[ProfData] Detect if zlib is available

As discussed on [1], if the profile is compressed and llvm-profdata is not built with zlib support, the error message is not informative. Give a better error message if zlib is not available.

[1] http://lists.llvm.org/pipermail/llvm-dev/2017-July/115571.html

Reviewers: davidxl, dblaikie

Differential Revision: https://reviews.llvm.org/D35586

llvm-svn: 308789

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/ProfileData/InstrProf.cpp b/llvm/lib/ProfileData/InstrProf.cpp
index 48c1643cb13..a732bedc6fa 100644
--- a/llvm/lib/ProfileData/InstrProf.cpp
+++ b/llvm/lib/ProfileData/InstrProf.cpp
@@ -111,6 +111,8 @@ static std::string getInstrProfErrString(instrprof_error Err) {
     return "Failed to uncompress data (zlib)";
   case instrprof_error::empty_raw_profile:
     return "Empty raw profile file";
+  case instrprof_error::zlib_unavailable:
+    return "Profile uses zlib compression but the profile reader was built without zlib support";
   }
   llvm_unreachable("A value of instrprof_error has no message.");
 }
@@ -430,6 +432,9 @@ Error readPGOFuncNameStrings(StringRef NameStrings, InstrProfSymtab &Symtab) {
     SmallString<128> UncompressedNameStrings;
     StringRef NameStrings;
     if (isCompressed) {
+      if (!llvm::zlib::isAvailable())
+        return make_error<InstrProfError>(instrprof_error::zlib_unavailable);
+
       StringRef CompressedNameStrings(reinterpret_cast<const char *>(P),
                                       CompressedSize);
       if (Error E =