[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

451–453

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

103

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 that are undefined.
+void stripIFSUndefinedSymbols(IFSStub &Stub);
+
 /// 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::stripIFSUndefinedSymbols(IFSStub &Stub) {
+  for (auto Iter = Stub.Symbols.begin(); Iter != Stub.Symbols.end();) {
+    if (Iter->Undefined) {
+      Iter = Stub.Symbols.erase(Iter);
+    } else {
+      Iter++;
+    }
+  }
+}

llvm/test/tools/llvm-ifs/strip-undefined-symbols.test

+# RUN: llvm-ifs --input-format=ELF --strip-undefined --output-format=IFS --output=- %p/Inputs/gnu_hash.so | FileCheck %s
+
+# CHECK:      --- !ifs-v1
+# CHECK-NEXT: IfsVersion:      3.0
+# CHECK-NEXT: SoName:          libsomething.so
+# CHECK-NEXT: Target: { ObjectFormat: ELF, Arch: x86_64, Endianness: little, BitWidth: 64 }
+# CHECK-NEXT: NeededLibs:
+# CHECK-NEXT:   - libm.so.6
+# CHECK-NEXT:   - libc.so.6
+# CHECK-NEXT:   - ld-linux-x86-64.so.2
+# CHECK-NEXT: Symbols:
+# CHECK-NEXT:   - { Name: AGlobalInteger, Type: Object, Size: 4 }
+# CHECK-NEXT:   - { Name: AThreadLocalLongInteger, Type: TLS, Size: 8 }
+# CHECK-NEXT:   - { Name: _Z11rotateArrayPii, Type: Func }
+# CHECK-NEXT:   - { Name: _fini, Type: Func }
+# CHECK-NEXT:   - { Name: _init, Type: Func }
+# CHECK-NEXT: ...

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

 cl::opt<bool> StripIFSEndiannessWidth(
     "strip-ifs-endianness",
     cl::desc("Strip target endianness information away from IFS output"),
     cl::cat(IfsCategory));
 cl::opt<bool> StripIFSTarget(
     "strip-ifs-target",
     cl::desc("Strip all target information away from IFS output"),
     cl::cat(IfsCategory));
+cl::opt<bool>
+    StripUndefined("strip-undefined",
+                   cl::desc("Strip undefined symbols from IFS output"),
+                   cl::cat(IfsCategory));
+
 cl::opt<std::string>
     SoName("soname",
            cl::desc("Manually set the DT_SONAME entry of any emitted files"),
            cl::value_desc("name"), cl::cat(IfsCategory));
 cl::opt<std::string> OutputFilePath("output", cl::desc("Output file"),
                                     cl::cat(IfsCategory));
 cl::alias OutputFilePathA("o", cl::desc("Alias for --output"),
                           cl::aliasopt(OutputFilePath), cl::cat(IfsCategory));
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 (StripUndefined)
+      stripIFSUndefinedSymbols(Stub);
     Error IFSWriteError = writeIFS(OutputFilePath.getValue(), Stub);
     if (IFSWriteError)
       fatalError(std::move(IFSWriteError));
     break;
   }
   case FileFormat::ELF: {
     Error TargetError = validateIFSTarget(Stub, true);
     if (TargetError)
       fatalError(std::move(TargetError));