[llvm] fffdb7e - [COFF] Add MC support for emitting IMAGE_WEAK_EXTERN_ANTI_DEPENDENCY symbols
Eli Friedman via llvm-commits
llvm-commits at lists.llvm.org
Fri Apr 7 14:07:02 PDT 2023
Author: Eli Friedman
Date: 2023-04-07T14:05:45-07:00
New Revision: fffdb7eac58b4efde5e23c1281e7a7f93a42d280
URL: https://github.com/llvm/llvm-project/commit/fffdb7eac58b4efde5e23c1281e7a7f93a42d280
DIFF: https://github.com/llvm/llvm-project/commit/fffdb7eac58b4efde5e23c1281e7a7f93a42d280.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 required a few
changes to the way we handle weak symbols on Windows.
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/alias.s
Removed:
################################################################################
diff --git a/llvm/include/llvm/MC/MCDirectives.h b/llvm/include/llvm/MC/MCDirectives.h
index b9668a0c994f..19d54b5d5ef7 100644
--- a/llvm/include/llvm/MC/MCDirectives.h
+++ b/llvm/include/llvm/MC/MCDirectives.h
@@ -47,6 +47,7 @@ enum MCSymbolAttr {
MCSA_WeakReference, ///< .weak_reference (MachO)
MCSA_WeakDefAutoPrivate, ///< .weak_def_can_be_hidden (MachO)
MCSA_Memtag, ///< .memtag (ELF)
+ MCSA_WeakAntiDep, ///< .weak_anti_dep (COFF)
};
enum MCAssemblerFlag {
diff --git a/llvm/include/llvm/MC/MCSymbol.h b/llvm/include/llvm/MC/MCSymbol.h
index 8954960e3b8c..22f2a1d7210c 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;
FragmentAndHasName.setInt(!!Name);
if (Name)
@@ -407,6 +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 94087ce871ae..32f55cd1e4c3 100644
--- a/llvm/include/llvm/MC/MCSymbolCOFF.h
+++ b/llvm/include/llvm/MC/MCSymbolCOFF.h
@@ -22,8 +22,9 @@ 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:
@@ -44,11 +45,14 @@ 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 setIsWeakExternal(COFF::WeakExternalCharacteristics Characteristics) const {
+ IsWeakExternal = true;
+ modifyFlags(Characteristics << SF_WeakExternalCharacteristicsShift,
+ SF_WeakExternalCharacteristicsMask);
}
bool isSafeSEH() const {
diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp
index c11d28b746f6..6f21566a50f2 100644
--- a/llvm/lib/MC/MCAsmStreamer.cpp
+++ b/llvm/lib/MC/MCAsmStreamer.cpp
@@ -772,6 +772,9 @@ 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 8dd002fba0e1..303eb16011d1 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 04682fdc7ece..5c061b53a28d 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) {
@@ -997,6 +1000,8 @@ MCFragment *MCExpr::findAssociatedFragment() const {
case SymbolRef: {
const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
const MCSymbol &Sym = SRE->getSymbol();
+ if (Sym.isWeakExternal())
+ return nullptr;
return Sym.getFragment();
}
diff --git a/llvm/lib/MC/MCMachOStreamer.cpp b/llvm/lib/MC/MCMachOStreamer.cpp
index 986c0c2c506b..6711ff9001a3 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 c49e51332b12..254c747aca05 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 fc3d1e94e49f..3f88257d37db 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 c9a968164834..ad0b1c157278 100644
--- a/llvm/lib/MC/MCWinCOFFStreamer.cpp
+++ b/llvm/lib/MC/MCWinCOFFStreamer.cpp
@@ -115,7 +115,11 @@ bool MCWinCOFFStreamer::emitSymbolAttribute(MCSymbol *S,
default: return false;
case MCSA_WeakReference:
case MCSA_Weak:
- Symbol->setIsWeakExternal();
+ Symbol->setIsWeakExternal(COFF::IMAGE_WEAK_EXTERN_SEARCH_ALIAS);
+ Symbol->setExternal(true);
+ break;
+ case MCSA_WeakAntiDep:
+ Symbol->setIsWeakExternal(COFF::IMAGE_WEAK_EXTERN_ANTI_DEPENDENCY);
Symbol->setExternal(true);
break;
case MCSA_Global:
diff --git a/llvm/lib/MC/WinCOFFObjectWriter.cpp b/llvm/lib/MC/WinCOFFObjectWriter.cpp
index 4927ea6177fd..6687fd6af9c8 100644
--- a/llvm/lib/MC/WinCOFFObjectWriter.cpp
+++ b/llvm/lib/MC/WinCOFFObjectWriter.cpp
@@ -414,9 +414,9 @@ 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/alias.s b/llvm/test/MC/COFF/alias.s
index b6828c658132..cfb44ca1503f 100644
--- a/llvm/test/MC/COFF/alias.s
+++ b/llvm/test/MC/COFF/alias.s
@@ -24,7 +24,7 @@ weak_aliased_to_external = external2
// CHECK: 0x0 IMAGE_REL_I386_DIR32 external_aliased_to_local
// CHECK: 0x4 IMAGE_REL_I386_DIR32 external1
// CHECK: 0x8 IMAGE_REL_I386_DIR32 global_aliased_to_local
-// CHECK: 0xC IMAGE_REL_I386_DIR32 external2
+// CHECK: 0xC IMAGE_REL_I386_DIR32 weak_aliased_to_external
// CHECK: ]
// CHECK: Symbols [
// CHECK-NEXT: Symbol {
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 000000000000..dbf5ffc0a35b
--- /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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