[FileCheck] Report missing prefixes when more than one is provided.

If more than a prefix is provided - e.g. --check-prefixes=CHECK,FOO - we
don't report if (say) FOO is never used. This may lead to a gap in our
test coverage.

This patch introduces a new option, --allow-unused-prefixes. It
currently is set to true, keeping today's behavior. After we explicitly
set it in tests where this behavior was actually intentional, we will
switch it to false by default.

Differential Revision: https://reviews.llvm.org/D90281

1 files changed, 16 insertions, 8 deletions

diff --git a/llvm/lib/FileCheck/FileCheck.cpp b/llvm/lib/FileCheck/FileCheck.cpp
index a0371cf..8e234b2 100644
--- a/llvm/lib/FileCheck/FileCheck.cpp
+++ b/llvm/lib/FileCheck/FileCheck.cpp
@@ -22,6 +22,7 @@
 #include "llvm/Support/FormatVariadic.h"
 #include <cstdint>
 #include <list>
+#include <set>
 #include <tuple>
 #include <utility>
 
@@ -1825,8 +1826,10 @@ bool FileCheck::readCheckFile(
   // found.
   unsigned LineNumber = 1;
 
-  bool FoundUsedCheckPrefix = false;
-  while (1) {
+  std::set<StringRef> PrefixesNotFound(Req.CheckPrefixes.begin(),
+                                       Req.CheckPrefixes.end());
+  const size_t DistinctPrefixes = PrefixesNotFound.size();
+  while (true) {
     Check::FileCheckType CheckTy;
 
     // See if a prefix occurs in the memory buffer.
@@ -1837,7 +1840,7 @@ bool FileCheck::readCheckFile(
     if (UsedPrefix.empty())
       break;
     if (CheckTy != Check::CheckComment)
-      FoundUsedCheckPrefix = true;
+      PrefixesNotFound.erase(UsedPrefix);
 
     assert(UsedPrefix.data() == Buffer.data() &&
            "Failed to move Buffer's start forward, or pointed prefix outside "
@@ -1930,14 +1933,19 @@ bool FileCheck::readCheckFile(
 
   // When there are no used prefixes we report an error except in the case that
   // no prefix is specified explicitly but -implicit-check-not is specified.
-  if (!FoundUsedCheckPrefix &&
+  const bool NoPrefixesFound = PrefixesNotFound.size() == DistinctPrefixes;
+  const bool SomePrefixesUnexpectedlyNotUsed =
+      !Req.AllowUnusedPrefixes && !PrefixesNotFound.empty();
+  if ((NoPrefixesFound || SomePrefixesUnexpectedlyNotUsed) &&
       (ImplicitNegativeChecks.empty() || !Req.IsDefaultCheckPrefix)) {
     errs() << "error: no check strings found with prefix"
-           << (Req.CheckPrefixes.size() > 1 ? "es " : " ");
-    for (size_t I = 0, E = Req.CheckPrefixes.size(); I != E; ++I) {
-      if (I != 0)
+           << (PrefixesNotFound.size() > 1 ? "es " : " ");
+    bool First = true;
+    for (StringRef MissingPrefix : PrefixesNotFound) {
+      if (!First)
         errs() << ", ";
-      errs() << "\'" << Req.CheckPrefixes[I] << ":'";
+      errs() << "\'" << MissingPrefix << ":'";
+      First = false;
     }
     errs() << '\n';
     return true;