Change llvm-nm for Mach-O files to use dyld info in some cases when printing symbols.

In order to reduce swift binary sizes, Apple is now stripping swift symbols
from the nlist symbol table.  llvm-nm currently only looks at the nlist symbol
table and misses symbols that are present in dyld info.   This makes it hard to
know the set of symbols for a binary using just llvm-nm.  Unless you know to
run llvm-objdump -exports-trie that can output the exported symbols in the dyld
info from the export trie, which does so but in a different format.

Also moving forward the time may come a when a fully linked Mach-O file that
uses dyld will no longer have an nlist symbol table to avoid duplicating the
symbol information.

This change adds three flags to llvm-nm, -add-dyldinfo, -no-dyldinfo, and
-dyldinfo-only.

The first, -add-dyldinfo, has the same effect as when the new bit in the Mach-O
header, MH_NLIST_OUTOFSYNC_WITH_DYLDINFO, appears in a binary.  In that it
looks through the dyld info from the export trie and adds symbols to be printed
that are not already in its internal SymbolList variable.  The -no-dyldinfo
option turns this behavior off.

The -dyldinfo-only option only looks at the dyld information and recreates the
symbol table from the dyld info from the export trie and binding information.
As if it the Mach-O file had no nlist symbol table.

Also fixed a few bugs with Mach-O N_INDR symbols not correctly printing the
indirect name, or in the same format as the old nm-classic program.

rdar://32021551

llvm-svn: 305733

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/tools/llvm-objdump/MachODump.cpp b/llvm/tools/llvm-objdump/MachODump.cpp
index 8927f57..40b5e25 100644
--- a/llvm/tools/llvm-objdump/MachODump.cpp
+++ b/llvm/tools/llvm-objdump/MachODump.cpp
@@ -7634,6 +7634,10 @@ static void PrintMachHeader(uint32_t magic, uint32_t cputype,
       outs() << " APP_EXTENSION_SAFE";
       f &= ~MachO::MH_APP_EXTENSION_SAFE;
     }
+    if (f & MachO::MH_NLIST_OUTOFSYNC_WITH_DYLDINFO) {
+      outs() << " NLIST_OUTOFSYNC_WITH_DYLDINFO";
+      f &= ~MachO::MH_NLIST_OUTOFSYNC_WITH_DYLDINFO;
+    }
     if (f != 0 || flags == 0)
       outs() << format(" 0x%08" PRIx32, f);
   } else {