[MachO] Preserve weak linkage for aliases#198148
Open
syhhyl wants to merge 1 commit into
Open
Conversation
llvmorg-github-actions
Bot
added
backend:AArch64
llvm:codegen
llvm:mc
|
@llvm/pr-subscribers-llvm-mc Author: syhhyl (syhhyl) ChangesMach-O aliases with weak or linkonce linkage were emitted as weak references, which is appropriate for undefined references but not for alias definitions. Emit Mach-O aliases through the same linkage path as other global definitions so weak aliases get .weak_definition. When writing aliased symbols, keep the aliasee flags and include the alias symbol's own flags so N_WEAK_DEF is preserved in the Mach-O n_desc field. Fixes #196047 Full diff: https://github.com/llvm/llvm-project/pull/198148.diff 3 Files Affected:
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 17fd80e81a673..8c3d69ee43200 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -2640,7 +2640,9 @@ void AsmPrinter::emitGlobalAlias(const Module &M, const GlobalAlias &GA) {
return;
}
- if (GA.hasExternalLinkage() || !MAI.getWeakRefDirective())
+ if (MAI.isMachO())
+ emitLinkage(&GA, Name);
+ else 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 b42155d18bf0a..0786ca0e3a83b 100644
--- a/llvm/lib/MC/MachObjectWriter.cpp
+++ b/llvm/lib/MC/MachObjectWriter.cpp
@@ -443,7 +443,10 @@ 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();
- W.write<uint16_t>(Symbol->getEncodedFlags(EncodeAsAltEntry));
+ uint16_t Flags = Symbol->getEncodedFlags(EncodeAsAltEntry);
+ if (IsAlias)
+ Flags |= OrigSymbol.getEncodedFlags(EncodeAsAltEntry);
+ W.write<uint16_t>(Flags);
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
new file mode 100644
index 0000000000000..a936cea618b38
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/macho-weak-alias.ll
@@ -0,0 +1,17 @@
+; 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/pr-subscribers-backend-aarch64 Author: syhhyl (syhhyl) ChangesMach-O aliases with weak or linkonce linkage were emitted as weak references, which is appropriate for undefined references but not for alias definitions. Emit Mach-O aliases through the same linkage path as other global definitions so weak aliases get .weak_definition. When writing aliased symbols, keep the aliasee flags and include the alias symbol's own flags so N_WEAK_DEF is preserved in the Mach-O n_desc field. Fixes #196047 Full diff: https://github.com/llvm/llvm-project/pull/198148.diff 3 Files Affected:
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 17fd80e81a673..8c3d69ee43200 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -2640,7 +2640,9 @@ void AsmPrinter::emitGlobalAlias(const Module &M, const GlobalAlias &GA) {
return;
}
- if (GA.hasExternalLinkage() || !MAI.getWeakRefDirective())
+ if (MAI.isMachO())
+ emitLinkage(&GA, Name);
+ else 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 b42155d18bf0a..0786ca0e3a83b 100644
--- a/llvm/lib/MC/MachObjectWriter.cpp
+++ b/llvm/lib/MC/MachObjectWriter.cpp
@@ -443,7 +443,10 @@ 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();
- W.write<uint16_t>(Symbol->getEncodedFlags(EncodeAsAltEntry));
+ uint16_t Flags = Symbol->getEncodedFlags(EncodeAsAltEntry);
+ if (IsAlias)
+ Flags |= OrigSymbol.getEncodedFlags(EncodeAsAltEntry);
+ W.write<uint16_t>(Flags);
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
new file mode 100644
index 0000000000000..a936cea618b38
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/macho-weak-alias.ll
@@ -0,0 +1,17 @@
+; 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
|
Mach-O aliases with weak or linkonce linkage were emitted as weak references, which is appropriate for undefined references but not for alias definitions. Emit Mach-O aliases through the same linkage path as other global definitions so weak aliases get .weak_definition. When writing aliased symbols, keep the aliasee flags and include the alias symbol's own flags so N_WEAK_DEF is preserved in the Mach-O n_desc field. Fixes llvm#196047
syhhyl
force-pushed
the
fix-196047-macho-weak-alias
branch
from
66f1d94 to
0577ea0
Compare
|
This also appears to fix #111321. |
Contributor
|
Bumping this for reviewers as this is a quite important fix 🙌 |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Mach-O aliases with weak or linkonce linkage were emitted as weak references, which is appropriate for undefined references but not for alias definitions. Emit Mach-O aliases through the same linkage path as other global definitions so weak aliases get .weak_definition.
When writing aliased symbols, keep the aliasee flags and include the alias symbol's own flags so N_WEAK_DEF is preserved in the Mach-O n_desc field.
Fixes #196047 #111321