[llvm-strip] Expose --strip-unneeded option

Differential Revision: https://reviews.llvm.org/D47818

llvm-svn: 334182

llvm/test/tools/llvm-objcopy/strip-unneeded.test

@@ -1,7 +1,14 @@
 # RUN: yaml2obj %s > %t
+# RUN: cp %t %t1
 # RUN: llvm-objcopy --strip-unneeded %t %t2
+# Verify that llvm-objcopy has not modified the input.
+# RUN: cmp %t %t1
 # RUN: llvm-readobj -symbols %t2 | FileCheck %s
 
+# Verify that llvm-strip modifies the symbol table the same way.
+# RUN: llvm-strip --strip-unneeded %t
+# RUN: cmp %t %t2
+
 !ELF
 FileHeader:
   Class:           ELFCLASS64

llvm/tools/llvm-objcopy/StripOpts.td

@@ -41,3 +41,6 @@ def discard_all : Flag<["-", "--"], "discard-all">,
                   HelpText<"Remove all local symbols except file and section symbols">;
 def x : Flag<["-"], "x">,
         Alias<discard_all>;
+
+def strip_unneeded : Flag<["-", "--"], "strip-unneeded">,
+                      HelpText<"Remove all symbols not needed by relocations">;

llvm/tools/llvm-objcopy/llvm-objcopy.cpp

@@ -583,12 +583,12 @@ CopyConfig ParseStripOptions(ArrayRef<const char *> ArgsArr) {
   Config.OutputFilename =
       InputArgs.getLastArgValue(STRIP_output, Positional[0]);
 
-  // Strip debug info only.
   Config.StripDebug = InputArgs.hasArg(STRIP_strip_debug);
   
   Config.DiscardAll = InputArgs.hasArg(STRIP_discard_all);
-  
-  if (!Config.StripDebug && !Config.DiscardAll)
+  Config.StripUnneeded = InputArgs.hasArg(STRIP_strip_unneeded);
+
+  if (!Config.StripDebug && !Config.StripUnneeded && !Config.DiscardAll)
     Config.StripAll = true;
 
   for (auto Arg : InputArgs.filtered(STRIP_remove_section))