[ifs] Add option to hide undefined symbols

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

Differential Revision: https://reviews.llvm.org/D108428

llvm/include/llvm/InterfaceStub/IFSHandler.h

@@ -51,6 +51,9 @@ Error validateIFSTarget(IFSStub &Stub, bool ParseTriple);
 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);
 

llvm/lib/InterfaceStub/IFSHandler.cpp

@@ -327,3 +327,13 @@ void ifs::stripIFSTarget(IFSStub &Stub, bool StripTriple, bool StripArch,
     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

@@ -0,0 +1,17 @@
+# 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

@@ -99,6 +99,11 @@ 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"),
@@ -443,6 +448,8 @@ int main(int argc, char *argv[]) {
       stripIFSTarget(Stub, StripIFSTarget, StripIFSArch,
                      StripIFSEndiannessWidth, StripIFSBitWidth);
     }
+    if (StripUndefined)
+      stripIFSUndefinedSymbols(Stub);
     Error IFSWriteError = writeIFS(OutputFilePath.getValue(), Stub);
     if (IFSWriteError)
       fatalError(std::move(IFSWriteError));