[ifs] Add option to hide undefined symbols

[haowei]

Summary

This change add an option to llvm-ifs to hide undefined symbols from its output.

[phosek]

Would it be possible to include a test for this option?

llvm/lib/InterfaceStub/IFSHandler.cpp

333–334

I'd use a for loop here.

337

You need to update it since the iterator will be invalidated by the erase operation.

llvm/tools/llvm-ifs/llvm-ifs.cpp

434–436

No need for braces.

[mcgrathr]

llvm/lib/InterfaceStub/IFSHandler.cpp

331

It's not clear why this function takes the various arguments since it has only one call site that uses fixed values.

337

it = erase(it); should work.

[haowei]

I forgot to attach the test into git in the previous commit. They were attached int this change.

llvm/lib/InterfaceStub/IFSHandler.cpp

331

I was plan to make it generic so next time if we need to strip any more symbols based on a different metric, I don't need to write a new function. But I think it does not really matter since it is quite simple.

[haowei]

Rebase to latest HEAD

[phosek]

llvm/tools/llvm-ifs/llvm-ifs.cpp

91

Small suggestion, I'd call this just strip-undefined, the symbol part is already implied and it better matches spelling used by tools like llvm-objcopy.

[phosek]

LGTM

llvm/include/llvm/InterfaceStub/IFSHandler.h

 
 /// Validate the target platform inforation in the text stub.
 Error validateIFSTarget(IFSStub &Stub, bool ParseTriple);
 
 /// Strips target platform information from the text stub.
 void stripIFSTarget(IFSStub &Stub, bool StripTriple, bool StripArch,
                     bool StripEndianness, bool StripBitWidth);
 
+/// Strips symbols from IFS symbol table based on the type and attributes.
+void stripIFSSymbols(IFSStub &Stub, IFSSymbolType Type, bool Undefined,
+                     bool Weak);
+
 /// Parse llvm triple string into a IFSTarget struct.
 IFSTarget parseTriple(StringRef TripleStr);
 
 } // end namespace ifs
 } // end namespace llvm
 
 #endif // LLVM_INTERFACESTUB_IFSHANDLER_H

llvm/lib/InterfaceStub/IFSHandler.cpp

void ifs::stripIFSTarget(IFSStub &Stub, bool StripTriple, bool StripArch,
   }
   if (StripTriple) {
     Stub.Target.Triple.reset();
   }
   if (!Stub.Target.Arch && !Stub.Target.BitWidth && !Stub.Target.Endianness) {
     Stub.Target.ObjectFormat.reset();
   }
 }
+
+void ifs::stripIFSSymbols(IFSStub &Stub, IFSSymbolType Type, bool Undefined,
+                          bool Weak) {
+  std::vector<IFSSymbol>::iterator it = Stub.Symbols.begin();
+  while (it != Stub.Symbols.end()) {
+    if ((Type != IFSSymbolType::Unknown && Type == it->Type) ||
+        (Undefined && it->Undefined) || (Weak && it->Weak)) {
+      Stub.Symbols.erase(it);
+    } else {
+      it++;
+    }
+  }
+}

llvm/tools/llvm-ifs/llvm-ifs.cpp

cl::opt<bool> StripIFSBitWidth(
     "strip-ifs-bitwidth",
     cl::desc("Strip target bit width information away from IFS output"));
 cl::opt<bool> StripIFSEndiannessWidth(
     "strip-ifs-endianness",
     cl::desc("Strip target endianness information away from IFS output"));
 cl::opt<bool> StripIFSTarget(
     "strip-ifs-target",
     cl::desc("Strip all target information away from IFS output"));
+cl::opt<bool>
+    StripUndefinedSymbol("strip-undefined-symbol",
+                         cl::desc("Strip undefined symbols from IFS output"));
 cl::opt<std::string>
     SoName("soname",
            cl::desc("Manually set the DT_SONAME entry of any emitted files"),
            cl::value_desc("name"));
 cl::opt<std::string> OutputFilePath("output", cl::desc("Output file"));
 cl::alias OutputFilePathA("o", cl::desc("Alias for --output"),
                           cl::aliasopt(OutputFilePath));
 cl::opt<bool> WriteIfChanged(
if (InputFormat.getValue() == FileFormat::ELF &&
             "Triple hint does not match the actual bit width", HintEC));
 
       stripIFSTarget(Stub, true, false, false, false);
       Stub.Target.Triple = OptTargetTripleHint.getValue();
     } else {
       stripIFSTarget(Stub, StripIFSTarget, StripIFSArch,
                      StripIFSEndiannessWidth, StripIFSBitWidth);
     }
+    if (StripUndefinedSymbol) {
+      stripIFSSymbols(Stub, IFSSymbolType::Unknown, true, false);
+    }
     Error IFSWriteError = writeIFS(OutputFilePath.getValue(), Stub);
     if (IFSWriteError)
       fatalError(std::move(IFSWriteError));
     break;
   }
   case FileFormat::ELF: {
     Error TargetError = validateIFSTarget(Stub, true);
     if (TargetError)