[llvm-strip] Expose --discard-all option

Expose objcopy's --discard-all option in llvm-strip.

Test plan: make check-all

Differential revision: https://reviews.llvm.org/D47750

llvm-svn: 334131

llvm/test/tools/llvm-objcopy/discard-all.test

@@ -1,8 +1,23 @@
 # RUN: yaml2obj %s > %t
+# RUN: cp %t %t1
 # RUN: llvm-objcopy --discard-all %t %t2
-# RUN: llvm-objcopy -x %t %t3
+# Verify that llvm-objcopy has not modified the input.
+# RUN: cmp %t %t1
 # RUN: llvm-readobj -symbols %t2 | FileCheck %s
-# RUN: diff %t2 %t3
+
+# RUN: llvm-objcopy -x %t %t3
+# Verify that llvm-objcopy has not modified the input.
+# RUN: cmp %t %t1
+# RUN: cmp %t2 %t3
+
+# Verify that llvm-strip modifies the symbol table the same way.
+
+# RUN: cp %t %t4
+# RUN: llvm-strip --discard-all %t4
+# RUN: cmp %t2 %t4
+
+# RUN: llvm-strip -x %t
+# RUN: cmp %t2 %t
 
 !ELF
 FileHeader:

llvm/tools/llvm-objcopy/StripOpts.td

@@ -36,3 +36,8 @@ defm keep_symbol : Eq<"keep-symbol">,
 
 def K : JoinedOrSeparate<["-"], "K">,
         Alias<keep_symbol>;
+
+def discard_all : Flag<["-", "--"], "discard-all">,
+                  HelpText<"Remove all local symbols except file and section symbols">;
+def x : Flag<["-"], "x">,
+        Alias<discard_all>;

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

@@ -585,7 +585,10 @@ CopyConfig ParseStripOptions(ArrayRef<const char *> ArgsArr) {
 
   // Strip debug info only.
   Config.StripDebug = InputArgs.hasArg(STRIP_strip_debug);
-  if (!Config.StripDebug)
+  
+  Config.DiscardAll = InputArgs.hasArg(STRIP_discard_all);
+  
+  if (!Config.StripDebug && !Config.DiscardAll)
     Config.StripAll = true;
 
   for (auto Arg : InputArgs.filtered(STRIP_remove_section))