[lld] 1d1aa2d - [lld-macho] Mark aliased symbols as noDeadStrip

[Keith Smiley via llvm-commits]

Author: Keith Smiley
Date: 2022-10-04T14:53:53-07:00
New Revision: 1d1aa2d0130ce5683514330c876464bfd754dec3

URL: https://github.com/llvm/llvm-project/commit/1d1aa2d0130ce5683514330c876464bfd754dec3
DIFF: https://github.com/llvm/llvm-project/commit/1d1aa2d0130ce5683514330c876464bfd754dec3.diff

LOG: [lld-macho] Mark aliased symbols as noDeadStrip

This matches ld64 behavior

Differential Revision: https://reviews.llvm.org/D135082

Added: 
    

Modified: 
    lld/MachO/Driver.cpp
    lld/MachO/MarkLive.cpp
    lld/test/MachO/alias-option.s

Removed: 
    


################################################################################
diff  --git a/lld/MachO/Driver.cpp b/lld/MachO/Driver.cpp
index febeace99d3a..a1a491c4a819 100644
--- a/lld/MachO/Driver.cpp
+++ b/lld/MachO/Driver.cpp
@@ -1241,7 +1241,8 @@ static void createAliases() {
   for (const auto &pair : config->aliasedSymbols) {
     if (const auto &sym = symtab->find(pair.first)) {
       if (const auto &defined = dyn_cast<Defined>(sym)) {
-        symtab->aliasDefined(defined, pair.second, defined->getFile());
+        symtab->aliasDefined(defined, pair.second, defined->getFile())
+            ->noDeadStrip = true;
       } else {
         error("TODO: support aliasing to symbols of kind " +
               Twine(sym->kind()));

diff  --git a/lld/MachO/MarkLive.cpp b/lld/MachO/MarkLive.cpp
index d407599ee810..2ad85c62d047 100644
--- a/lld/MachO/MarkLive.cpp
+++ b/lld/MachO/MarkLive.cpp
@@ -229,7 +229,7 @@ void markLive() {
       // FIXME: When we implement these flags, make symbols from them GC
       // roots:
       // * -reexported_symbol(s_list)
-      // * -alias(-list)
+      // * -alias_list
       // * -init
 
       // In dylibs and bundles and in executables with -export_dynamic,

diff  --git a/lld/test/MachO/alias-option.s b/lld/test/MachO/alias-option.s
index dd366e78bc5f..087a5e021b8f 100644
--- a/lld/test/MachO/alias-option.s
+++ b/lld/test/MachO/alias-option.s
@@ -21,7 +21,9 @@
 # MAIN: [[#%x,FOO_ADDR:]] T _foo
 # MAIN: [[#FOO_ADDR]]     T _main
 
-# RUN: %lld -alias _foo _bar -alias _main _fake_main %t/main.o %t/foo.o -o %t/multiple.o
+## Verify dead stripping doesn't remove the aliased symbol. This behavior 
diff ers
+## from ld64 where it actually does dead strip only the alias, not the original symbol.
+# RUN: %lld -dead_strip -alias _foo _bar -alias _main _fake_main %t/main.o %t/foo.o -o %t/multiple.o
 # RUN: llvm-nm %t/multiple.o | FileCheck %s --check-prefix=MULTIPLE
 
 # MULTIPLE: [[#%x,FOO_ADDR:]]  T _bar
@@ -30,11 +32,13 @@
 # MULTIPLE: [[#MAIN_ADDR]]     T _main
 
 #--- foo.s
+.subsections_via_symbols
 .globl _foo
 _foo:
   ret
 
 #--- main.s
+.subsections_via_symbols
 .globl _main
 _main:
   ret