[llvm] 7198bac - [COFF] Add MC support for emitting IMAGE_WEAK_EXTERN_ANTI_DEPENDENCY symbols
Eli Friedman via llvm-commits
llvm-commits at lists.llvm.org
Wed Jun 7 11:19:09 PDT 2023
Author: Eli Friedman
Date: 2023-06-07T11:07:21-07:00
New Revision: 7198baccdae10d2b23ea3c21b3c09a59ec053ec9
URL: https://github.com/llvm/llvm-project/commit/7198baccdae10d2b23ea3c21b3c09a59ec053ec9
DIFF: https://github.com/llvm/llvm-project/commit/7198baccdae10d2b23ea3c21b3c09a59ec053ec9.diff
LOG: [COFF] Add MC support for emitting IMAGE_WEAK_EXTERN_ANTI_DEPENDENCY symbols
This is mostly useful for ARM64EC, which uses such symbols extensively.
One interesting quirk of ARM64EC is that we need to be able to emit weak
symbols that point at each other (so if either symbol is defined
elsewhere, both symbols point at the definition). This handling is
currently restricted to weak_anti_dep symbols, because we depend on the
current behavior of resolving weak symbols in some cases.
Differential Revision: https://reviews.llvm.org/D145208
Added:
llvm/test/MC/COFF/weak-anti-dep.s
Modified:
llvm/include/llvm/MC/MCDirectives.h
llvm/include/llvm/MC/MCSymbol.h
llvm/include/llvm/MC/MCSymbolCOFF.h
llvm/lib/MC/MCAsmStreamer.cpp
llvm/lib/MC/MCELFStreamer.cpp
llvm/lib/MC/MCExpr.cpp
llvm/lib/MC/MCMachOStreamer.cpp
llvm/lib/MC/MCParser/AsmParser.cpp
llvm/lib/MC/MCParser/COFFAsmParser.cpp
llvm/lib/MC/MCWinCOFFStreamer.cpp
llvm/lib/MC/WinCOFFObjectWriter.cpp
llvm/test/MC/COFF/addrsig.s
Removed:
################################################################################
diff --git a/llvm/include/llvm/MC/MCDirectives.h b/llvm/include/llvm/MC/MCDirectives.h
index b9668a0c994fa..fcab56ff0a740 100644
--- a/llvm/include/llvm/MC/MCDirectives.h
+++ b/llvm/include/llvm/MC/MCDirectives.h
@@ -46,6 +46,7 @@ enum MCSymbolAttr {
MCSA_WeakDefinition, ///< .weak_definition (MachO)
MCSA_WeakReference, ///< .weak_reference (MachO)
MCSA_WeakDefAutoPrivate, ///< .weak_def_can_be_hidden (MachO)
+ MCSA_WeakAntiDep, ///< .weak_anti_dep (COFF)
MCSA_Memtag, ///< .memtag (ELF)
};
diff --git a/llvm/include/llvm/MC/MCSymbol.h b/llvm/include/llvm/MC/MCSymbol.h
index c1fad4481c190..d0d51f32e9677 100644
--- a/llvm/include/llvm/MC/MCSymbol.h
+++ b/llvm/include/llvm/MC/MCSymbol.h
@@ -102,6 +102,9 @@ class MCSymbol {
/// This symbol is private extern.
mutable unsigned IsPrivateExtern : 1;
+ /// This symbol is weak external.
+ mutable unsigned IsWeakExternal : 1;
+
/// LLVM RTTI discriminator. This is actually a SymbolKind enumerator, but is
/// unsigned to avoid sign extension and achieve better bitpacking with MSVC.
unsigned Kind : 3;
@@ -161,8 +164,8 @@ class MCSymbol {
MCSymbol(SymbolKind Kind, const StringMapEntry<bool> *Name, bool isTemporary)
: IsTemporary(isTemporary), IsRedefinable(false), IsUsed(false),
IsRegistered(false), IsExternal(false), IsPrivateExtern(false),
- Kind(Kind), IsUsedInReloc(false), SymbolContents(SymContentsUnset),
- CommonAlignLog2(0), Flags(0) {
+ IsWeakExternal(false), Kind(Kind), IsUsedInReloc(false),
+ SymbolContents(SymContentsUnset), CommonAlignLog2(0), Flags(0) {
Offset = 0;
HasName = !!Name;
if (Name)
@@ -393,8 +396,10 @@ class MCSymbol {
}
MCFragment *getFragment(bool SetUsed = true) const {
- if (Fragment || !isVariable())
+ if (Fragment || !isVariable() || isWeakExternal())
return Fragment;
+ // If the symbol is a non-weak alias, get information about
+ // the aliasee. (Don't try to resolve weak aliases.)
Fragment = getVariableValue(SetUsed)->findAssociatedFragment();
return Fragment;
}
@@ -405,6 +410,8 @@ class MCSymbol {
bool isPrivateExtern() const { return IsPrivateExtern; }
void setPrivateExtern(bool Value) { IsPrivateExtern = Value; }
+ bool isWeakExternal() const { return IsWeakExternal; }
+
/// print - Print the value to the stream \p OS.
void print(raw_ostream &OS, const MCAsmInfo *MAI) const;
diff --git a/llvm/include/llvm/MC/MCSymbolCOFF.h b/llvm/include/llvm/MC/MCSymbolCOFF.h
index b25993c32db6d..7983fff7e6afd 100644
--- a/llvm/include/llvm/MC/MCSymbolCOFF.h
+++ b/llvm/include/llvm/MC/MCSymbolCOFF.h
@@ -23,8 +23,9 @@ class MCSymbolCOFF : public MCSymbol {
SF_ClassMask = 0x00FF,
SF_ClassShift = 0,
- SF_WeakExternal = 0x0100,
- SF_SafeSEH = 0x0200,
+ SF_SafeSEH = 0x0100,
+ SF_WeakExternalCharacteristicsMask = 0x0E00,
+ SF_WeakExternalCharacteristicsShift = 9,
};
public:
@@ -45,11 +46,16 @@ class MCSymbolCOFF : public MCSymbol {
modifyFlags(StorageClass << SF_ClassShift, SF_ClassMask);
}
- bool isWeakExternal() const {
- return getFlags() & SF_WeakExternal;
+ COFF::WeakExternalCharacteristics getWeakExternalCharacteristics() const {
+ return static_cast<COFF::WeakExternalCharacteristics>((getFlags() & SF_WeakExternalCharacteristicsMask) >>
+ SF_WeakExternalCharacteristicsShift);
}
- void setIsWeakExternal() const {
- modifyFlags(SF_WeakExternal, SF_WeakExternal);
+ void setWeakExternalCharacteristics(COFF::WeakExternalCharacteristics Characteristics) const {
+ modifyFlags(Characteristics << SF_WeakExternalCharacteristicsShift,
+ SF_WeakExternalCharacteristicsMask);
+ }
+ void setIsWeakExternal(bool WeakExt) const {
+ IsWeakExternal = WeakExt;
}
bool isSafeSEH() const {
diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp
index e3d11a2a33744..de48c9e965f14 100644
--- a/llvm/lib/MC/MCAsmStreamer.cpp
+++ b/llvm/lib/MC/MCAsmStreamer.cpp
@@ -773,6 +773,9 @@ bool MCAsmStreamer::emitSymbolAttribute(MCSymbol *Symbol,
case MCSA_Memtag:
OS << "\t.memtag\t";
break;
+ case MCSA_WeakAntiDep:
+ OS << "\t.weak_anti_dep\t";
+ break;
}
Symbol->print(OS, MAI);
diff --git a/llvm/lib/MC/MCELFStreamer.cpp b/llvm/lib/MC/MCELFStreamer.cpp
index 8dd002fba0e1a..303eb16011d17 100644
--- a/llvm/lib/MC/MCELFStreamer.cpp
+++ b/llvm/lib/MC/MCELFStreamer.cpp
@@ -216,6 +216,7 @@ bool MCELFStreamer::emitSymbolAttribute(MCSymbol *S, MCSymbolAttr Attribute) {
case MCSA_Invalid:
case MCSA_IndirectSymbol:
case MCSA_Exported:
+ case MCSA_WeakAntiDep:
return false;
case MCSA_NoDeadStrip:
diff --git a/llvm/lib/MC/MCExpr.cpp b/llvm/lib/MC/MCExpr.cpp
index 210ed0f869292..fc2c3ee8fdd53 100644
--- a/llvm/lib/MC/MCExpr.cpp
+++ b/llvm/lib/MC/MCExpr.cpp
@@ -761,6 +761,9 @@ bool MCExpr::evaluateAsValue(MCValue &Res, const MCAsmLayout &Layout) const {
}
static bool canExpand(const MCSymbol &Sym, bool InSet) {
+ if (Sym.isWeakExternal())
+ return false;
+
const MCExpr *Expr = Sym.getVariableValue();
const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr);
if (Inner) {
diff --git a/llvm/lib/MC/MCMachOStreamer.cpp b/llvm/lib/MC/MCMachOStreamer.cpp
index 82cfcc3ac76cc..d7d343f15eaa6 100644
--- a/llvm/lib/MC/MCMachOStreamer.cpp
+++ b/llvm/lib/MC/MCMachOStreamer.cpp
@@ -358,6 +358,7 @@ bool MCMachOStreamer::emitSymbolAttribute(MCSymbol *Sym,
case MCSA_LGlobal:
case MCSA_Exported:
case MCSA_Memtag:
+ case MCSA_WeakAntiDep:
return false;
case MCSA_Global:
diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index 472f55af84014..7f0f316b33820 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -6371,7 +6371,7 @@ static bool isSymbolUsedInExpression(const MCSymbol *Sym, const MCExpr *Value) {
case MCExpr::SymbolRef: {
const MCSymbol &S =
static_cast<const MCSymbolRefExpr *>(Value)->getSymbol();
- if (S.isVariable())
+ if (S.isVariable() && !S.isWeakExternal())
return isSymbolUsedInExpression(Sym, S.getVariableValue());
return &S == Sym;
}
diff --git a/llvm/lib/MC/MCParser/COFFAsmParser.cpp b/llvm/lib/MC/MCParser/COFFAsmParser.cpp
index fc3d1e94e49f7..3f88257d37db9 100644
--- a/llvm/lib/MC/MCParser/COFFAsmParser.cpp
+++ b/llvm/lib/MC/MCParser/COFFAsmParser.cpp
@@ -67,6 +67,7 @@ class COFFAsmParser : public MCAsmParserExtension {
addDirectiveHandler<&COFFAsmParser::ParseDirectiveLinkOnce>(".linkonce");
addDirectiveHandler<&COFFAsmParser::ParseDirectiveRVA>(".rva");
addDirectiveHandler<&COFFAsmParser::ParseDirectiveSymbolAttribute>(".weak");
+ addDirectiveHandler<&COFFAsmParser::ParseDirectiveSymbolAttribute>(".weak_anti_dep");
addDirectiveHandler<&COFFAsmParser::ParseDirectiveCGProfile>(".cg_profile");
// Win64 EH directives.
@@ -281,6 +282,7 @@ bool COFFAsmParser::ParseSectionFlags(StringRef SectionName,
bool COFFAsmParser::ParseDirectiveSymbolAttribute(StringRef Directive, SMLoc) {
MCSymbolAttr Attr = StringSwitch<MCSymbolAttr>(Directive)
.Case(".weak", MCSA_Weak)
+ .Case(".weak_anti_dep", MCSA_WeakAntiDep)
.Default(MCSA_Invalid);
assert(Attr != MCSA_Invalid && "unexpected symbol attribute directive!");
if (getLexer().isNot(AsmToken::EndOfStatement)) {
diff --git a/llvm/lib/MC/MCWinCOFFStreamer.cpp b/llvm/lib/MC/MCWinCOFFStreamer.cpp
index 36b29b792420f..e510e1e4031cd 100644
--- a/llvm/lib/MC/MCWinCOFFStreamer.cpp
+++ b/llvm/lib/MC/MCWinCOFFStreamer.cpp
@@ -115,9 +115,14 @@ bool MCWinCOFFStreamer::emitSymbolAttribute(MCSymbol *S,
default: return false;
case MCSA_WeakReference:
case MCSA_Weak:
- Symbol->setIsWeakExternal();
+ Symbol->setWeakExternalCharacteristics(COFF::IMAGE_WEAK_EXTERN_SEARCH_ALIAS);
Symbol->setExternal(true);
break;
+ case MCSA_WeakAntiDep:
+ Symbol->setWeakExternalCharacteristics(COFF::IMAGE_WEAK_EXTERN_ANTI_DEPENDENCY);
+ Symbol->setExternal(true);
+ Symbol->setIsWeakExternal(true);
+ break;
case MCSA_Global:
Symbol->setExternal(true);
break;
diff --git a/llvm/lib/MC/WinCOFFObjectWriter.cpp b/llvm/lib/MC/WinCOFFObjectWriter.cpp
index 7b56276744394..2e9b4807f7ccf 100644
--- a/llvm/lib/MC/WinCOFFObjectWriter.cpp
+++ b/llvm/lib/MC/WinCOFFObjectWriter.cpp
@@ -385,7 +385,7 @@ void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &MCSym,
}
COFFSymbol *Local = nullptr;
- if (cast<MCSymbolCOFF>(MCSym).isWeakExternal()) {
+ if (cast<MCSymbolCOFF>(MCSym).getWeakExternalCharacteristics()) {
Sym->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
Sym->Section = nullptr;
@@ -407,9 +407,9 @@ void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &MCSym,
Sym->Aux.resize(1);
memset(&Sym->Aux[0], 0, sizeof(Sym->Aux[0]));
Sym->Aux[0].AuxType = ATWeakExternal;
- Sym->Aux[0].Aux.WeakExternal.TagIndex = 0;
+ Sym->Aux[0].Aux.WeakExternal.TagIndex = 0; // Filled in later
Sym->Aux[0].Aux.WeakExternal.Characteristics =
- COFF::IMAGE_WEAK_EXTERN_SEARCH_ALIAS;
+ cast<MCSymbolCOFF>(MCSym).getWeakExternalCharacteristics();
} else {
if (!Base)
Sym->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
diff --git a/llvm/test/MC/COFF/addrsig.s b/llvm/test/MC/COFF/addrsig.s
index 7c3b25d52edae..a181bb06508be 100644
--- a/llvm/test/MC/COFF/addrsig.s
+++ b/llvm/test/MC/COFF/addrsig.s
@@ -3,7 +3,7 @@
// CHECK: Name: .llvm_addrsig
// CHECK-NEXT: VirtualSize: 0x0
// CHECK-NEXT: VirtualAddress: 0x0
-// CHECK-NEXT: RawDataSize: 4
+// CHECK-NEXT: RawDataSize: 6
// CHECK-NEXT: PointerToRawData:
// CHECK-NEXT: PointerToRelocations: 0x0
// CHECK-NEXT: PointerToLineNumbers: 0x0
@@ -46,6 +46,8 @@
// CHECK-NEXT: Sym: g3 (11)
// CHECK-NEXT: Sym: local (10)
// CHECK-NEXT: Sym: .data (2)
+// CHECK-NEXT: Sym: weak_sym (12)
+// CHECK-NEXT: Sym: .data (2)
// CHECK-NEXT: ]
.globl g1
@@ -64,3 +66,10 @@ local:
.data
.Llocal:
+
+.weak weak_sym
+weak_sym:
+.addrsig_sym weak_sym
+
+.set .Lalias_weak_sym, weak_sym
+.addrsig_sym .Lalias_weak_sym
diff --git a/llvm/test/MC/COFF/weak-anti-dep.s b/llvm/test/MC/COFF/weak-anti-dep.s
new file mode 100644
index 0000000000000..dbf5ffc0a35bf
--- /dev/null
+++ b/llvm/test/MC/COFF/weak-anti-dep.s
@@ -0,0 +1,68 @@
+// RUN: llvm-mc -filetype=obj -triple x86_64-pc-win32 %s | llvm-readobj --symbols - | FileCheck %s
+
+// CHECK: Symbol {
+// CHECK-NEXT: Name: .text
+// CHECK: Symbol {
+// CHECK-NEXT: Name: .data
+// CHECK: Symbol {
+// CHECK-NEXT: Name: .bss
+
+.weak_anti_dep a
+a = b
+
+// CHECK: Symbol {
+// CHECK-NEXT: Name: a
+// CHECK-NEXT: Value: 0
+// CHECK-NEXT: Section: IMAGE_SYM_UNDEFINED (0)
+// CHECK-NEXT: BaseType: Null (0x0)
+// CHECK-NEXT: ComplexType: Null (0x0)
+// CHECK-NEXT: StorageClass: WeakExternal (0x69)
+// CHECK-NEXT: AuxSymbolCount: 1
+// CHECK-NEXT: AuxWeakExternal {
+// CHECK-NEXT: Linked: b (8)
+// CHECK-NEXT: Search: AntiDependency (0x4)
+// CHECK-NEXT: }
+// CHECK-NEXT: }
+// CHECK-NEXT: Symbol {
+// CHECK-NEXT: Name: b
+// CHECK-NEXT: Value: 0
+// CHECK-NEXT: Section: IMAGE_SYM_UNDEFINED (0)
+// CHECK-NEXT: BaseType: Null (0x0)
+// CHECK-NEXT: ComplexType: Null (0x0)
+// CHECK-NEXT: StorageClass: External (0x2)
+// CHECK-NEXT: AuxSymbolCount: 0
+// CHECK-NEXT: }
+
+
+.weak_anti_dep r1
+.weak_anti_dep r2
+r1 = r2
+r2 = r1
+
+
+// CHECK: Symbol {
+// CHECK-NEXT: Name: r1
+// CHECK-NEXT: Value: 0
+// CHECK-NEXT: Section: IMAGE_SYM_UNDEFINED (0)
+// CHECK-NEXT: BaseType: Null (0x0)
+// CHECK-NEXT: ComplexType: Null (0x0)
+// CHECK-NEXT: StorageClass: WeakExternal (0x69)
+// CHECK-NEXT: AuxSymbolCount: 1
+// CHECK-NEXT: AuxWeakExternal {
+// CHECK-NEXT: Linked: r2 (11)
+// CHECK-NEXT: Search: AntiDependency (0x4)
+// CHECK-NEXT: }
+// CHECK-NEXT: }
+// CHECK-NEXT: Symbol {
+// CHECK-NEXT: Name: r2
+// CHECK-NEXT: Value: 0
+// CHECK-NEXT: Section: IMAGE_SYM_UNDEFINED (0)
+// CHECK-NEXT: BaseType: Null (0x0)
+// CHECK-NEXT: ComplexType: Null (0x0)
+// CHECK-NEXT: StorageClass: WeakExternal (0x69)
+// CHECK-NEXT: AuxSymbolCount: 1
+// CHECK-NEXT: AuxWeakExternal {
+// CHECK-NEXT: Linked: r1 (9)
+// CHECK-NEXT: Search: AntiDependency (0x4)
+// CHECK-NEXT: }
+// CHECK-NEXT: }
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