of
 /// check found by examining the suffix.
 ///
 /// If no valid prefix is found, the state of Buffer, LineNumber, and CheckTy
 /// is unspecified.
-static StringRef FindFirstMatchingPrefix(Regex &PrefixRE, StringRef &Buffer,
-                                         unsigned &LineNumber,
-                                         Check::FileCheckType &CheckTy) {
+static std::pair<StringRef, StringRef>
+FindFirstMatchingPrefix(Regex &PrefixRE, StringRef &Buffer,
+                        unsigned &LineNumber, Check::FileCheckType &CheckTy) {
   SmallVector<StringRef, 2> Matches;
 
   while (!Buffer.empty()) {
     // Find the first (longest) match using the RE.
     if (!PrefixRE.match(Buffer, &Matches))
       // No match at all, bail.
-      return StringRef();
+      return {StringRef(), StringRef()};
 
     StringRef Prefix = Matches[0];
     Matches.clear();
 
     assert(Prefix.data() >= Buffer.data() &&
            Prefix.data() < Buffer.data() + Buffer.size() &&
            "Prefix doesn't start inside of buffer!");
     size_t Loc = Prefix.data() - Buffer.data();
     StringRef Skipped = Buffer.substr(0, Loc);
     Buffer = Buffer.drop_front(Loc);
     LineNumber += Skipped.count('\n');
 
     // Check that the matched prefix isn't a suffix of some other check-like
     // word.
     // FIXME: This is a very ad-hoc check. it would be better handled in some
     // other way. Among other things it seems hard to distinguish between
     // intentional and unintentional uses of this feature.
     if (Skipped.empty() || !IsPartOfWord(Skipped.back())) {
       // Now extract the type.
-      CheckTy = FindCheckType(Buffer, Prefix);
+      StringRef AfterSuffix;
+      std::tie(CheckTy, AfterSuffix) = FindCheckType(Buffer, Prefix);
 
       // If we've found a valid check type for this prefix, we're done.
       if (CheckTy != Check::CheckNone)
-        return Prefix;
+        return {Prefix, AfterSuffix};
     }
 
     // If we didn't successfully find a prefix, we need to skip this invalid
     // prefix and continue scanning. We directly skip the prefix that was
     // matched and any additional parts of that check-like word.
     Buffer = Buffer.drop_front(SkipWord(Buffer, Prefix.size()));
   }
 
   // We ran out of buffer while skipping partial matches so give up.
-  return StringRef();
+  return {StringRef(), StringRef()};
 }
 
 /// Read the check file, which specifies the sequence of expected strings.
 ///
 /// The strings are added to the CheckStrings vector. Returns true in case of
 /// an error, false otherwise.
 bool llvm::FileCheck::ReadCheckFile(SourceMgr &SM, StringRef Buffer,
                                     Regex &PrefixRE,
bool llvm::FileCheck::ReadCheckFile(SourceMgr &SM, StringRef Buffer,
   // LineNumber keeps track of the line on which CheckPrefix instances are
   // found.
   unsigned LineNumber = 1;
 
   while (1) {
     Check::FileCheckType CheckTy;
 
     // See if a prefix occurs in the memory buffer.
-    StringRef UsedPrefix = FindFirstMatchingPrefix(PrefixRE, Buffer, LineNumber,
-                                                   CheckTy);
+    StringRef UsedPrefix;
+    StringRef AfterSuffix;
+    std::tie(UsedPrefix, AfterSuffix) =
+        FindFirstMatchingPrefix(PrefixRE, Buffer, LineNumber, CheckTy);
     if (UsedPrefix.empty())
       break;
     assert(UsedPrefix.data() == Buffer.data() &&
            "Failed to move Buffer's start forward, or pointed prefix outside "
            "of the buffer!");
+    assert(AfterSuffix.data() >= Buffer.data() &&
+           AfterSuffix.data() < Buffer.data() + Buffer.size() &&
+           "Parsing after suffix doesn't start inside of buffer!");
 
     // Location to use for error messages.
     const char *UsedPrefixStart = UsedPrefix.data();
 
-    // Skip the buffer to the end.
-    Buffer = Buffer.drop_front(UsedPrefix.size() + CheckTypeSize(CheckTy));
+    // Skip the buffer to the end of parsed suffix (or just prefix, if no good
+    // suffix was processed).
+    if (AfterSuffix.empty())
+      Buffer = Buffer.drop_front(UsedPrefix.size());
+    else
+      Buffer = AfterSuffix;
 
     // Complain about useful-looking but unsupported suffixes.
     if (CheckTy == Check::CheckBadNot) {
       SM.PrintMessage(SMLoc::getFromPointer(Buffer.data()), SourceMgr::DK_Error,
                       "unsupported -NOT combo on prefix '" + UsedPrefix + "'");
       return true;
     }
 
+    // Complain about invalid count specification.
+    if (CheckTy == Check::CheckBadCount) {
+      SM.PrintMessage(SMLoc::getFromPointer(Buffer.data()), SourceMgr::DK_Error,
+                      "invalid count in -COUNT specification on prefix '" +
+                          UsedPrefix + "'");
+      return true;
+    }
+
     // Okay, we found the prefix, yay. Remember the rest of the line, but ignore
     // leading whitespace.
     if (!(Req.NoCanonicalizeWhiteSpace && Req.MatchFullLines))
       Buffer = Buffer.substr(Buffer.find_first_not_of(" \t"));
 
     // Scan ahead to the end of line.
     size_t EOL = Buffer.find_first_of("\n\r");
 
if (CheckStrings.empty()) {
     return true;
   }
 
   return false;
 }
 
 static void PrintMatch(bool ExpectedMatch, const SourceMgr &SM,
                        StringRef Prefix, SMLoc Loc, const FileCheckPattern &Pat,
-                       StringRef Buffer, StringMap<StringRef> &VariableTable,
-                       size_t MatchPos, size_t MatchLen,
-                       const FileCheckRequest &Req) {
+                       int MatchedCount, StringRef Buffer,
+                       StringMap<StringRef> &VariableTable, size_t MatchPos,
+                       size_t MatchLen, const FileCheckRequest &Req) {
   if (ExpectedMatch) {
     if (!Req.Verbose)
       return;
     if (!Req.VerboseVerbose && Pat.getCheckTy() == Check::CheckEOF)
       return;
   }
   SMLoc MatchStart = SMLoc::getFromPointer(Buffer.data() + MatchPos);
   SMLoc MatchEnd = SMLoc::getFromPointer(Buffer.data() + MatchPos + MatchLen);
   SMRange MatchRange(MatchStart, MatchEnd);
+  std::string Message = formatv("{0}: {1} string found in input",
+                                Pat.getCheckTy().getDescription(Prefix),
+                                (ExpectedMatch ? "expected" : "excluded"))
+                            .str();
+  if (Pat.getCount() > 1)
+    Message += formatv(" ({0} out of {1})", MatchedCount, Pat.getCount()).str();
+
   SM.PrintMessage(
-      Loc, ExpectedMatch ? SourceMgr::DK_Remark : SourceMgr::DK_Error,
-      CheckTypeName(Prefix, Pat.getCheckTy()) + ": " +
-          (ExpectedMatch ? "expected" : "excluded") +
-          " string found in input");
+      Loc, ExpectedMatch ? SourceMgr::DK_Remark : SourceMgr::DK_Error, Message);
   SM.PrintMessage(MatchStart, SourceMgr::DK_Note, "found here", {MatchRange});
   Pat.PrintVariableUses(SM, Buffer, VariableTable, MatchRange);
 }
 
 static void PrintMatch(bool ExpectedMatch, const SourceMgr &SM,
-                       const FileCheckString &CheckStr, StringRef Buffer,
-                       StringMap<StringRef> &VariableTable, size_t MatchPos,
-                       size_t MatchLen, FileCheckRequest &Req) {
+                       const FileCheckString &CheckStr, int MatchedCount,
+                       StringRef Buffer, StringMap<StringRef> &VariableTable,
+                       size_t MatchPos, size_t MatchLen,
+                       FileCheckRequest &Req) {
   PrintMatch(ExpectedMatch, SM, CheckStr.Prefix, CheckStr.Loc, CheckStr.Pat,
-             Buffer, VariableTable, MatchPos, MatchLen, Req);
+             MatchedCount, Buffer, VariableTable, MatchPos, MatchLen, Req);
 }
 
 static void PrintNoMatch(bool ExpectedMatch, const SourceMgr &SM,
-                         StringRef Prefix, SMLoc Loc, const FileCheckPattern &Pat,
-                         StringRef Buffer,
-                         StringMap<StringRef> &VariableTable,
+                         StringRef Prefix, SMLoc Loc,
+                         const FileCheckPattern &Pat, int MatchedCount,
+                         StringRef Buffer, StringMap<StringRef> &VariableTable,
                          bool VerboseVerbose) {
   if (!ExpectedMatch && !VerboseVerbose)
     return;
 
   // Otherwise, we have an error, emit an error message.
-  SM.PrintMessage(Loc,
-                  ExpectedMatch ? SourceMgr::DK_Error : SourceMgr::DK_Remark,
-                  CheckTypeName(Prefix, Pat.getCheckTy()) + ": " +
-                      (ExpectedMatch ? "expected" : "excluded") +
-                      " string not found in input");
+  std::string Message = formatv("{0}: {1} string not found in input",
+                                Pat.getCheckTy().getDescription(Prefix),
+                                (ExpectedMatch ? "expected" : "excluded"))
+                            .str();
+  if (Pat.getCount() > 1)
+    Message += formatv(" ({0} out of {1})", MatchedCount, Pat.getCount()).str();
+
+  SM.PrintMessage(
+      Loc, ExpectedMatch ? SourceMgr::DK_Error : SourceMgr::DK_Remark, Message);
 
   // Print the "scanning from here" line.  If the current position is at the
   // end of a line, advance to the start of the next line.
   Buffer = Buffer.substr(Buffer.find_first_not_of(" \t\n\r"));
 
   SM.PrintMessage(SMLoc::getFromPointer(Buffer.data()), SourceMgr::DK_Note,
                   "scanning from here");
 
   // Allow the pattern to print additional information if desired.
   Pat.PrintVariableUses(SM, Buffer, VariableTable);
   if (ExpectedMatch)
     Pat.PrintFuzzyMatch(SM, Buffer, VariableTable);
 }
 
 static void PrintNoMatch(bool ExpectedMatch, const SourceMgr &SM,
-                         const FileCheckString &CheckStr, StringRef Buffer,
-                         StringMap<StringRef> &VariableTable,
+                         const FileCheckString &CheckStr, int MatchedCount,
+                         StringRef Buffer, StringMap<StringRef> &VariableTable,
                          bool VerboseVerbose) {
   PrintNoMatch(ExpectedMatch, SM, CheckStr.Prefix, CheckStr.Loc, CheckStr.Pat,
-               Buffer, VariableTable, VerboseVerbose);
+               MatchedCount, Buffer, VariableTable, VerboseVerbose);
 }
 
 /// Count the number of newlines in the specified range.
 static unsigned CountNumNewlinesBetween(StringRef Range,
                                         const char *&FirstNewLine) {
   unsigned NumNewLines = 0;
   while (1) {
     // Scan for newline.
size_t FileCheckString::Check(const SourceMgr &SM, StringRef Buffer,
   if (!IsLabelScanMode) {
     // Match "dag strings" (with mixed "not strings" if any).
     LastPos = CheckDag(SM, Buffer, NotStrings, VariableTable, Req);
     if (LastPos == StringRef::npos)
       return StringRef::npos;
   }
 
   // Match itself from the last position after matching CHECK-DAG.
-  StringRef MatchBuffer = Buffer.substr(LastPos);
-  size_t MatchPos = Pat.Match(MatchBuffer, MatchLen, VariableTable);
+  size_t LastMatchEnd = LastPos;
+  size_t FirstMatchPos = 0;
+  // Go match the pattern Count times. Majority of patterns only match with
+  // count 1 though.
+  assert(Pat.getCount() != 0 && "pattern count can not be zero");
+  for (int i = 1; i <= Pat.getCount(); i++) {
+    StringRef MatchBuffer = Buffer.substr(LastMatchEnd);
+    size_t CurrentMatchLen;
+    // get a match at current start point
+    size_t MatchPos = Pat.Match(MatchBuffer, CurrentMatchLen, VariableTable);
+    if (i == 1)
+      FirstMatchPos = LastPos + MatchPos;
+
+    // report
     if (MatchPos == StringRef::npos) {
-    PrintNoMatch(true, SM, *this, MatchBuffer, VariableTable, Req.VerboseVerbose);
+      PrintNoMatch(true, SM, *this, i, MatchBuffer, VariableTable,
+                   Req.VerboseVerbose);
       return StringRef::npos;
     }
-  PrintMatch(true, SM, *this, MatchBuffer, VariableTable, MatchPos, MatchLen, Req);
+    PrintMatch(true, SM, *this, i, MatchBuffer, VariableTable, MatchPos,
+               CurrentMatchLen, Req);
+
+    // move start point after the match
+    LastMatchEnd += MatchPos + CurrentMatchLen;
+  }
+  // Full match len counts from first match pos.
+  MatchLen = LastMatchEnd - FirstMatchPos;
 
   // Similar to the above, in "label-scan mode" we can't yet handle CHECK-NEXT
   // or CHECK-NOT
   if (!IsLabelScanMode) {
-    StringRef SkippedRegion = Buffer.substr(LastPos, MatchPos);
+    StringRef SkippedRegion = Buffer.substr(LastPos, FirstMatchPos - LastPos);
 
     // If this check is a "CHECK-NEXT", verify that the previous match was on
     // the previous line (i.e. that there is one newline between them).
     if (CheckNext(SM, SkippedRegion))
       return StringRef::npos;
 
     // If this check is a "CHECK-SAME", verify that the previous match was on
     // the same line (i.e. that there is no newline between them).
     if (CheckSame(SM, SkippedRegion))
       return StringRef::npos;
 
     // If this match had "not strings", verify that they don't exist in the
     // skipped region.
     if (CheckNot(SM, SkippedRegion, NotStrings, VariableTable, Req))
       return StringRef::npos;
   }
 
-  return LastPos + MatchPos;
+  return FirstMatchPos;
 }
 
 /// Verify there is a single line in the given buffer.
 bool FileCheckString::CheckNext(const SourceMgr &SM, StringRef Buffer) const {
   if (Pat.getCheckTy() != Check::CheckNext &&
       Pat.getCheckTy() != Check::CheckEmpty)
     return false;
 
bool FileCheckString::CheckNot(const SourceMgr &SM, StringRef Buffer,
                            const FileCheckRequest &Req) const {
   for (const FileCheckPattern *Pat : NotStrings) {
     assert((Pat->getCheckTy() == Check::CheckNot) && "Expect CHECK-NOT!");
 
     size_t MatchLen = 0;
     size_t Pos = Pat->Match(Buffer, MatchLen, VariableTable);
 
     if (Pos == StringRef::npos) {
-      PrintNoMatch(false, SM, Prefix, Pat->getLoc(), *Pat, Buffer,
+      PrintNoMatch(false, SM, Prefix, Pat->getLoc(), *Pat, 1, Buffer,
                    VariableTable, Req.VerboseVerbose);
       continue;
     }
 
-    PrintMatch(false, SM, Prefix, Pat->getLoc(), *Pat, Buffer, VariableTable,
+    PrintMatch(false, SM, Prefix, Pat->getLoc(), *Pat, 1, Buffer, VariableTable,
                Pos, MatchLen, Req);
 
     return true;
   }
 
   return false;
 }
 
for (auto PatItr = DagNotStrings.begin(), PatEnd = DagNotStrings.end();
     // Search for a match that doesn't overlap a previous match in this
     // CHECK-DAG group.
     for (auto MI = MatchRanges.begin(), ME = MatchRanges.end(); true; ++MI) {
       StringRef MatchBuffer = Buffer.substr(MatchPos);
       size_t MatchPosBuf = Pat.Match(MatchBuffer, MatchLen, VariableTable);
       // With a group of CHECK-DAGs, a single mismatching means the match on
       // that group of CHECK-DAGs fails immediately.
       if (MatchPosBuf == StringRef::npos) {
-        PrintNoMatch(true, SM, Prefix, Pat.getLoc(), Pat, MatchBuffer,
+        PrintNoMatch(true, SM, Prefix, Pat.getLoc(), Pat, 1, MatchBuffer,
                      VariableTable, Req.VerboseVerbose);
         return StringRef::npos;
       }
       // Re-calc it as the offset relative to the start of the original string.
       MatchPos += MatchPosBuf;
       if (Req.VerboseVerbose)
-        PrintMatch(true, SM, Prefix, Pat.getLoc(), Pat, Buffer, VariableTable,
-                   MatchPos, MatchLen, Req);
+        PrintMatch(true, SM, Prefix, Pat.getLoc(), Pat, 1, Buffer,
+                   VariableTable, MatchPos, MatchLen, Req);
       MatchRange M{MatchPos, MatchPos + MatchLen};
       if (Req.AllowDeprecatedDagOverlap) {
         // We don't need to track all matches in this mode, so we just maintain
         // one match range that encompasses the current CHECK-DAG group's
         // matches.
         if (MatchRanges.empty())
           MatchRanges.insert(MatchRanges.end(), M);
         else {
for (auto MI = MatchRanges.begin(), ME = MatchRanges.end(); true; ++MI) {
         SMRange OldRange(OldStart, OldEnd);
         SM.PrintMessage(OldStart, SourceMgr::DK_Note,
                         "match discarded, overlaps earlier DAG match here",
                         {OldRange});
       }
       MatchPos = MI->End;
     }
     if (!Req.VerboseVerbose)
-      PrintMatch(true, SM, Prefix, Pat.getLoc(), Pat, Buffer, VariableTable,
+      PrintMatch(true, SM, Prefix, Pat.getLoc(), Pat, 1, Buffer, VariableTable,
                  MatchPos, MatchLen, Req);
 
     // Handle the end of a CHECK-DAG group.
     if (std::next(PatItr) == PatEnd ||
         std::next(PatItr)->getCheckTy() == Check::CheckNot) {
       if (!NotStrings.empty()) {
         // If there are CHECK-NOTs between two CHECK-DAGs or from CHECK to
         // CHECK-DAG, verify that there are no 'not' strings occurred in that

test/FileCheck/check-count.txt

+;
+; Basic error checking.
+;
+
+this is something else
+
+; RUN: not FileCheck %s --input-file %s --check-prefix=CHECK-ERR1 2>&1 | FileCheck %s --check-prefix=ERRCOUNT1
+CHECK-ERR1-COUNT-xx: this
+ERRCOUNT1: [[@LINE-1]]:18: error: invalid count in -COUNT specification on prefix 'CHECK-ERR1'
+
+; RUN: not FileCheck %s --input-file %s --check-prefix=CHECK-ERR2 2>&1 | FileCheck %s --check-prefix=ERRCOUNT2
+CHECK-ERR2-COUNT-0x1: something
+ERRCOUNT2: [[@LINE-1]]:19: error: invalid count in -COUNT specification on prefix 'CHECK-ERR2'
+
+; RUN: not FileCheck %s --input-file %s --check-prefix=CHECK-ERR3 2>&1 | FileCheck %s --check-prefix=ERRCOUNT3
+CHECK-ERR3-COUNT-100x: else
+ERRCOUNT3: [[@LINE-1]]:21: error: invalid count in -COUNT specification on prefix 'CHECK-ERR3'
+
+; RUN: not FileCheck %s --input-file %s --check-prefix=CHECK-ERR4 2>&1 | FileCheck %s --check-prefix=ERRCOUNT4
+CHECK-ERR4-COUNT-0: else
+ERRCOUNT4: [[@LINE-1]]:19: error: invalid count in -COUNT specification on prefix 'CHECK-ERR4'
+
+;
+; Main functionality
+;
+
+this is duplicate
+this is duplicate
+this is not duplicate
+this is duplicate
+this is duplicate
+this is duplicate
+
+; RUN: FileCheck %s --input-file %s --check-prefix=CHECK-CNT1
+CHECK-CNT1-COUNT-1: this is duplicate
+CHECK-CNT1:       this is duplicate
+CHECK-CNT1-NEXT:    this is not duplicate
+
+; RUN: FileCheck %s --input-file %s --check-prefix=CHECK-CNT2
+CHECK-CNT2-COUNT-2: this is duplicate
+CHECK-CNT2:         this is not duplicate
+
+; RUN: FileCheck %s --input-file %s --check-prefix=CHECK-CNT3
+CHECK-CNT3-COUNT-2: this is duplicate
+CHECK-CNT3:         this is not duplicate
+CHECK-CNT3-COUNT-3: this is duplicate
+CHECK-CNT3-NOT:     {{^}}this is duplicate
+
+; RUN: FileCheck %s --input-file %s --check-prefix=CHECK-CNT4
+CHECK-CNT4-COUNT-5: this is duplicate
+CHECK-CNT4-EMPTY:
+
+Many-label:
+
+-many-
+-many-
+-many-
+-many-
+-many-
+-many-
+-many-
+-many-
+-many-
+-many-
+-many-
+-many-
+-many-
+-many-
+-many-
+-many-
+
+; RUN: FileCheck %s --input-file %s --check-prefix=CHECK-CNTMANY
+CHECK-CNTMANY-COUNT-2: this is duplicate
+CHECK-CNTMANY-LABEL: Many-label:
+CHECK-CNTMANY-EMPTY:
+CHECK-CNTMANY-COUNT-16: {{^}}-many-
+CHECK-CNTMANY-EMPTY:
+
+;
+; Tests on mismatches:
+;
+
+; RUN: not FileCheck %s --input-file %s --check-prefix=CHECK-MIS1 2>&1 | FileCheck %s --check-prefix=MISCOUNT1
+CHECK-MIS1-COUNT-3: this is duplicate
+CHECK-MIS1: {{^}}this is not duplicate
+MISCOUNT1: [[@LINE-1]]:13: error: CHECK-MIS1: expected string not found in input
+
+; RUN: not FileCheck %s --input-file %s --check-prefix=CHECK-MIS2 2>&1 | FileCheck %s --check-prefix=MISCOUNT2
+CHECK-MIS2-COUNT-10: {{^this is duplicate}}
+CHECK-MIS2: {{^}}this is not duplicate
+MISCOUNT2: [[@LINE-2]]:22: error: CHECK-MIS2-COUNT: expected string not found in input
+
+; RUN: not FileCheck %s --input-file %s --check-prefix=CHECK-MIS3 2>&1 | FileCheck %s --check-prefix=MISCOUNT3
+CHECK-MIS3-COUNT-5: this is duplicate
+CHECK-MIS3-EMPTY:
+CHECK-MIS3-LABEL: Many-label:
+CHECK-MIS3-EMPTY:
+CHECK-MIS3-COUNT-160: {{^}}-many-
+CHECK-MIS3-EMPTY:
+MISCOUNT3: [[@LINE-2]]:23: error: CHECK-MIS3-COUNT: expected string not found in input (17 out of 160)