[ifs] Add --strip-needed flag

Reviewed By: haowei, mcgrathr

Differential Revision: https://reviews.llvm.org/D119907

llvm/test/tools/llvm-ifs/strip-needed.test

@@ -0,0 +1,26 @@
+## Test --strip-needed flag
+
+# RUN: llvm-ifs --input-format=IFS --strip-needed --output-ifs=- %s | FileCheck %s
+
+# RUN: llvm-ifs --input-format=IFS --output-elf=- %s | \
+# RUN: obj2yaml | FileCheck %s --check-prefix=FROM-ELF
+
+# RUN: llvm-ifs --input-format=IFS --strip-needed --output-elf=- %s | \
+# RUN: obj2yaml | FileCheck %s --check-prefix=FROM-ELF-STRIP-NEEDED
+
+--- !ifs-v1
+IfsVersion: 3.0
+Target: { ObjectFormat: ELF, Arch: AArch64, Endianness: little, BitWidth: 64 }
+NeededLibs:
+  - ''
+Symbols: []
+...
+
+# CHECK:      --- !ifs-v1
+# CHECK-NEXT: IfsVersion: {{[1-9]\d*\.(0|([1-9]\d*))}}
+# CHECK-NEXT: Target: { ObjectFormat: ELF, Arch: AArch64, Endianness: little, BitWidth: 64 }
+# CHECK-NEXT: Symbols: []
+# CHECK-NEXT: ...
+
+# FROM-ELF: DT_NEEDED
+# FROM-ELF-STRIP-NEEDED-NOT: DT_NEEDED

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

@@ -103,6 +103,9 @@ cl::opt<bool>
     StripUndefined("strip-undefined",
                    cl::desc("Strip undefined symbols from IFS output"),
                    cl::cat(IfsCategory));
+cl::opt<bool> StripNeededLibs("strip-needed",
+                              cl::desc("Strip needed libs from output"),
+                              cl::cat(IfsCategory));
 
 cl::opt<std::string>
     SoName("soname",
@@ -417,6 +420,9 @@ int main(int argc, char *argv[]) {
   if (OverrideError)
     fatalError(std::move(OverrideError));
 
+  if (StripNeededLibs)
+    Stub.NeededLibs.clear();
+
   if (OutputELFFilePath.getNumOccurrences() == 0 &&
       OutputIFSFilePath.getNumOccurrences() == 0 &&
       OutputTBDFilePath.getNumOccurrences() == 0) {