Revert "[MachO] Preserve weak linkage for aliases"

[cofibrant]

Reverts #198148

As #212001 points out, #198148's approach to merging the linkage flags is incorrect. I propose we revert for now, build an understanding of the work required to support this properly and try again.

[cofibrant]

CC @syhhyl

[llvmorg-github-actions]

@llvm/pr-subscribers-llvm-mc

@llvm/pr-subscribers-backend-aarch64

Author: Nathan Corbyn (cofibrant)

Changes

Reverts llvm/llvm-project#198148

As #212001 points out, #198148's approach to merging the linkage flags is incorrect. I propose we revert for now, build an understanding of the work required to support this properly and try again.

---

Full diff: https://github.com/llvm/llvm-project/pull/212009.diff

3 Files Affected:

• (modified) llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp (+1-3)
• (modified) llvm/lib/MC/MachObjectWriter.cpp (+1-6)
• (removed) llvm/test/CodeGen/AArch64/macho-weak-alias.ll (-17)

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index e544fa4d4414a..11d39fcff0ff7 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -2644,9 +2644,7 @@ void AsmPrinter::emitGlobalAlias(const Module &M, const GlobalAlias &GA) {
     return;
   }
 
-  if (MAI.isMachO())
-    emitLinkage(&GA, Name);
-  else if (GA.hasExternalLinkage() || !MAI.getWeakRefDirective())
+  if (GA.hasExternalLinkage() || !MAI.getWeakRefDirective())
     OutStreamer->emitSymbolAttribute(Name, MCSA_Global);
   else if (GA.hasWeakLinkage() || GA.hasLinkOnceLinkage())
     OutStreamer->emitSymbolAttribute(Name, MCSA_WeakReference);
diff --git a/llvm/lib/MC/MachObjectWriter.cpp b/llvm/lib/MC/MachObjectWriter.cpp
index 657f6f40fd9e9..e274d886c22d8 100644
--- a/llvm/lib/MC/MachObjectWriter.cpp
+++ b/llvm/lib/MC/MachObjectWriter.cpp
@@ -443,12 +443,7 @@ void MachObjectWriter::writeNlist(MachSymbolData &MSD, const MCAssembler &Asm) {
   // The Mach-O streamer uses the lowest 16-bits of the flags for the 'desc'
   // value.
   bool EncodeAsAltEntry = IsAlias && OrigSymbol.isAltEntry();
-  uint16_t Flags = Symbol->getEncodedFlags(EncodeAsAltEntry);
-  // Preserve the aliasee's flags while adding alias-specific flags,
-  // such as N_WEAK_DEF emitted by .weak_definition.
-  if (IsAlias)
-    Flags |= OrigSymbol.getEncodedFlags(EncodeAsAltEntry);
-  W.write<uint16_t>(Flags);
+  W.write<uint16_t>(Symbol->getEncodedFlags(EncodeAsAltEntry));
   if (is64Bit())
     W.write<uint64_t>(Address);
   else
diff --git a/llvm/test/CodeGen/AArch64/macho-weak-alias.ll b/llvm/test/CodeGen/AArch64/macho-weak-alias.ll
deleted file mode 100644
index a936cea618b38..0000000000000
--- a/llvm/test/CodeGen/AArch64/macho-weak-alias.ll
+++ /dev/null
@@ -1,17 +0,0 @@
-; RUN: llc -mtriple=aarch64-apple-macosx13.0.0 -filetype=obj %s -o %t.o
-; RUN: llvm-nm -m %t.o | FileCheck %s
-
-define internal void @foo_internal() {
-  ret void
-}
-
-@foo_default = weak_odr alias void (), ptr @foo_internal
-@foo_hidden = weak_odr hidden alias void (), ptr @foo_internal
-
-define weak_odr hidden void @foo_defined() {
-  ret void
-}
-
-; CHECK-DAG: weak external _foo_default
-; CHECK-DAG: weak private external _foo_hidden
-; CHECK-DAG: weak private external _foo_defined

[llvm-ci]

LLVM Buildbot has detected a new failure on builder clang-arm64-windows-msvc running on linaro-armv8-windows-msvc-04 while building llvm at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/161/builds/12451

Here is the relevant piece of the build log for the reference

Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: tools/llvm-debuginfod-find/timeout.test' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 3
rm -rf C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\build\test\tools\llvm-debuginfod-find\Output\timeout.test.tmp
# executed command: rm -rf 'C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\build\test\tools\llvm-debuginfod-find\Output\timeout.test.tmp'
# RUN: at line 4
mkdir -p C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\build\test\tools\llvm-debuginfod-find\Output\timeout.test.tmp/debuginfod-cache
# executed command: mkdir -p 'C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\build\test\tools\llvm-debuginfod-find\Output\timeout.test.tmp/debuginfod-cache'
# RUN: at line 7
env DEBUGINFOD_TIMEOUT=1  env DEBUGINFOD_CACHE=C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\build\test\tools\llvm-debuginfod-find\Output\timeout.test.tmp/debuginfod-cache  env DEBUGINFOD_HEADERS_FILE=C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\llvm-project\llvm\test\tools\llvm-debuginfod-find/Inputs/headers    "C:\Users\tcwg\scoop\apps\python\current\python.exe" C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\llvm-project\llvm\test\tools\llvm-debuginfod-find/Inputs/delay_req.py c:\users\tcwg\llvm-worker\clang-arm64-windows-msvc\build\bin\llvm-debuginfod-find.exe --debuginfo 0 | c:\users\tcwg\llvm-worker\clang-arm64-windows-msvc\build\bin\filecheck.exe C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\llvm-project\llvm\test\tools\llvm-debuginfod-find\timeout.test
# executed command: env DEBUGINFOD_TIMEOUT=1 env 'DEBUGINFOD_CACHE=C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\build\test\tools\llvm-debuginfod-find\Output\timeout.test.tmp/debuginfod-cache' env 'DEBUGINFOD_HEADERS_FILE=C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\llvm-project\llvm\test\tools\llvm-debuginfod-find/Inputs/headers' 'C:\Users\tcwg\scoop\apps\python\current\python.exe' 'C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\llvm-project\llvm\test\tools\llvm-debuginfod-find/Inputs/delay_req.py' 'c:\users\tcwg\llvm-worker\clang-arm64-windows-msvc\build\bin\llvm-debuginfod-find.exe' --debuginfo 0
# .---command stderr------------
# | 127.0.0.1 - - [25/Jul/2026 13:09:38] "GET /buildid/00/debuginfo HTTP/1.1" 501 -
# `-----------------------------
# executed command: 'c:\users\tcwg\llvm-worker\clang-arm64-windows-msvc\build\bin\filecheck.exe' 'C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\llvm-project\llvm\test\tools\llvm-debuginfod-find\timeout.test'
# .---command stderr------------
# | C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\llvm-project\llvm\test\tools\llvm-debuginfod-find\timeout.test:13:13: error: CHECK-SAME: expected string not found in input
# | CHECK-SAME: Timeout was reached
# |             ^
# | <stdin>:5:13: note: scanning from here
# | Build ID 00: Failed to receive HTTP response
# |             ^
# | <stdin>:5:14: note: possible intended match here
# | Build ID 00: Failed to receive HTTP response
# |              ^
# | 
# | Input file: <stdin>
# | Check file: C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\llvm-project\llvm\test\tools\llvm-debuginfod-find\timeout.test
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |            1: warning: could not parse debuginfod header: C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\llvm-project\llvm\test\tools\llvm-debuginfod-find/Inputs/headers:3
# |  
# |            2: warning: could not parse debuginfod header: C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\llvm-project\llvm\test\tools\llvm-debuginfod-find/Inputs/headers:4
# |  
# |            3: warning: could not parse debuginfod header: C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\llvm-project\llvm\test\tools\llvm-debuginfod-find/Inputs/headers:5
# |  
# |            4: warning: could not parse debuginfod header: C:\Users\tcwg\llvm-worker\clang-arm64-windows-msvc\llvm-project\llvm\test\tools\llvm-debuginfod-find/Inputs/headers:6
# |  
# |            5: Build ID 00: Failed to receive HTTP response
# |  
# | same:13'0                {                                    search range start (exclusive)
# | same:13'1                                                     error: no match found in search range
# | same:13'2                  ?                                  possible intended match
# |            6:  
...