[ThinLTO] Subsume all importing checks into a single flag

Summary:
This adds a new summary flag NotEligibleToImport that subsumes
several existing flags (NoRename, HasInlineAsmMaybeReferencingInternal
and IsNotViableToInline). It also subsumes the checking of references
on the summary that was being done during the thin link by
eligibleForImport() for each candidate. It is much more efficient to
do that checking once during the per-module summary build and record
it in the summary.

Reviewers: mehdi_amini

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D28169

llvm-svn: 291108

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -801,12 +801,8 @@ static GlobalValueSummary::GVFlags getDecodedGVSummaryFlags(uint64_t RawFlags,
   // to getDecodedLinkage() will need to be taken into account here as above.
   auto Linkage = GlobalValue::LinkageTypes(RawFlags & 0xF); // 4 bits
   RawFlags = RawFlags >> 4;
-  bool NoRename = RawFlags & 0x1;
-  bool IsNotViableToInline = RawFlags & 0x2;
-  bool HasInlineAsmMaybeReferencingInternal = RawFlags & 0x4;
-  return GlobalValueSummary::GVFlags(Linkage, NoRename,
-                                     HasInlineAsmMaybeReferencingInternal,
-                                     IsNotViableToInline);
+  bool NotEligibleToImport = (RawFlags & 0x1) || Version < 3;
+  return GlobalValueSummary::GVFlags(Linkage, NotEligibleToImport);
 }
 
 static GlobalValue::VisibilityTypes getDecodedVisibility(unsigned Val) {
@@ -4838,9 +4834,9 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(
   }
   const uint64_t Version = Record[0];
   const bool IsOldProfileFormat = Version == 1;
-  if (!IsOldProfileFormat && Version != 2)
+  if (Version < 1 || Version > 3)
     return error("Invalid summary version " + Twine(Version) +
-                 ", 1 or 2 expected");
+                 ", 1, 2 or 3 expected");
   Record.clear();
 
   // Keep around the last seen summary to be used when we see an optional