[lld-macho] Don't sort map file entries by name

[int3]

Summary

ld64 emits them in address order but not in alphabetical order. This
sorting is particularly expensive for dead-stripped symbols (which don't
need to be sorted at all, unlike live symbols that need to be sorted by
address).

Timings for chromium_framework_less_dwarf (with the -map flag added to
the response file) on my 16-core Mac Pro:

           base           diff           difference (95% CI)
sys_time   1.997 ± 0.038  2.004 ± 0.028  [  -0.6% ..   +1.3%]
user_time  8.698 ± 0.085  8.167 ± 0.070  [  -6.6% ..   -5.6%]
wall_time  7.965 ± 0.114  7.715 ± 0.347  [  -5.1% ..   -1.2%]
samples    25             23

[thakis]

Test failure on windows on presubmit testing looks like it might be real.

[int3]

update test

[thakis]

lg

lld/MachO/MapFile.cpp

if (isa<ObjFile>(file) || isa<BitcodeFile>(file)) {
             }
             hasEmittedSymbol = true;
           }
       }
       if (hasEmittedSymbol)
         info.files.push_back(file);
     }
   parallelSort(info.liveSymbols.begin(), info.liveSymbols.end(),
-               [](Defined *a, Defined *b) {
-                 return a->getVA() != b->getVA() ? a->getVA() < b->getVA()
-                                                 : a->getName() < b->getName();
-               });
-  parallelSort(
-      info.deadSymbols.begin(), info.deadSymbols.end(),
-      [](Defined *a, Defined *b) { return a->getName() < b->getName(); });
+               [](Defined *a, Defined *b) { return a->getVA() < b->getVA(); });
   return info;
 }
 
 // Construct a map from symbols to their stringified representations.
 // Demangling symbols (which is what toString() does) is slow, so
 // we do that in batch using parallel-for.
 static DenseMap<Symbol *, std::string>
 getSymbolStrings(ArrayRef<Defined *> syms) {

lld/test/MachO/dead-strip.s

 # EXECDATA-LABEL: Exports trie:
 # EXECDATA-DAG:   _ref_com
 # EXECDATA-DAG:   _no_dead_strip_globl
 # EXECDATA-DAG:   __mh_execute_header
 
 ## Check that dead stripped symbols get listed properly.
 # RUN: FileCheck --check-prefix=MAP %s < %t/map
 
-# MAP: _main
+# MAP:        _main
 # MAP-LABEL: Dead Stripped Symbols
-# MAP: <<dead>> 0x00000001 [ 1] _unref_com
-# MAP: <<dead>> 0x00000008 [ 1] _unref_data
-# MAP: <<dead>> 0x00000006 [ 1] _unref_extern
-# MAP: <<dead>> 0x00000001 [ 1] _unref_local
-# MAP: <<dead>> 0x00000007 [ 1] _unref_private_extern
-# MAP: <<dead>> 0x00000008 [ 1] l_unref_data
+# MAP-DAG:   <<dead>> 0x00000001 [ 1] _unref_com
+# MAP-DAG:   <<dead>> 0x00000008 [ 1] _unref_data
+# MAP-DAG:   <<dead>> 0x00000006 [ 1] _unref_extern
+# MAP-DAG:   <<dead>> 0x00000001 [ 1] _unref_local
+# MAP-DAG:   <<dead>> 0x00000007 [ 1] _unref_private_extern
+# MAP-DAG:   <<dead>> 0x00000008 [ 1] l_unref_data
 
 ## Run dead stripping on code without any dead symbols.
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
 # RUN:     %t/no-dead-symbols.s -o %t/no-dead-symbols.o
 # RUN: %lld -lSystem -dead_strip -map %t/no-dead-symbols-map \
 # RUN:     %t/no-dead-symbols.o -o %t/no-dead-symbols
 ## Mark the end of the file with a string.
 # RUN: FileCheck --check-prefix=NODEADSYMBOLS %s < %t/no-dead-symbols-map